Bronchiectasis - Monograph 2011

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Guest Editors

R.A. Floto

R.A. Floto is a Principle Investigator and Wellcome Trust Senior Clinical Fellow at the Cambridge Institute for Medical Research, University of Cambridge(Cambridge, UK). His laboratory, funded by the Wellcome Trust and MedicalResearch Council (UK), is focussed on understanding how the immune system

interacts with bacterial and mycobacterial pathogens to trigger inflammatory lung damage. He is head of research at the Cambridge Centre for Lung Infectiondirecting clinical and translational studies on CF and non-CF bronchiectasisand is an Honorary Consultant at Papworth Hospital and Addenbrooke’sHospital (both Cambridge). Recent honours received include the BUPAFoundation Researcher of the Year award (2010) and the European Respiratory Society Maurizio Vignola Award for Innovation in Pulmonology (2007).

C.S. Haworth

C.S. Haworth is Director of the Cambridge Centre for Lung Infection(incorporating The Adult Cystic Fibrosis Centre, The Lung Defence Clinic andThe Immunology Clinic) at Papworth Hospital (Cambridge, UK). He is also an

Honorary Consultant at Addenbrooke’s Hospital in Cambridge. The LungDefence Clinic oversees the care of more than 1,000 patients with bronchiectasisassociated with primary and secondary immunodeficiency syndromes,nontuberculous mycobacterial (NTM) disease, Aspergillus-related lung disease,rheumatoid arthritis, serious childhood infection, chronic aspiration andprimary ciliary dyskinesia. C.S. Haworth trained at the Royal BromptonHospital and the Hammersmith Hospital in London (UK), before moving toCambridge in 2003. He is a co-author of the North American Cystic FibrosisFoundation/the UK Cystic Fibrosis Trust/European Cystic Fibrosis Society Bone Health Guidelines and is co-chair (with R.A. Floto) of the EuropeanCystic Fibrosis Society NTM working group. He collaborates with several

research groups at the University of Cambridge and is the chief investigator of multicentre, novel therapy, clinical trials in cystic fibrosis (CF) and non-CFbronchiectasis.

Eur Respir Mon 2011. 52, v.Printed in UK – all rights reserved.Copyright ERS 2011.European Respiratory Monograph;ISSN: 1025-448x.DOI: 10.1183/1025448x.10004811

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Preface

B ronchiectasis has been a well-known disease for a long time. Followingthe introduction of antibiotic treatment in clinical practice for

respiratory tract infections, the problem of bronchiectasis appeared to besolved, with some exceptions, e.g. in diseases such as cystic fibrosis. However,

bronchiectasis is associated with a number of immunological diseases andoccurs as a long-term complication of chronic lung diseases. These types of diseases, mainly chronic obstructive pulmonary disease, have become moreand more prevalent, which has again made bronchiectasis a disease of interest. Unfortunately, most of the evidence regarding bronchiectasis isfrom case series and uncontrolled studies. Bronchiectasis has not been afocus of the pharmaceutical industry and randomised controlled studies havenever been performed. Specific guidelines focusing on bronchiectasis are yetto be published.

Over the past few years the scene has changed dramatically. Bronchiectasis isnow a hot topic for epidemiological, basic and clinical research. A number of drugs, such as inhaled antibiotics and substances improving sputumclearance, are now available in a clinical development programme, the firstresults of which will be presented later this year. Therefore, now is the time tosummarise the current knowledge about bronchiectasis.

The Guest Editors of this Monograph have succeeded in attracting leadingexperts within the field to write chapters which provide an overview fromcurrent pathophysiology, diagnostics and treatment to future developmentsthat are on the horizon.

I want to congratulate the Guest Editors for this excellent Monograph, whichwill be of interest and use to basic scientists and clinicians in their daily practice.

Editor in Chief T. Welte

Eur Respir Mon 2011. 52, vi. Printed in UK – all rights reserved, Copyright ERS 2011. European Respiratory Monograph;ISSN: 1025-448x. DOI: 10.1183/1025448x.10005111

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Introduction

R.A. Floto* ,# and C.S. Haworth #

*Cambridge Institute for Medical Research, University of Cambridge, and # Cambridge Centre for Lung Infection, Papworth Hospital, Cambridge, UK.

Correspondence: R.A. Floto, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK, Email: [email protected]

S ince its first description in the 19th century, bronchiectasis remains a clinically important, butpoorly understood condition. This issue of the European Respiratory Monograph (ERM ) brings

together contributions from leading international experts on the subject of non-cystic fibrosis(CF)-associated bronchiectasis in adults. This issue of the ERM discusses the epidemiology andaetiology of the condition and describes the associated changes in histopathology and radiology. Itexplores the basic mechanisms controlling lung inflammation and immunity and how these can bedisrupted to trigger bronchiectasis. In this Monograph, we define appropriate investigationalgorithms, explore the role of bacteria, viruses, fungi and nontuberculous mycobacteria, and

discuss the specific features of bronchiectasis associated with ciliary dyskinesias, channelopathies,inflammatory bowel disease, immunodeficiencies and autoimmune disease. This Monographdetails the various treatment modalities available for bronchiectasis, including antibiotic regimens,the use of macrolides and other anti-inflammatory agents, airway clearance strategies and the roleof surgery.

This issue of the ERM offers a comprehensive and cutting edge review of non-CF-associatedbronchiectasis and provides a definitive guide to the management of this challenging condition.

Eur Respir Mon 2011. 52, vii. Printed in UK – all rights reserved, Copyright ERS 2011. European Respiratory Monograph;ISSN: 1025-448x. DOI: 10.1183/1025448x.10004911

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Chapter 1

Bronchiectasis:

epidemiology and

causesD. Bilton* ,#," and A.L. Jones* ,#,"

Summary Bronchiectasis remains a significant cause of morbidity andmortality in the developed world. The true prevalence of thecondition remains elusive, in part, because of the innatedifficulty in determining causation, when more than onerespiratory condition exists in the same patient, but also due tothe increasing rate of diagnosis by radiological means where noclinical symptoms are present. The wide ranging aetiology of

bronchiectasis will be discussed in this chapter; however, someaspects will be discussed in greater detail throughout thisMonograph.

The diagnosis of bronchiectasis should be the beginning of atargeted search for causation, which may lead to directedtreatment, thereby limiting the disease progression. Over thenext 5 years a reduction in the number of cases labelled asidiopathic bronchiectasis should be expected, as the continualexpanding knowledge of immunology and immunogenetics, with respect to large studies of patients with bronchiectasis, canbe applied.

Keywords: Aetiology, bronchiectasis, epidemiology, non-cysticfibrosis

*Dept of Cystic Fibrosis, RoyalBrompton Hospital,#NIHR Biomedical Research Unitinto Advanced Lung Disease, RoyalBrompton Hospital, and"Dept of Cystic Fibrosis, NationalHeart and Lung Institute, ImperialCollege London, London, UK.

Correspondence: D. Bilton, RoyalBrompton Hospital, Sydney Street,London, SW3 6NP, UK, [email protected]

Eur Respir Mon 2011. 52, 1–10.Printed in UK – all rights reserved.Copyright ERS 2011.European Respiratory Monograph;ISSN: 1025-448x.DOI: 10.1183/1025448x.10003110

Bronchiectasis was first described by Laennec [1] in 1819 as part of a wider work describing theuse of his novel invention, the stethoscope. In his book ‘‘De l’Auscultation Mediate ou Traite du

Diagnostic des Maladies des Poumons et du Coeur’’ [1], he described the condition through the use of case reports, detailing clinical examination and correlating this with post mortem findings. He

identified that any illness characterised by chronic sputum production could lead to bronchiectasiswith tuberculosis and pertussis infection identified as the most likely causative conditions.

A century later, in 1919, A. Jex-Blake delivered a lecture at the Hospital for Consumption(London, UK) on the condition of bronchiectasis [2]. He examined the case records for thehospital over a 20-year period and gave a detailed account of the condition and its causes. Heidentified that bronchiectasis itself was a secondary condition to a preceding disorder of the lung and,

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as such, its frequency was likely to be underestimated as the preceding condition was of suchseverity that the presence of bronchiectasis was overlooked. He also identified that the conditionwas apparent in 2% of the hospital’s admissions over the same 20-year period, but estimated thatthe true figure could be as high as 5%. Perhaps, unsurprisingly, in this pre-antibiotic era a third of patients were identified as having bronchiectasis secondary to an episode of pneumonia or pleurisy,a third due to chronic bronchitis and a further third due to bronchial obstruction, the majority of which were malignant tumours.

Since the introduction of antibiotic therapy the incidence of bronchiectasis due to tuberculosis or otherinfections decreased markedly from the beginning of the 20th century. Perhaps the most strikingevidence for the effect of antibiotic introduction was a report in 1969 by F IELD [3] into childhoodadmissions for the condition. The author reported a reduction from 24–99 per 10,000 hospitaladmissions to 6–13 per 10,000 admissions for five large children’s hospitals between 1952 and 1960.

Despite this decline in cases in the antibiotic era of medicine, non-cystic fibrosis (CF)bronchiectasis remains a significant cause of morbidity.

Epidemiology Remarkably the current knowledge of the true incidence of bronchiectasis has changed very littlefrom when A. Jex-Blake gave his lecture almost a century ago. In part, the reason for this remainssimilar to what was perceived in 1919. Bronchiectasis is often noted as a secondary phenomenonto a more severe pulmonary pathology, as is the case of asthma or chronic obstructive pulmonary disease (COPD), and as such goes unreported. Conversely, the widespread use of computertomography (CT) as a diagnostic tool in respiratory medicine has resulted in the identification of an increased number of radiological bronchiectasis cases in patients who showed no symptomsand who would have otherwise not been classified as having it. Future studies of the prevalence of bronchiectasis should not be confined to radiological evidence alone but should include theassessment of clinical symptoms.

One of the first large-scale studies to determine the incidence of bronchiectasis was performed in1953 and examined the population of Bedford, a town in the UK [4]. The authors identified anincidence of bronchiectasis as 1.3 per 1,000 people. The relevance of this data, collected prior tothe widespread use of antibiotics and where the authors excluded patients with bronchiectasis as aconsequence of other pulmonary pathology, is perhaps limiting. However, more recent data hasbeen collected from cohorts in Finland, New Zealand and the USA [5–7]. The data from Finlandsuggested an incidence of 2.7 per 100,000 people, while in New Zealand an overall incidence inchildren of 3.7 per 100,000 was noted but showed wide variations with regards ethnicity. For

example, children from a Pacific Island descent had an incidence of 17.8 per 100,000 comparedwith an incident of 1.5 per 100,000 for those of a Northern European descent.

Unsurprisingly, given the often chronic nature of its development, the prevalence of bronchiectasisand hospital admission related to bronchiectasis increased with age. Studies from the USAestimate a prevalence of 4.2 per 100,000 people in those aged 18–34 years, increasing to 271.8 per100,000 in people aged .75 years [7].

Aetiology

There are a wide range of conditions that can cause bronchiectasis and there are a number of waysin which one could classify these aetiological factors; however, an approach based on pathologicalprocesses appears to be the most logical and is described in table 1.

Bronchial dilatation can be caused by a structural defect in the wall itself, an effect of abnormalairway pressure on the bronchial wall or by damage to the airway elastic tissue and cartilage as aresult of bronchial wall inflammation.

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Inflammation within the bronchial wallcan be the result of an infection withinthe airway, inhalation of injurious agentsor an endogenous condition such as anautoimmune disease.

The lungs are continuously exposed to

inhaled pathogens and have developedan advanced mechanism for trappingand removing them. The human airwaysare lined with ciliated epithelium withsubmucosal goblet cells secreting mucusthat makes up the top layer of the airway surface liquid, the lower layer being thepericiliary fluid that bathes the cilia andensures they function appropriately. Inhealthy individuals the mucus trapsinhaled pathogens and the continuously motile cilia transport the mucus and itscontents out of the lung. Any defect inthis mucociliary clearance mechanismcan lead to the retention of pathogensresulting in the progression of airway infection, inflammation and ultimately bronchiectasis.

Structural lung conditions

The effect of obstructions within the bron-chus itself was identified by LAENNEC [1]as a significant cause of bronchiectasis.Obstruction of the bronchi with foreignobjects or tumours is now a relatively rarecause of bronchiectasis. Unsurprisingly most patients with bronchiectasis second-ary to retained objects are young children.

Congenital disorders affecting the struc-

ture of the bronchial tree can lead tobronchiectasis through a direct effect onthe bronchial wall itself, although im-paired clearance of sputum through theabnormally dilated structures can fur-ther compound the condition.

Williams–Campbell syndrome was firstdescribed in 1960 after the case reports of five children were studied by WILLIAMS

andCAMPBELL [8]. Histological examination of the bronchial wall revealed a deficiency or absence of

cartilage, mostly from the third division of the bronchi down. WILLIAMS andCAMPBELL [8]went on todescribe a further 11 children with the same clinical findings of bronchiectasis and cartilagedeficiency.

Mounier–Kuhn syndrome (tracheobronchomegaly) is characterised by dilatation of the tracheaand large bronchi, usually presenting in young adults. Its underlying pathology is not clearly understood but histological examination has shown atrophy of airway cartilage and smooth muscle.

Table 1. Aetiology of bronchiectasis

Structural lung conditions

Williams–Campbell syndrome

Mounier–Kuhn syndromeEhlers–Danlos syndrome

Toxic damage to airways

Inhalational injury

Aspiration secondary to neuromuscular diseaseGERD

Obstruction of single bronchus

TumourForeign body

Obstructive airways disease

AsthmaCOPD

AAT deficiency

Defects of mucociliary clearance

Ciliary dyskinesia

Primary ciliary dyskinesia

Secondary ciliary dyskinesiaChannelopathies

CFTR dysfunction

ENaC dysfunction

ABPA

Immunodeficiency

CVID

XLA

CGD Antibody deficiency with normal Ig

Secondary immunodeficiency

Haematological malignancy

Post-allogeneic bone marrow transplantDrug-induced immunosuppression

Infections

Childhood infections Tuberculosis

Pneumonia

Measles

Whooping coughNontuberculous mycobacteria

Bronchiectasis in systemic diseases

Inflammatory bowel diseaseConnective tissue diseases

Yellow nail syndromeIdiopathic bronchiectasis

GERD: gastro-oesophageal reflux disease; COPD: chronic

obstructive pulmonary disease; AAT: a1- antitrypsin defi-

ciency; CFTR: cystic fibrosis transmembrane conductanceregulator; ENaC: epithelial sodium channel; ABPA: allergic

bronchopulmonary aspergillosis; CVID: common variable

immunodeficiency; XLA: X-linked agammaglobulinaemia;

CGD: chronic granulomatous disease; Ig: immunoglobulin.

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Case reports suggesting an association with Ehlers–Danlos syndrome, and the appearance of thecondition in siblings, could point to an unidentified genetic cause for the condition.

Obstructive airways disease

To carry on the theme of defects in the gross airway structure itself, perhaps a continuation of thisis to consider whether obstructive airways diseases, namely asthma and COPD, could lead to

bronchiectasis. It is natural to assume that these conditions would lead to bronchiectasis as bothhave clearly been shown to cause airway inflammation and structural blockage of airways, eitherthrough bronchospasm or fixed airways obstruction, in the case of COPD.

Asthma

A number of studies have highlighted the presence of airway remodelling in chronic asthmapatients using high-resolution CT (HRCT) scanning techniques. The airway remodelling can vary from mild airway wall thickening to blatant bronchiectasis. Bronchial wall thickening has beenfound in up to 82% of asthmatic patients in a cohort [9] and in patients with mild asthma [10]. As

bronchial wall thickening is indicative of airway inflammation this suggests that a significantnumber of patients with asthma are at risk of developing bronchiectasis.

The prevalence of bronchiectasis in these studies is estimated at 17.5–40% [9–11]. In the largest of these studies, which comprised of 463 patients with severe asthma, 40% of patients were shown tohave evidence of bronchiectasis on HRCT scans [11]. However, study participants were selected forHRCT on the basis of clinical indication, the most common being a suspicion of bronchiectasis.

The studies suggest that bronchiectasis is associated with a more severe obstruction and is moreapparent in patients who present with a longer history of asthma symptoms, consequently asubgroup of severe asthma patients appear to be at risk of developing bronchiectasis [9–11].

COPD

COPD is a term encompassing a number of pathological processes including chronic bronchitis,asthma, emphysema and bronchiectasis. Therefore, it is difficult to fully attribute COPD as the causeof bronchiectasis as in some cases bronchiectasis may be the primary diagnosis. Certainly it isprobable that bronchiectasis in COPD is common. A study of moderate-to-severe COPD patientsdemonstrated the prevalence of bronchiectasis to be 50% [12]. The COPD patients withbronchiectasis were found to have more severe exacerbations and increased sputum inflammatory markers. Further studies are required to elucidate the mechanisms that predispose COPD patients todeveloping bronchiectasis; severity of airflow obstruction may be a key driver in this mechanism.

a1-antitrypsin deficiency

a1-antitrypsin (AAT) deficiency is classically associated with predominantly lower lobe em-physema. Bronchiectasis has also been associated with the enzyme deficiency, whether this is adirect consequence of the deficiency or secondary to the emphysema-associated airwaysobstruction is less clear. In a study of patients with severe AAT deficiency the vast majority of subjects had some evidence of bronchiectasis on a HRCT scan (70 out of 74 subjects), with 27%having clinically significant bronchiectasis with a correlation between forced expiratory volume in1 second (FEV1) and bronchial wall thickness [13]. In a study of the distribution of AAT alleles ina population of bronchiectasis patients, there was no difference in AAT allele distribution betweenhealthy controls and bronchiectasis patients [14]. However, there was an over representation of hetero- and homozygote AAT deficiency alleles in those patients with bronchiectasis andcoexistent asthma. Therefore, the evidence would suggest that AAT deficiency is related to airway obstruction rather than a direct effect of the enzyme deficiency on the bronchial wall structure.

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Defects of mucociliary clearance

Ciliary dyskinesia

Abnormalities of cilia structure and/or motility cause a decreased mucus clearance from the lungs.These abnormalities can be due to a primary defect in the structure or function of the cilia orsecondary damage to the cilia from external agents, such as bacteria or inhaled noxious agents.


Airway cilia are complicated structures containing more than 250 proteins. The ciliary structuresare composed of microtubules which are mobilised by structures known as dynein arms, these aredivided into two groups the outer and inner dynein arms. This complicated polypeptide structurecan be affected by numerous genetic mutations and, as such, primary ciliary dyskinesia (PCD) is agenetically heterogenous disorder. Among the most commonly identified mutations are those of the genes DNAI1 and DNAH5 , which code for proteins responsible for the assembly of outerdynein arms.

As cilia are present throughout the body, patients with PCD will often present with multiplesymptoms such as sinusitis, recurrent otitis media, infertility and defects of organ lateralisationwith situs inversus or situs ambiguus. The triad of bronchiectasis, chronic sinusitis and situsinversus is also known as Kartagener’s syndrome.

Secondary ciliary dyskinesia

A number of noxious agents, both organic and inorganic, have been shown to affect the functionof cilia in human airway epithelia. Certain bacteria, such as Pseudomonas aeruginosa and

Haemophilus influenzae , have been shown to disable mucociliary clearance by releasing productsthat inhibit ciliary beat frequency, allowing them to persist and propagate infection [15, 16].

Inhaled inorganic substances such as diesel particles [17] and cigarette smoke [18] have also beenshown to have a direct effect on ciliary function, inhibiting ciliary beat frequency. It is importantto note here that no causal role for tobacco smoking and the development of bronchiectasis hasbeen made, indeed outside of COPD bronchiectasis appears to be a disease of the nonsmoker.

Aspiration of gastric contents is a well recognised, but perhaps under diagnosed, cause of bronchiectasis. Whilst aspiration of both acid and nonacid stomach contents leads to directinflammation of the bronchial wall, ciliary function may also be affected by these agents.

Channelopathies

As previously mentioned, the epithelial lining of the airway is coated in a liquid known as theairway surface liquid. It contains two layers, the outer mucus layer and an inner periciliary layer.Ion channels within the apical surface of the epithelial levels regulate the fluid content of this layerto ensure adequate hydration. This enables the cilia to move in a liquid layer but also prevents thedesiccation of the mucus into a thick, sticky substance that is difficult to mobilise.

Defects in the ion channels of the epithelial layer can lead to dehydration of the airway surfaces,thereby affecting the depth of the periciliary layer and bringing the cilia into contact with theviscous mucus layer, further impeding its function. The most widely recognised of these defects isthat found in CF. Here, the loss of a chloride channel known as the CF transmembrane regulator(CFTR) protein leads to the inability of the epithelial cells to excrete chloride. The dysregulation of the ion transport is further compounded by the effect of CFTR on another ion channel, that of theepithelial sodium channel (ENaC). CFTR is an inhibitor of the ENaC channel and therefore theloss of CFTR is postulated to lead to hyperactivity of the sodium channel, resulting in a large

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increase in the transport of sodium into the epithelial cell with a corresponding movement of water out of the airway liquid.

In theory, genetic defects of the ENaC channel could lead to bronchiectasis if such a mutation led toover activity of the channel. Whilst mutations of ENaC genes have been identified in patients withidiopathic bronchiectasis [19], a significant number of these were also carriers of a CFTR mutation.Furthermore, a single CFTR mutation is frequently observed in patients with diffuse bronchiectasis.

A study comparing patients with either none, one or two CFTR mutations suggested a continuum of CFTR dysfunction (as measured by nasal potential differences) existed and that this may lead to thedevelopment of bronchiectasis in some patients who are CFTR heterozygotes [20].

Allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is a pulmonary condition caused by a hyper-sensitivity reaction to the ubiquitous environmental fungus Aspergillus fumigatus . It is mostcommonly seen in patients with pre-existing asthma or CF and is clinically characterised by recurrent wheeze, pulmonary infiltrates and the development of bronchiectasis. The hypersensi-

tivity reaction has mixed features of immediate hypersensitivity (type I), antigen–antibody complexes (type III) and inflammatory cell responses (type IV) [21].

The inflammatory cell response seen in ABPA shows a predominance of T-helper cell type 2 (Th2)cells leading to a release of cytokines mediating allergic inflammation (as opposed to the Th1,cytotoxic pathway) [22]. The type I hypersensitivity reaction causes local degranulation of mastcells and histamine release leading to bronchoconstriction. The combination of airway in-flammation, which leads to viscous, eosinophil-laden mucus, plugging and airway obstruction,and bronchospasm leads to a reduction in mucociliary clearance and the development of bronchiectasis. As such bronchiectasis in ABPA is common. In three large case studies it was foundthat central bronchiectasis was present in 69–76% of patients with ABPA [23–25].

Immunodeficiency

Defects in the immune system leave the lungs vulnerable to infection and in some cases thedevelopment of bronchiectasis can be the first indication of immunodeficiency.

The most common forms of primary immune deficiencies observed in patients with bronchiectasisare common variable immune deficiency (CVID), X-linked agammaglobulinaemia (XLA) andchronic granulomatous disease (CGD).

Common variable immune deficiency

CVID is characterised by reduced levels of immunoglobulins (Igs) with associated recurrent bacterialinfections. An increased risk of autoimmune conditions and malignancy has also been identified. Themajority of patients present with recurrent pulmonary infections at a mean age 29 years [26]. CVID isthe most common primary immune deficiency to cause bronchiectasis. A case series undertaken in aUK population identified 68% of the patients with CVID as having evidence of bronchiectasis [27].The most likely cause of this high rate of incidence could be the delay in the diagnosis of CVID, with amean duration of 4 years between reporting of symptoms and diagnosis [27].

X-linked agammaglobulinaemia

XLA is caused by a mutation of a tyrosine kinase gene that is involved in the development of B-lymphocytes, leading to an absence of circulating B-lymphocytes and the absence of Igs. Given theseverity of the immune deficiency it usually presents much earlier than CVID, usually beingdiagnosed in early childhood [28]. Despite treatment with replacement Igs, chronic lung diseasecan still develop with the risk of developing bronchiectasis increasing with age [29].

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Chronic granulomatous disease

CGD is a group of disorders characterised by a loss of phagocytic NADPH oxidase, without whichphagocytes are unable to produce the reactive oxygen species required to kill ingested bacteria.Infections are mainly due to Staphylococcus aureus , Serratia marcescens , Salmonella sp., Klebsiella sp. and Burkholderia cepacia .

Antibody deficiency with normal Igs

In a study of patients with bronchiectasis and normal IgG levels, 11% were shown to have specificantibody production deficiencies with an inability to respond to pneumococcal and H. influenzae vaccines [30].

Secondary immunodeficiency

The development of bronchiectasis in HIV-infected patients has been noted in a number of caseseries. While recurrent pulmonary infection is likely to be the major factor in the development of

bronchiectasis in these patients, the development of lymphocytic interstitial pneumonia may alsobe implicated [31].

Infections

Childhood infections

A number of childhood respiratory infections have been implicated in the pathogenesis of bronchiectasis. The most widely recognised infectious causes of bronchiectasis are measles andpertussis infection in the West [32], with tuberculosis being a major cause elsewhere.

Nontuberculous mycobacterial infection

Globally, Mycobacterium tuberculosis infection remains a major cause of morbidity and mortality and a significant cause of bronchiectasis. In developed countries with screening programmes andadequate access to treatment, the incidence of new infections remains low. However, the incidence of nontuberculous mycobacterial (NTM) pulmonary infections is increasing. These mycobacteria vary in pathogenecity with Mycobacterium avium complex (MAC) being the most pathogenic whilstother organisms, such as Mycobacterium gordonae and Mycobacterium abscessus, act as opportunisticpathogens and are only found in patients with underlying lung diseases. NTM is commonly present

in one of three clinical forms; 1) a tuberculosis-like pattern with a predominant upper lobefibrocavitatory disease, mostly found in older males with COPD; 2) nodular bronchiectasis, mostcommonly seen in middle-aged females; and 3) hypersensitivity pneumonitis [33].

The second of these clinical forms is also known as ‘‘Lady Windermere syndrome’’, and was firstdescribed in 1992 in a case series of 29 predominately elderly, female patients [34]. The patients hadMAC infection with bronchiectasis predominantly affecting the middle lobe and lingula. Theauthors postulated that persistent voluntary cough suppression could lead to chronic inflammatory processes in these poorly draining lung regions which are susceptible to MAC infection [34].

Bronchiectasis in systemic diseases

Inflammatory bowel disease

The development of bronchiectasis in patients with ulcerative colitis is a well recognisedphenomenon and the subject of a number of case series [35]. Classically, bronchiectasis developsafter resection of the large bowel, suggesting a common immune system response that becomes

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concentrated on the bronchial wall after the bowel is removed. The common embryonic originand similar structures of bowel and bronchial wall (columnar epithelial and submucosal glands)add weight to this theory.

The link between Crohn’s disease and bronchiectasis is less clear with only a small number of casereports detailing their coexistence [36], perhaps too few to determine a definite association.

Connective tissue diseasesA number of connective tissue diseases have been noted to be associated with bronchiectasis,largely based on case series reviews of small numbers of patients. The clearest association is thatbetween rheumatoid arthritis and bronchiectasis. Studies have estimated the incidence of bronchiectasis in rheumatoid arthritis patients to be as high as 41% with a significant number of them being asymptomatic [37]. Again no clear pathological process has been identified as thecause of this association, although studies have suggested common genetic predisposition with anassociation between human leukocyte antigen sub-groups [38]. An effect of the immunosup-pressive agents used in rheumatoid arthritis treatment has also been postulated, although asignificant number of patients develop bronchiectasis prior to the onset of arthropathy.Associations between bronchiectasis and Sjogren’s syndrome [39], systemic sclerosis [40], systemiclupus erythematosus [41], ankylosing spondylitis [42, 43] and relapsing polychondritis [44] haveall been made in small case series reviews.

Yellow nail syndrome

Yellow nail syndrome is a rare syndrome that was first described in 1964 by SAMMAN and WHITE

[45] and is characterised by bronchiectasis, lymphoedema and a characteristic appearance of thenails. The underlying pathological defect is not clear, although a recent study revealing anassociation with chronic rhinosinusitis suggests a possible defect in an inflammatory pathway or

mucociliary clearance rather than a structural defect within the lung itself [46].

Idiopathic bronchiectasis

In two large studies [47, 48], which identified the cause of bronchiectasis in adults, a significantproportion of patients (26% and 53%, respectively) were found to have no identifiable cause andwere labelled as having idiopathic bronchiectasis, the majority of whom were found to be femaleand nonsmokers. As all the patients studied had undergone rigorous clinical testing and theirhistory had been reported, leading to the exclusion of all known causes, including geneticdisorders, it is unlikely under recognition of known causes of bronchiectasis could have occurred.

Even in paediatric studies, with much shorter follow-up periods and clear exposure histories, nocause could be found for bronchiectasis in 25% of the patients [32]. It is clear, therefore, that thereis still much to learn about bronchiectasis and its underlying pathogenesis.

Statement of interest

None declared.

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13. Parr DG, Guest PG, Reynolds JH, et al. Prevalence and impact of bronchiectasis in a1-antitrypsin deficiency. Am J

Respir Crit Care Med 2007; 176: 1215–1212.

14. Cuvelier A, Muir JF, Hellot MF, et al. Distribution of a(1)-antitrypsin alleles in patients with bronchiectasis. Chest

2000; 117: 415–419.

15. Wilson R, Roberts D, Cole P. Effect of bacterial products on human ciliary function in vitro . Thorax 1985; 40: 125–131.

16. Hingley ST, Hastie AT, Kueppers F, et al. Effect of ciliostatic factors from Pseudomonas aeruginosa on rabbit

respiratory cilia. Infect Immun 1986; 51: 254–262.

17. Bayram H, Devalia JL, Sapsford RJ, et al. The effect of diesel exhaust particles on cell function and release of

inflammatory mediators from human bronchial epithelial cells in vitro . Am J Respir Cell Mol Biol 1998; 18: 441–448.

18. Walker TR, Kiefer JE. Ciliastatic components in the gas phase of cigarette smoke. Science 1966; 153: 1248–1250.

19. Fajac I, Viel M, Sublemontier S, et al. Could a defective epithelial sodium channel lead to bronchiectasis. Respir Res

2008; 9: 46.

20. Bienvenu T, Sermet-Gaudelus I, Burgel PR, et al. Cystic fibrosis transmembrane conductance regulator channel

dysfunction in non-cystic fibrosis bronchiectasis. Am J Respir Crit Care Med 2010; 181: 1078–1084.

21. Agarwal R. Allergic bronchopulmonary aspergillosis. Chest 2009; 135: 805–826.

22. Skov M, Poulsen LK, Koch C. Increased antigen-specific Th-2 response in allergic bronchopulmonary aspergillosis

(ABPA) in patients with cystic fibrosis. Pediatr Pulmonol 1999; 27: 74–79.23. Behera D, Guleria R, Jindal SK, et al. Allergic bronchopulmonary aspergillosis: a retrospective study of 35 cases.

Indian J Chest Dis Allied Sci 1994; 36: 173–179.

24. Chakrabarti A, Sethi S, Raman DS, et al. Eight-year study of allergic bronchopulmonary aspergillosis in an Indian

teaching hospital. Mycoses 2002; 45: 295–299.

25. Agarwal R, Gupta D, Aggarwal AN, et al. Clinical significance of hyperattenuating mucoid impaction in allergic

bronchopulmonary aspergillosis: an analysis of 155 patients. Chest 2007; 132: 1183–1190.

26. Cunningham-Rundles C, Bodian C. Common variable immunodeficiency: clinical and immunological features of

248 patients. Clin Immunol 1999; 92: 34–48.

27. Thickett KM, Kumararatne DS, Banerjee AK, et al. Common variable immune deficiency: respiratory

manifestations, pulmonary function and high-resolution CT scan findings. QJM 2002; 95: 655–662.

28. Conley ME, Howard V. Clinical findings leading to the diagnosis of X-linked agammaglobulinemia. J Pediatr 2002;

141: 566–571.29. Conley ME, Notarangelo LD, Etzioni A. Diagnostic criteria for primary immunodeficiencies. Representing PAGID

(Pan-American Group for Immunodeficiency) and ESID European Society for Immunodeficiencies. Clin Immunol

1999; 93: 190–197.

30. Vendrell M, de Gracia J, Rodrigo MJ, et al. Antibody production deficiency with normal IgG levels in

bronchiectasis of unknown etiology. Chest 2005; 127: 197–204.

31. Holmes AH, Pelton S, Steinbach S, et al. HIV related bronchiectasis. Thorax 1995; 50: 1227.

32. Li AM, Sonnappa S, Lex C, et al. Non-CF bronchiectasis: does knowing the aetiology lead to changes in

management? Eur Respir J 2005; 26: 8–14.

33. Glassroth J. Pulmonary disease due to nontuberculous mycobacteria. Chest 2008; 133: 243–251.

34. Reich JM, Johnson RE. Mycobacterium avium complex pulmonary disease presenting as an isolated lingular or

middle lobe pattern. The Lady Windermere syndrome. Chest 1992; 101: 1605–1609.

35. Camus P, Piard F, Ashcroft T, et al. The lung in inflammatory bowel disease. Medicine (Baltimore) 1993; 72: 151–183.36. Mahadeva R, Walsh G, Flower CD, et al. Clinical and radiological characteristics of lung disease in inflammatory

bowel disease. Eur Respir J 2000; 15: 41–48.

37. Despaux J, Manzoni P, Toussirot E, et al. Prospective study of the prevalence of bronchiectasis in rheumatoid

arthritis using high-resolution computed tomography. Rev Rhum Engl Ed 1998; 65: 453–461.

38. Hillarby MC, McMahon MJ, Grennan DM, et al. HLA associations in subjects with rheumatoid arthritis and

bronchiectasis but not with other pulmonary complications of rheumatoid disease. Br J Rheumatol 1993; 32: 794–797.

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39. Uffmann M, Kiener HP, Bankier AA, et al. Lung manifestation in asymptomatic patients with primary Sjogren

syndrome: assessment with high resolution CT and pulmonary function tests. J Thorac Imaging 2001; 16: 282–289.

40. Andonopoulos AP, Yarmenitis S, Georgiou P, et al. Bronchiectasis in systemic sclerosis. A study using high

resolution computed tomography. Clin Exp Rheumatol 2001; 19: 187–190.

41. Fenlon HM, Doran M, Sant SM, et al. High-resolution chest CT in systemic lupus erythematosus. AJR Am J

Roentgenol 1996; 166: 301–307.

42. Souza AS Jr, Muller NL, Marchiori E, et al. Pulmonary abnormalities in ankylosing spondylitis: inspiratory and

expiratory high-resolution CT findings in 17 patients. J Thorac Imaging 2004; 19: 259–263.

43. Casserly IP, Fenlon HM, Breatnach E, et al. Lung findings on high-resolution computed tomography in idiopathic

ankylosing spondylitis – correlation with clinical findings, pulmonary function testing and plain radiography. Br J

Rheumatol 1997; 36: 677–682.

44. Davis SD, Berkmen YM, King T. Peripheral bronchial involvement in relapsing polychondritis: demonstration by

thin-section CT. AJR Am J Roentgenol 1989; 153: 953–954.

45. Samman PD, White WF. The "Yellow Nail" syndrome. Br J Dermatol 1964; 76: 153–157.

46. Nisbet M, Deveraj A, Meister M, et al . Yellow nail syndrome and bronchiectasis. Am J Respir Crit Care Med 2009;

179: A3216. Available from: http://ajrccm.atsjournals.org/cgi/reprint/179/1_MeetingAbstracts/A3216.pdf.

47. Shoemark A, Ozerovitch L, Wilson R. Aetiology in adult patients with bronchiectasis. Respir Med 2007; 101: 1163–1170.

48. Pasteur MC, Helliwell SM, Houghton SJ, et al. An investigation into causative factors in patients with

bronchiectasis. Am J Respir Crit Care Med 2000; 162: 1277–1284.

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Chapter 2

Pulmonary defence

mechanisms and

inflammatory pathways

in bronchiectasisB.N. Lambrecht* ,# , K. Neyt* and C.H. GeurtsvanKessel* ,"

Summary

Over recent years there has been a tremendous increase in theunderstanding of pulmonary immunity, mostly driven by largeresearch efforts in understanding the basis of asthma andchronic obstructive pulmonary disease. Bronchiectasis is well

understood. In this article, an overview of pulmonary defencemechanisms as well as inflammatory mechanisms is given as abasis to understand the pathogenesis of bronchiectasis.

Keywords: Bronchiectasis, inflammatory mechanisms,immunity, pulmonary defence

*Dept of Pulmonary Medicine,Laboratory of Immunoregulation andMucosal Immunology, GhentUniversity, Ghent, Belgium.#Dept of Pulmonary Medicine, and"Dept of Virology, ErasmusUniversity Medical Center,Rotterdam, The Netherlands.

Correspondence: B.N. Lambrecht,Dept of Pulmonary Medicine,Laboratory of Immunoregulation andMucosal Immunology, GhentUniversity, De Pintelaan 185, B-9000Ghent, Belgium, [email protected]


B ronchiectasis is a chronic disorder characterised by permanent dilatation of the bronchiaccompanied by inflammatory changes in their walls and in the adjacent lung parenchyma.

The pathogenesis is related to recurrent inflammation of the bronchial walls combined withfibrosis in the surrounding parenchyma. The resultant traction on weakened walls leads toeventual irreversible dilatation [1]. Bronchiectasis can result from defective pulmonary defencemechanisms that lead to recurrent, severe and tissue-damaging microbial insults or chronicbacterial colonisation with persistent inflammation leading to structural changes to the airway wall. Given the fact that restoration of inflammation and return to immune homeostasis is crucial

in the lung to protect the delicate gas exchange machinery, it is also possible that bronchiectasisresults from defective anti-inflammatory pathways that serve to dampen chronic inflammation.Therefore, in this chapter we provide a brief overview of lung defence mechanisms and how theseimmune defence mechanisms can contribute to chronic inflammation and structural changes tothe airway wall if not properly counter-regulated by anti-inflammatory pathways. The majorinflammatory cell types found in bronchiectasis are neutrophils in the airway lumen causingpurulent sputum and macrophages, dendritic cells (DCs) and lymphocytes in the airway wall [2, 3].

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The latter cells often occur in lymphoid aggregates or so-called tertiary lymphoid follicles, and aretypically seen in patients with tubular bronchiectasis and are a major cause of small airway obstruction [4].

Mechanical and physical pulmonary defence mechanisms

The inspired air is contaminated with toxic gases, particulates and microbes. The first line of defence of the lung is made up of the complex physical shape of the conducting upper and lowerairways, causing a highly turbulent airflow that facilitates the impaction, sedimentation anddeposition of particulate matter and microorganisms on the mucosa, followed by the removal of these deposited particles by the mucociliairy blanket and/or the physical expulsion from therespiratory tract by sneezing, coughing or swallowing. Reductions in the cough reflex areassociated with increased frequency of respiratory infections, but it is not known at presentwhether this would also predispose to development of bronchiectasis [5]. The presence of isolatedmiddle lobe bronchiectasis and colonisation with nontuberculous mycobacteria (the so-calledLady Windermere syndrome) has been proposed to be caused by cough suppression [6].

The action of the mucociliary blanket is a dynamic and complexly regulated escalator for bringinginhaled particles to the throat so that they can be swallowed. Defects in the function of themucociliary blanket can cause bronchiectasis. The conducting airways are lined with ciliatedepithelium and the structure and function of the cilia in propulsing mucus has been extensively studied [7–9]. Genetic defects in the structure of the outer dynein arm proteins that connectmicrotubules in cilia are the cause of primary ciliary dyskinesia [10]. Other mutations involve the ktu gene, which is involved in the assembly of both the outer dynein and the inner dynein arm [11].Defects in radial spoke head proteins are associated with abnormalities of the central microtubule pairof the cilium (presence of only one microtubulus rather than two) [10]. Ciliary disturbances(sometimes associated with situs inversus; Kartagener syndrome) almost always lead to bronchiectasis

and are often also associated with chronic rhinosinusitis. The correct movement of cilia and functionof the mucociliary escalator also depend on the low viscosity of the periciliary fluid layer, physically ahydrated sol layer, allowing sufficient separation between the apical side of the epithelium and theviscous mucous blanket covering the cilia. If the periciliary fluid layer is concentrated (i.e. like in cysticfibrosis (CF)), the periciliary fluid layer becomes thinner and the cilia become entangled in the mucuslayer, thus impeding normal ciliary propulsion of the mucus [12, 13].

Humoral innate immune mechanisms in the lung

Innate immune defences are evolutionary conserved pathways of defence that kill microbes in a

generic pathway, often relying on the recognition and antagonism of common motifs in microbialproteins or lectins, the so-called pathogen-associated molecular patterns (PAMPs), which are socrucial for the function of the microbe that their antagonism leads to loss of pathogenicity. Justlike acquired or adaptive immunity, innate immunity consists of a humoral and a cellular part.

Humoral innate defence mechanisms are elaborate in the lung and consist of lactoferrin, lyzozyme,defensins, complement, cathelicidins and collectins [14]. These molecules can be produced by airway structural cells or by recruited innate immune cells such as neutrophils and macrophages(see later). Lactoferrin chelates Fe2+ molecules that are crucial for the growth of some bacteria butalso stimulates the function of neutrophils. Lyzozyme degrades Gram-positive cell walls. Defensins

are made by neutrophils (a-defensins) and epithelial cells (b-defensins). They serve to make poresin bacterial cell walls, and thus are truly antibacterial peptides but also neutralise viruses and fungiand recruit DCs via activation of the CCR6 chemokine receptor on these cells [15]. The properfunction of defensins depends on the correct salt concentration in the airway surface liquid [16].Thus, in CF patients defensin function against Staphylococcus aureus is defective, possibly explaining the susceptibility to colonisation, although this theory has also been questioned. LL37 isa well-known airway cathelicidin that is also salt sensitive and has broad antimicrobial activity but

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also has effects on innate and adaptive immune cells [17]. Surfactant protein A and D arecollectins that opsonise bacteria and viruses such as influenza. A closely related collectin family member is mannose binding lectin (MBL), it is not secreted into the lung lining fluid but is animportant circulating factor that can activate the complement cascade. Deficiency of MBL is acause of recurrent bacterial infections and could be a cause of bronchiectasis. Low MBL levels inCF patients and other forms of bronchiectasis are also associated with a more rapid decline in lungfunction [18].

Cellular innate immune mechanisms in the lung

The cellular arm of innate immunity in the lung is primarily made up of alveolar macrophages andrecruited neutrophils (fig. 1). Alveolar macrophages serve an important function in thephagocytosis, killing and/or neutralisation of inhaled particulate antigens. Resident alveolarmacrophages continuously encounter inhaled substances due to their exposed position in thealveolar lumen. These cells are packed with enzymes, metabolic products and cytokines that arevital to defence of the alveolar space but can potentially damage the alveolocapillary membrane.

To avoid collateral damage to type I and type II alveolar epithelial cells (AEC) in response toharmless antigens, they are kept in a quiescent state, producing few inflammatory cytokines [19].It has been estimated previously, that the pool of alveolar macrophages can handle up to 10 9

Stimulus

Secondaryneutrophil

influx

Activation ofdendritic cells

Direct triggeringof epithelial cells

Ingestion byalveolar

macrophages

TNF-α, IL-1,G-CSF, GM-CSF,chemokines (IL-8)

Figure 1. When a pathogen enters the lung, it triggers both epithelial cells, macrophages and dendritic cells.

The epithelial cells make chemokines that subsequently attract neutrophils that help in phacocytosing the

pathogens. All recruited cells together with epithelial cells then make cytokines and growth factors that further

enforce innate immune responses to the pathogen by further recruitment of inflammatory cells. TNF: tumournecrosis factor; IL: interleukin; G-CSF: granulocyte colony-stimulating factor; GM-CSF: granulocyte-macrophage

colony-stimulating factor.

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intratracheally injected bacteria before there is spill-over of bacteria to DCs and before adaptiveimmunity is induced [20]. Elegant studies have demonstrated that in vivo elimination of alveolarmacrophages using clodronate filled liposomes lead to overt inflammatory reactions to otherwiseharmless particulate and soluble antigens [21], but also to an increased sensitivity to bacterial,fungal and viral infection. In their exposed position, alveolar macrophages serve as the first line of defence against inhaled pathogens not only by directly acting as the main phagocytes, but also asan important producer of pro-inflammatory chemokines, cytokines and lipid mediators; bioactive

mediators that recruit other cell types to the lung.

In contrast to alveolar macrophages that reside in the lung and serve as an immediate line of innate defence against inhaled pathogens, neutrophils are recruited within minutes followinginoculation of microbes into the lung. The main function of neutrophils is phagocytosis andkilling of microbes, particularly fungi such as Aspergillus sp. and Pneumocystis jeroveci . They canalso kill microorganisms through the release of a-defensins and lyzozyme. Neutrophil killingfunction depends on oxidative enzymes such as those of the NADPH oxidase system andmyeloperoxidase. Chronic granulomatous disease is caused by missense, nonsense, frameshift,splice or deletion mutations in the genes for p22(phox), p40(phox), p47(phox), p67(phox)(autosomal chronic granulomatous disease) or gp91(phox) (X-linked chronic granulomatousdisease), which result in variable production of neutrophil-derived reactive oxygen species [22].Neutrophil extravasation is also a highly organised process requiring the rolling, arrest anddiapedesis of cells on the vessel wall. Defects in certain integrins, selectins or their activator cancause defective neutrophil recruitment and cause recurrent pulmonary infections [23]. Oncerecruited, neutrophils can also further enhance more neutrophil recruitment through productionof cytokines (interleukin (IL)-1, tumour necrosis factor (TNF)-a and IL-6) as well as throughrelease of calcium binding proteins of the S100 family (S100A8, A9 and A12) that act on the RAGE(receptor for advanced glycation end products) receptor.

Induction of innate immune responses in the lung The above mechanisms of innate defence act in a coordinated fashion. Although a single aspect of the innate defence system can be triggered directly through recognition of foreign PAMPs, theinnate defence mechanisms are often induced simultaneously via triggering of common receptorson both phagocytes (for cellular defences) and epithelial cells (for inducing the production of humoral innate defence mechanisms). The most famous pattern recognition receptors belong tothe family of Toll-like receptors (TLR)1-11, NOD-like receptors, RIG-I-like receptors and C-typelectin receptors [24]. These receptors recognise particular conserved PAMPs on specific groups of microbes. The archetypical TLR4 is expressed at the cell surface and recognises the Gram-negative

cell wall component lipopolysaccharide, whereas TLR2 recognises peptidoglycan and TLR5recognises bacterial flagellin. The endosomal TLR receptors TLR3 recognise double-stranded RNA,TLR7 and TLR8 single-stranded RNA and TLR9 unmethylated CpG motifs [24]. The exact cellularlocalisation and downstream signalling mechanisms of these pathways have been studiedextensively over the past few years and several clinical primary immunodeficiency syndromes havebeen brought back to deficiencies in one of the signalling intermediates of these pathways.Deficiency of IRAK4, a critical intermediary in TLR4 signalling causes recurrent bacterialinfections, particularly at a young age [25]. Deficiency of the C-type lectin receptor dectin-1 or thedownstream signalling intermediate molecule CARD9 causes immunodeficiency to candida andP. jeroveci , most probably due to reduced induction of T-helper cell (Th)17 responses [26].

Conversely, over activity of these signalling cascades, for example caused by small polymorphismsin or mutations of negative regulators of these pathways are associated with auto-immunity andoverzealous inflammatory pathways. As one example, polymorphisms in the ubiquitin editingenzyme TNF-a-induced protein 3 (TNFAIP3, also known as A20), cause hypersensitivity of TLR and cytokine receptors and are often found in patients with systemic lupus erythematosus [27].Our own unpublished data also show that genetic deficiency of A20 in epithelial cells causes severemucosal inflammation in response to inhalation of intrinsically harmless proteins, but it is

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unknown at present how this could be implicated in the regulation of inflammatory pathwaysrelevant to bronchiectasis.

Adaptive cellular immunity

Like innate immunity, adaptive or acquired immunity consists of a cellular and a humoral arm.Cellular adaptive immunity is made up of different types of T-lymphocytes, whereas humoralimmunity is made up of B-lymphocytes and plasma cells and their secreted product;immunoglobulins (Ig).

Induction of adaptive cellular immunity by DCs

DCs are potent antigen presenting cells that have emerged as key regulators of adaptive immunity (see [28] for a more detailed review on the biology of lung DC function). The general function of lung DCs is to recognise and pick up foreign antigens at the periphery of the body, andsubsequently migrate to the draining mediastinal lymph nodes where the antigen is processed into

immunogenic peptides and displayed on major histocompatibility complex (MHC)I and MHCIImolecules for presentation to naıve T-cells. In fact, these cells should be seen as specialised cells of the mononuclear phagocyte system, which have evolved from the cells of the innate immunesystem to control adaptive immunity that came later in evolution [29]. DCs express all the patternrecognitions receptors shared with phagocytes of the innate immune system, yet at the same timealso have the machinery to talk to T-cells and B-cells and relay information about the type of antigen to these cells, so that a tailor-made adaptive response is induced and long-term memory isinitiated. As these cells respond to many noxious stimuli from both the outside world (PAMPs)and from within (danger-associated molecular patterns) and at the same time closely communicate with lung structural cells such as alveolar epithelial cells, endothelial cells andfibroblasts, it has been proposed that they could be crucial players in many lung diseases,particularly where T-cell responses are involved in initiation of maintenance of the disease [30].Very recently the first case reports of patients presenting with defects in the DC system have beenreported. These DC-deficient patients are at risk of severe viral skin infections and pulmonary infections with atypical mycobacteria, which also leads to bronchiectasis [31, 32]. Our ownexperiments employing DC-deficient mice have elucidated a crucial role for these cells in theinduction of antiviral immunity to influenza virus, via induction of both CD4 and CD8 T-cellresponses [33]. Similar conclusions have been reached in models of tuberculosis and bacterial lunginfections [34]. Conversely, DCs are also heavily involved in maintaining immunopathology inwhich T-cells play a predominant role, the best example being the mucosal inflammation seen inasthma and chronic obstructive pulmonary disease (COPD) [35]. In humans with bronchiectasis,as well as in a rat model of bronchiectasis, there is an increased infiltration of the airway wall withDCs [2, 3]. The airways of patients with diffuse panbronchiolitis, a disorder of the smallbronchioles that can also lead to bronchiectasis, contain increased numbers of DCs that have aclearly activated phenotype, while treatment with neomacrolides reduces the antigen presentingcapacities of these DCs [36, 37].

Constituents of adaptive cellular immunity

Adaptive cellular immunity consists of defined subsets of CD4+ Th cells and CD8+ cytotoxic T-

cells. Once DCs transport their antigenic cargo to the draining lymph nodes, they induce theproliferation and differentiation of naıve T-cells into particular types of T-cell responses (fig. 2).Discrete types of Th cells provide crucial help for different parts of the innate and adaptiveimmune response [38]. Th1 cells make interferon (IFN)-c and mainly provide help to monocyticcells, including macrophages and DCs, thus enforcing killing of intracelullar pathogens, and at thesame time enforcing opsonisation of these through provision of B-cell help. Conversely, Th2 cellsmake IL-4, IL-5 and IL-13 providing help to eosinophils, mast cells and basophils to eliminate

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complex helminths, and at the sametime induce IgG1 and IgE from B-cells to arm the basophils and mastcells with effector potential. For along time since the original descrip-tion of the Th1/Th2 concept, it hasbeen unclear which subtype of T-

cell help was important for indu-cing neutrophilic responses andprotection from extracellular patho-gens such as fungi. This gap hasbeen breached recently by the dis-covery of the cytokines IL-17 andIL-22 which are produced by Th17cells that induce neutrophilic inflam-mation and production of defensinsby epithelial cells and are important

for clearance of fungi and extracel-lular bacteria [39].

The precise signals that inducedifferent types of Th lineage-com-mitment of naıve T-cells has beenintensely studied [38]. Antigen pre-senting cells can provide differentlevels and quality of signal one(peptide-MHC), signal two (co-stimulatory molecules) and signal

three (instructive cytokines) tonaıve T-lymphocytes upon antigenencounter and triggering of their

pattern recognition receptors [29]. When stimulated through the unique T-cell receptor (TCR),naıve CD4+ T-cells differentiate into Th1 cells in the presence of high amounts of IL-12. IL-12instructs Th1 development via activation of signal transducer and activator of transcription (STAT)4and the lineage instructing transcription factor T-bet. IL-17 producing cells are induced whenexposed to a cocktail of cytokines including transforming growth factor (TGF)-b, IL-6, and IL1a/b,while IL-23 further enhances the proliferation of these cells. The Th17 lineage specific transcriptionfactor RAR-related orphan receptor ct enforces Th17 characteristics in naıve T-cells, and is induced

by the cocktail of cytokines instructive to their development. The mechanisms leading to Th2 celldifferentiation in vivo are still poorly understood, but in most instances require a source of IL-4 toactivate the transcription factors STAT6 and GATA-3, and a source of IL-2, IL-7 or thymic stromallymphopoietin to activate the transcription factor STAT5 [40–44]. Despite the overwhelmingevidence that IL-4 is necessary for most Th2 responses, DCs were, however, never found to produceIL-4 and it was therefore assumed that Th2 responses would occur by default, in the absence of strong Th1 or Th17 instructive cytokines in the immunological DC T-cell synapse, or when thestrength of the MHCII-TCR interaction or the degree of co-stimulation offered to naıve T-cells wasweak [45–48]. In this model, naıve CD4 T-cells were the source of instructive IL-4. In an alternativeview, IL-4 is secreted by an accessory innate immune cell type, such as natural killer T-cells,

eosinophils, mast cells or basophils, that provide IL-4 in trans to activate the Th2-differentiationprogramme [49]. In the lung allergic response to house dust mite allergen, we have recently foundthat basophils help DCs to induce Th2 immunity by providing an important, but not essential sourceof IL-4 [50].

Lung DCs are also essential in instructing the selection and expansion of CD8 cytotoxic T-cellsthat recognise virus-infected cells, cells infected with intracellular bacteria and tumourally

IL-4

IL-10

IL-6

IL-1IL-23

IL-12

T-betSTAT4STAT1

Th2

Gata-3c-mafSTAT6

IL-4IL-5IL-13TNF-α

TGF-β

IFN- γ TNF-α

ROR γ STAT3

TGF-β

TGF-β

IL-10

IL-17IL-22

Treg

Anti-inflammatory

AllergyStimulates lgE, lgG1Stimulates eosinophilsAntihelminthic

Suppresses lymphocytesProfibrotic?

AntifungalStimulates neutrophilsAutoimmunity

Intracellular pathogensStimulates macrophages

Stimulates lgG2aDelayed hypersensitivity

Th17

Th1

Th0Foxp3

Figure 2. T-cell polarisation induced by dendritic cells (DCs) and

their secreted cytokines. When a T-helper cell (Th) type 0 encounters

antigen on a DC, it will be induced to differentiate into variousmutually exclusive cell fates. Each T-cell differentiation programme is

controlled by transcription factors such as Gata-3, forkhead box P3

(Foxp3), RAR-related orphan receptor gamma (RORc) or T-bet,which enforce Th cell lineage choice. Eventually Th cells emerge

that are specialised for performing various antimicrobial tasks.

IL: interleukin; Treg: T-regulatory cell; TGF: transforming growthfactor; TNF: tumour necrosis factor; IFN: interferon; Ig: immunoglo-

bulin; STAT: signal transducer and activator of transcription.

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transformed cells via presentation of endogenous cellular antigen on the MHCI complex [33]. Animportant conceptual point is that DCs do not have to be infected themselves to perform this task,but can phagocytose virally infected or transformed cells and use the process of cross-presentationto present the exogenous antigen into their MHCI loading machinery. Once activated by DCs andCD4 T-cell help, cytotoxic T-cells can lyse and kill infected cells in a process requiring granzymeand/or perforin, or kill target cells in a FasL- and/or TNF receptor-like apoptosis inducing ligand-dependent manner, causing apoptotic cell death in targets [51].

Several defects in adaptive immunity are associated with increased susceptibility to lung infectionand can be an important risk factor for later development of bronchiectasis. Defects in the IL-12/IFNcSTAT1 axis are a well-known risk factor for mycobacterial infections and invasiveSalmonellosis [52]. Defects in the IL-23//Th17 axis are associated with increased risk of fungalinfections and P. jeroveci infections [53]. Patients with sporadic or autosomal dominant forms of the hyper IgE syndrome (Job’s syndrome when associated with connective tissue abnormalities)have mutations in STAT3, and hence deficient differentiation of Th17 cells [54, 55]. These patientsare at risk for severe recurrent Staphyloccal infections, pneumatocoeles and mucocutaneouscandidiasis. In recessive forms of the hyper IgE syndrome, mutations in DOCK8 have been

described, and these patients are similarly at risk for recurrent sinopulmonary infection and havedefects in Th17 generation [56]. The few biopsy studies that have been performed inbronchiectasis have seen increased infiltration of the bronchial wall with CD4 and CD8 T-cells.The neutrophilic inflammation seen in CF and other forms of bronchiectasis is typically associatedwith the increased presence of Th17 cells [57]. In bronchiectasis associated with allergicbronchopulmonary aspergillosis, one has also observed increased numbers of Th2 cells, thusexplaining the association with sputum eosinophilia.

Humoral immune mechanisms in the lung

Humoral immunity plays a predominant role in protection from severe infections withencapsulated bacterial strains. Antibodies are well known for their neutralising effects onsecondary infections and this is the principle of most vaccinations against childhood infections.During a primary infection, however, antibodies, some of which have broad-spectrum specificity (so-called natural antibodies), also have the capacity to activate complement and opsonisebacterial cell walls and capsules, thus facilitating clearance of the pathogens. Antibodies of the IgAand IgG class are actively secreted into the airway lumen via the action of the polymeric Igreceptor. Airway luminal IgA is an important defence against viral entry. Maybe the mostprevalent cause of bronchiectasis is deficiencies in humoral immunity, such as common variableimmunodeficiency (CVID), a group of disorders characterised by low to absent Ig and various

degrees of T-lymphocyte abnormalities [18, 58]. CVID can be caused by mutations in the proteinsinvolved in T–B-cell communication such as ICOS, BAFF, TACI and APRIL [59, 60]. This is arapidly evolving field and it is only a matter of time before all these mutations can be diagnosed ona routine basis.

Organised lymphoid structures and bronchiectasis

The organised accumulation of lymphocytes in lymphoid organs serves to optimise bothhomeostatic immune surveillance, as well as chronic responses to pathogenic stimuli [61]. Duringembryonic development, circulating haemopoietic cells gather at predetermined sites throughoutthe body, where they are subsequently arranged in T- and B-cell specific areas, leading to theformation of secondary lymphoid organs, such as lymph nodes and spleen. In contrast, the body has a limited second set of selected sites that support neo-formation of organised lymphoidaggregates in adult life. However, these are only revealed at times of local, chronic inflammationwhen so-called tertiary lymphoid organs (TLO) appear. Just like in lymph nodes and spleen, areasof TLO are characterised by formation of specialised high endothelial venules and the organised

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production of chemokines leads to cellular organisation of T-cells and B-cells in discrete areas. Inhumans, TLO has been observed in the joint and lung of rheumatoid arthritis [62], around theairways of COPD patients [63] and in the thyroid [64]. Certain infectious diseases are alsoaccompanied by the formation of TLO. Influenza virus infection of the respiratory tract leads toformation of inducible bronchus-associated lymphoid tissue (iBALT) that supports T- and B-cellproliferation and productive Ig class switching in germinal centres [65, 66]. Tertiary lymphoidfollicles or iBALT is frequently seen in tubular bronchiectasis, and the close association with

bronchi might explain the obstruction of small bronchioles and airway obstruction that is oftenseen. This is certainly the case in rheumatoid arthritis-associated bronchiectasis, in whichbronchial obstruction is often caused by strongly enlarged TLOs that impinge on the lumen of theairway, an entity known as follicular bronchiolitis by pathologists and reflecting the presence of B-cell follicles inside TLO structures [62]. Formation of TLO could be the result of chroniccolonisation of bronchiectatic airways by microbes, and indeed it has been proposed that latentadenoviral infection is a cause of follicular bronchiectasis [4]. However, in one school of thought,TLO formation can also be seen as a source of self-specific autoantibodies and a reflection of anunderlying auto-immune component of the disease. In TLO associated with rheumatoid arthritis-bronchiectasis, one has indeed seen the production of pathogenic antibodies to citrullinated

proteins [62].

Anti-inflammatory pathways

With its large surface area, the lung is a portal of entry for many pathogens as inhaled air iscontaminated with infectious agents, toxic gases and (fine) particulate matter. At the same time,inhaled microbes and toxic substances can gain easy access to the bloodstream across the delicatealveolar–capillary membrane. Innate and adaptive immune defence of this vulnerable barrier is noteasy and needs to be tightly controlled as too much oedema, inflammation and cellularrecruitment will lead to thickening of the alveolar wall and will jeopardise the diffusion of oxygenvital to life. Considering the large surface area of the respiratory epithelium and the volume of airinspired on a daily basis it is remarkable that there is so little inflammation under normalconditions, suggesting the presence of regulatory mechanisms that act to protect the gas-exchangemechanism. Even following severe bacterial or viral infection, a return to homeostasis is the usualoutcome. Understanding the conditions by which lung immune homeostasis is regulated might becrucial to advance our insight into the pathogenesis of inflammatory lung diseases such asbronchiectasis. One type of cell that has received particular attention in suppressing immuneresponses in the lung is the alveolar macrophage. Alveolar macrophages adhere closely to AECs atthe alveolar wall and are separated by only 0.2–0.5 mm from interstitial DCs. In macrophage-depleted mice, the DCs have a clearly enhanced antigen presenting function [67]. When mixedwith DCs in vitro , alveolar macrophages suppress T-cell activation through the release of nitricoxide (mainly in rodents), prostaglandins, IL-10 and TGF-b. Alveolar macrophages also expressCD200R, an inhibitory receptor that regulates the strength of innate immunity to inhaledpathogens. Another cell type that has received a lot of attention is the regulatory T-cell (Treg).Natural Tregs express high levels of CD25 and express the lineage specific transcription factorFoxp3 [68]. These cells are generated in the thymus and have a natural reactivity for self antigensas well as some foreign antigens, and mainly suppress autoimmunity [69]. Induced Tregs aregenerated when DCs encounter self antigen in the periphery or upon chronic immune stimulation.It is assumed that these induced Tregs serve to dampen overt immune activation to stimuli thatcannot be fully eliminated, a typical example being chronic helminth infections or mycobacterialinfections [70]. As bronchiectasis is a disorder of chronic inflammation accompanied by microbialcolonisation, it is very likely that increased Tregs are found inside lesions, although this has notbeen formally addressed. It is also possible that failure of Treg function at a certain stage of thedisease contributes to ongoing inflammation, which might ultimately progress to fibrosis. In thisregard it is a striking observation that Tregs also make TGF-b as part of their suppressiveprogramme. TGF-b might be at the crossroads of immunoregulation and fibrosis initiation.

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Immune regulation might also stem from changes in stromal cells of the airways, such as epithelialcells. Airway epithelial cells play a predominant role in deciding whether or not an acute orchronic stimulus like endotoxin is recognised or not [71]. Epithelial cells express many patternrecognition receptors and the sensitivity of these can be regulated through negative regulators of signalling. Finally, some epithelial derived cytokines, such as IL-37, have an intrinsically anti-inflammatory effect on innate immunity in the lung [72]. It is currently unknown if defects inthese counter-regulatory mechanisms are involved in the maintenance of inflammation in patients

with bronchiectasis.

Conclusion

There has been great progress in our knowledge of innate and adaptive immune responses in thelung. Immune defects in innate and adaptive cellular and humoral immunity can all lead tobronchiectasis. In contrast to other obstructive airway diseases, such as asthma and COPD, wehave not yet fully grasped the immunopathogenesis of chronic inflammation in this disorder.

Support statementB.N. Lambrecht is supported by grants from Fonds voor Wetenschappelijk Onderzoek Flanders(Odysseus Program), European Research Council (ERC) starting grant and Multidisciplinary Research Platform (GROUP-ID consortium) of University of Ghent, Ghent, Belgium. K. Neyt issupported by a fellowship of FWO Flanders.


None declared.

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Chapter 3

Histopathology of

bronchiectasisM. Goddard

Summary

The clinical presentation of bronchiectasis occurs after initial

irreversible damage to the airway has occurred. The clinician thenhas to control symptoms and limit the progression of the disease.A clearer understanding of the pathogenesis of this disease willenable the development of better treatment strategies.

Bronchiectasis is a multi-factorial disease process in whichthere are a number of key steps, although they are not alwaysclinically identifiable. There is often an initiator or damaging event such as a viral infection which, in an individual with apredisposing risk such as a degree of immune dysfunction or an

impaired mucociliary clearance system, leads to persistentand damaging bacterial infections. These infections go on toprovoke an inappropriate and self-damaging inflammatory response in which neutrophil activity leads to progressive tissuedamage and a relentless cycle of infection, inflammation andbronchial wall injury. Persistent infection and chronic inflam-matory cell infiltration further amplify the local inflammatory milieu and may lead to systemic complications.

Keywords: Aetiology, bronchiectasis, histopathology,

inflammation, neutrophils, pathogenesis

Correspondence: M. Goddard, Deptof Pathology, Papworh Hospital NHS

Foundation Trust, Papworth Everard,Cambridge, CB23 3RE, UK, [email protected]

Eur Respir Mon 2011. 52, 22–31.Printed in UK – all rights reserved.Copyright ERS 2011.

European Respiratory Monograph;ISSN: 1025-448x.DOI: 10.1183/1025448x.10003310

B ronchiectasis was first described at the beginning of the 19th century by LAENNEC [1]. Heascribed the term to the pooling of secretions in the airways leading to wall weakening and

dilatation. Whilst the term is often used loosely by radiologists to describe any airway dilatation,pathologically the term is used to describe an irreversible dilatation of the airway often associatedwith chronic suppuration.

Aetiology and classificationAetiologically, bronchiectasis may be divided into obstructive and nonobstructive types (table 1).

In the obstructive type of bronchiectasis airway dilation may develop from obstruction due to any cause. The disease is confined to the airways distal to the obstruction. Causes of obstruction may be luminal, such as the inhalation of foreign bodies. This is most common in children and shows a

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predilection for the right lower lobe and posteriorsegment of the right upper lobe [2–5]. The risk of developing bronchiectasis following foreign body inhalation has been assessed as 3–16% [6]. However,other causes of obstruction include mucus inspis-sation in allergic bronchopulmonary aspergillosis(ABPA) [7], with central or upper lobe bronchiec-

tasis, and distal to broncholitis. Tumours may alsocause obstruction and bronchiectasis but this is moreprevalent in the slower growing often polypoid tu-mours, such as carcinoid tumours, endobronchiallipomas and chondromas [8]. Extrinsic compressionof the bronchus may also lead to obstruction, andtypically hilar tuberculous lymphadenopathy canlead to bronchiectasis, particularly of the rightmiddle and lower lobes. The middle lobe, becauseof its relatively narrow lumen, is at particular risk of

compression or obstruction, a condition sometimesreferred to as middle lobe syndrome [9].

The pathogenesis of obstructive bronchiectasis isrelatively straightforward, as bronchial secretions ac-cumulate distal to the obstruction and becomeinfected producing inflammation and damage tothe bronchial wall which becomes weakened anddilated. This was recognised by LAENNEC [1].

There have been several attempts to classify non-

obstructive bronchiectasis, which are variably basedon a mixture of historic bronchographic and, morerecently, high-resolution computed tomography (HRCT), appearances (saccular or cystic,fusiform or cylindric) [10] and histological appearances (follicular) with lymphoid follicles inthe wall, as defined by WHITWELL [11]. Nonobstructive bronchiectasis is typically more wide-spread, affecting more than one lobe and most commonly affecting the basal segments of the lowerlobes [11–13]. The left lung is more frequently affected than the right and the disease processtypically involves the middle-order bronchi (fourth to ninth generations).

This classification is now probably unsatisfactory and of little pathological significance; although

the distribution of changes may provide a clue to the underlying aetiology. Post-infectivebronchiectasis is traditionally the most common underlying cause, is most often basal and may be confined to a single lobe. However, nonobstructive bronchiectasis may occur in associationwith a number of other conditions. In diseases where mucociliary clearance is impaired,bronchiectasis frequently, if not inevitably, develops. In cystic fibrosis [14] and ciliary dysmotility syndromes, such as primary ciliary dyskinesia arising from a defect in the dyneinarms [15], bronchiectais is more widespread, sometimes with upper lobe predominance. Theassociation of bronchiectasis with disturbances in mucociliary clearance mechanisms highlightsthe importance of local defence mechanisms within the airways in aetiological terms and interms of the pathogenesis of the disease. There may be primary defects in the immune systemwith abnormalities of neutrophil function, hypogammaglobulinaemia [16], immunoglobulin(Ig)A and IgG sub-class deficiencies [17], and in ataxia telangiectasia. Bronchiectasis may also beassociated with some autoimmune conditions including ulcerative colitis [18], rheumatoiddisease [19], Sjogren’s syndrome [20] and ankylosing spondylitis. Bronchiectasis is also as-sociated with several noninflammatory conditions within the lung, such as a1-antitrypsindeficiency, and is reported in some cases of pulmonary fibrosis but in these cases may be due totraction effects of the surrounding fibrosis.

Table 1. Causes of bronchiectasis

Bronchial obstruction

Foreign bodies

TumoursCarcinoid tumours

Endobronchial chondromas and lipomas

Mucous plugs

ABPA Nonobstructive

Post-infective

Measles Adenovirus

Pertussis

TuberculosisMucociliary abnormalities

Cystic fibrosis

Ciliary dysmotility syndromesPrimary ciliary dyskinesia

Immunological abnormalities

Hypogammaglobulinaemia IgA and IgGsub-class deficiencies

Neutrophil function abnormalities

Ataxia telangiectasia

Associated with systemic diseasesRheumatoid arthritis

Sjogren’s syndrome

Ankylosing spondylitisa1-antitrypsin deficiencyPulmonary fibrosis

ABPA: allergic bronchopulmonary aspergillosis;

Ig: immunoglobulin.

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Of the known causes or associations of bronchiectasis, childhood infection is probably the mostcommon accounting for up to 30% of cases, with immunodeficiencies present in up to 18%.However, in some studies, no underlying abnormality can be detected in .50% of cases.

Histopathological appearances

Histopathologically, bronchiectatic airways appear dilated and on examination have a cross-sectional area that is much larger than the accompanying pulmonary artery (fig. 1). The airway lumen is often filled with a mucopurulent exudate with neutrophils and macrophages (figs 2 and 3).The respiratory epithelium lining shows variable changes from a reserve cell hyperplasia tosquamous metaplasia (fig. 4) with active inflammation shown by epithelial and mucosal infiltrationby neutrophils and in severe exacerbations, ulceration (figs 5 and 6). The bronchial wall is oftendestroyed due to loss of fibromuscular tissues and the elastic framework, and may show erosion andloss of cartilage [21]. There is usually a reduction in submucosal glands. The wall may be thin but ismore often greatly thickened with extensive peribronchial fibrosis extending into the adjacent lungparenchyma (fig. 7) [22]. There is an associated chronic inflammatory cell infiltrate within the wall,predominantly lymphocytes and plasma cells, and in some cases lymphoid follicles with germinalcentres may be prominent [23]. The presence of B-cell immune activation through the presence of germinal centres and plasma cells in the walls of bronchiectatic airways, would support the role of antibodies in the immune response to persistent infection. However, bronchiectasis is associatedwith some autoimmune connective tissue diseases, in particular rheumatoid arthritis [19, 24, 25],and a role for autoimmunity in the destruction of the airway has also been suggested.

Eosinophils may be seen as part of the infiltrate as with any chronicairways inflammation. Whilst non-specific, they raise the possibility of

an associated fungal infection suchas Aspergillus . Although eosinophilsare commonly seen in the mucusplugs of ABPA, their presencewithin the airway wall inflamma-tion is nonspecific. Granulomas andmultinucleate giant cells may beseen in the wall and might be areaction to the inspissated luminalmaterial but the possibility of con-

comitant fungal or mycobacterialinfection should always be consid-ered. In established bronchiectasis,the histological pattern of chronicinflammation within the airway wallwith superimposed active inflam-mation, most likely reacting toconcomitant infection, has a fairly uniform appearance and provideslittle insight into the underlying

aetiology or pathogenesis.

The surrounding lung parenchymamay show a number of changes.Where there is distal luminal obli-teration of bronchi and bronch-ioles, the lung parenchyma may

Figure 1. Low-power view of a bronchiectatic airway; note the

airway lumen is much larger than that of the accompanyingpulmonary artery. Magnification64.

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show atelectasis due to absorptionand collapse. Obliterative changes insmall airways are important in con-tributing to airflow obstruction inbronchiectasis [10, 11]. Destructiveinflammation may lead to the for-mation of an abscess cavity, although

this may be difficult to distinguishfrom a distended, ulcerated airway.There may be accompanying inter-stitial pneumonitis, particularly incases of follicular bronchiectasis, andalso changes of an organising pneu-monia. Small airway changes, suchas bronchiolectasis, may be seen aspart of the whole disease process ormay be part of an underlying disease

leading to more proximal dilata-tion, as has been seen with smallairways disease, such as bronchiolitis[18, 26].

The airways are supplied by thebronchial arteries and the inflamma-tory destruction and healing processesresult in the formation of broncho-pulmonary anastamoses, probably dueto a mixture of new vessel formationand the re-opening of pre-existing,pre-capillary bronchopulmonary con-nections (fig. 8). Ulceration of the air-ways can lead to severe haemorrhageand haemoptysis. The formation of anastamoses and the loss of some of the alveolar capillary bed leads to thedevelopment of pulmonary hyperten-sion [27].

Focal proliferations of neuroendocrinecells are also seen and may lead tothe formation of multiple tumourlets,small aggregates of neuroendocrinecells in the walls of small airways.These are not specific to bronchiecta-sis and may be seen in a number of chronic lung conditions [28].

It has also been recognised that thepersistent chronic activation of the im-mune system in the wall of the air-way may lead to the development of bronchus-associated lymphoid tissue(BALT), especially in bronchiectasisassociated with Sjogren’s syndrome[29]. Increased incidence of BALTomas,

Figure 2. Bronchiectatic airway wall with dense chronic

inflammatory cell infiltrate, which includes lymphocytes, plasma

cells and eosinophils. Magnification620.

Figure 3. Bronchiectatic airway wall with luminal pus, neutrophilinfiltration of the airway epithelium and a dense chronic

inflammatory cell infiltrate. Magnification640.

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low-grade, B-cell lymphomas, is as-sociated with Sjogren’s syndromebut not specifically related to bron-chiectasis [20].

In chronic disease, further complica-tions may arise. Locally, the lung

may develop abscesses and even em-pyema, although this is less commonas the pleural space is often oblite-rated by fibrous adhesions. Bronchi-ectatic spaces may become colonisedby saprophytic fungi, most commonly Aspergillus sp.

Systemic dissemination of infectionmay lead to abscesses in other organs,notably the brain, and chronic sup-

puration may be complicated by systemic amyloidosis (type AA). Theincidence in bronchiectasis is unclearbut in one study of patients withsystemic amyloidosis requiring hae-modialysis, 40% had underlying bron-chiectasis [30].

Pathogenesis

The pathogenesis of bronchiectasisis complex and a number of different mechanisms contribute to the development of a similarmorphological appearance and different factors act together to set up a cycle of inflammation anddestruction that leads to damage and destruction of the bronchial wall [31].

The initiator to this sequence is usually damage to the bronchial epithelium. This may be due to anexternal insult or to an intrinsic deficiency within the patient. The most common predisposingfactor to the development of bronchiectasis is a severe childhood respiratory infection, which may be viral, such as measles or adenovirus, or bacterial, such as Bordetella pertussis [32–34]. The

resultant permanent dilatation of

the airways is thought to be duenot only to inflammation and des-truction of the bronchial wall butalso, in part, to a traction effectproduced by collapse of the sur-rounding lung parenchyma. How-ever, the persistence of infectionand inflammation are of paramountimportance in the progression of thedisease.

Whilst an underlying cause is notestablished in all cases, the numberand type of associations for bronch-iectasis gives us some indicationof what the important underlyingpathogenetic mechanisms may be.

Figure 4. Squamous metaplasia of the epithelium lining in

bronchiectasis. Magnification640.

Figure 5. Severely inflamed ulcerated bronchiectatic airway withno epithelium and surface granulation tissue. Magnification620.

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In post-infectious causes, the initi-ating viral infection appears to betransitory and, in the case of adeno-viruises, it has not been possible todemonstrate the persistence of thevirus within bronchiectasis by in situ hybridisation [35]. However, some

respiratory viruses have been shownto lead to abnormalities in ciliary function, which may persist for severalweeks [36].

Clinically, it is the recurrence andpersistence of bacterial infectionsin the airways with which mostpatients present that are of mostimportance and are linked to the

progression of the disease. There is aprevailing view that bacterial infec-tion in the lower respiratory tractprovokes an exaggerated and uncon-trolled neutrophilic response and that the complex interplay between bacterial infection and airway inflammation, along with the release of tissue damaging substances, leads to the progressive damagewhich typifies bronchiectasis.

In the early stages of bronchiectasis, the most common bacterial isolate is Haemophilus influenzae ,which has the capacity to directly damage the airway epithelium and induce the production of inflammatory mediators [37]. The typical immune response to H. influenzae is a T-helper (Th)1

response. However, some bronchiectasis patients with persistent infection have been found to havea Th2 response with a cytokine profile of interleukin (IL)-4 and IL-10. The release of cytokinescontributes to the inflammatory response within the airway and at the same time may also resultin a failure of the response to satisfactorily remove the organism [38].

Over time, a number of other or-ganisms have been found to beestablished within the airways, par-ticularly Streptococcus pneumoniae and Pseudomonas aeruginosa . The

initial damage to the epitheliumlining allows this secondary bacter-ial colonisation to occur, which fur-ther inhibits ciliary clearance andpromotes the persistence of infec-tion and damaging inflammation[39]. The importance of this persis-tence in bacterial colonisation may be related to the production of heat-labile products by the bacteria,which further damage ciliated cellsand inhibit ciliary activity. P. aeru-ginosa can be a particular problemas it is protected from cellular andhumoral attack because it survivesin a biofilm on the mucosal surface[40]. Pseudomonas has been shown

Figure 6. Ulcerated airway with surrounding fibrosis of the wall.

Magnification610.

Figure 7. A bronchiectatic airway showing an attenuated inflamedepithelium with surrounding inflammation and fibrosis extending into

the peribronchial lung parenchyma. Magnification620.

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to produce phenazine pigments thatcan inhibit ciliary action through amechanism which leads to a reduc-tion in cellular cAMP and ATP.Furthermore, pseudomonal pyocya-nin can lead to epithelial disruptionand rhamnolipids have a ciliostatic

effect [41, 42]. Alveolar macropha-ges are an important mediator of defence against Pseudomonas andstimulated macrophages secrete cyto-kines that both recruit and activateneutrophils, thus potentially amplify-ing both the inflammatory responseand the potential for further tissuedamage [43, 44].

The resultant inflammatory reactionis an important pathogenic mechan-ism in the weakening of the bron-chial wall. Much of the damage

appears to relate to the release of proteolytic enzymes and oxygen free radicals from neutrophils.The severity of an inflammatory response is dependent on the interplay of several cytokines, whichmay be both pro- and anti-inflammatory [45]. In a well-regulated system, the inflammatory cascade is proportionate to the triggering bacterial stimulation and is switched off. There isevidence that in bronchiectasis the inflammatory response is disproportionate to the infectiveburden and that the inflammatory response persists [43, 46]. Indeed, in the early phases of bronchiectasis, active airway inflammation has even been reported in the absence of identi-fiable microbial infection, suggesting a dysregulation of the cytokine network independent of infection [47].

Neutrophils are potent effectors in inflammatory responses and secrete anti-microbial substances,as well as reactive oxygen free radicals [48]. Bronchoalveolar lavage (BAL) studies have de-monstrated that neutrophils are consistently present in patients with bronchiectasis, even whensterile and clinically stable, but increase in the presence of potential pathogens [49, 50].Recruitment and migration of neutrophils in airways is facilitated by the activation of neutrophilsand the upregulation of adhesion molecules on endothelial cells [51–53]. These changes areregulated by cytokines, particularly IL-1 and tumour necrosis factor (TNF)-a, as well as

lipopolysaccharide (LPS), which have been shown to be increased in the airways of patients withbronchiectasis [54, 55]. Activated neutrophils secrete potentially tissue damaging enzymes such asneutrophil elastase, proteinase 3 and metalloproteinases. Levels of these enzymes in BAL sampleshave been shown to correlate with neutrophil numbers and markers of disease activity such as 24-hour sputum production [56]. These enzymes can directly damage the structural integrity of theairway via damage to the basement membrane and elastin framework [57–60]. Neutrophils arealso an important source of oxygen free radicals. Release of oxygen free radicals are an importantpart of the defence against infection and are regulated by a protective anti-oxidant system.However, the excessive release of these oxidants can overwhelm the defence mechanisms and causetissue damage via lipid peroxidation. Furthermore, reactive oxygen species may amplify the

inflammatory response through the induction of cytokine and chemokine production by thestimulation of genes regulated by nuclear factor-kB. Studies in bronchiectatic patients have shownincreased levels of exhaled H2O2 correlating with neutrophil counts and disease activity [61, 62].

Macrophages also play a role in the disease progression as they secrete TNF-a, which promotesneutrophil recruitment, as well as other inflammatory mediators including IL-8, monocytechemotactic protein-1 and chemokines [23, 63]. Lymphocytes are also typically present in

Figure 8. Thick-walled bronchial artery in a bronchiecatic airway

wall. Magnification620.

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bronchial biopsies within the lamina propria and may also infiltrate the overlying epithelium.Studies assessing the relative proportions of CD4+ and CD8+ have produced mixed and, at times,conflicting results. Nonetheless, their presence indicates a cell-mediated immune responsecontributing to the overall inflammatory process [22].

Whilst the epithelial layer may be seen as a protective barrier through mucociliary clearance andgeneration of anti-bacterial substances, it also contributes to the inflammatory process through the

direct generation of pro-inflammatory cytokines [64]. Exposure to LPS leads to the generation of IL-8 and TNF-a which, as stated previously, are important in neutrophil recruitment. Bronchialepithelial cells are also able to upregulate surface adhesion molecules, such as intracellularadhesion molecule-1, aiding the migration of neutrophils [65, 66].

Thus, a number of pathways lead to the activation and recruitment of neutrophils into the airwayswhich, if not adequately regulated and controlled, results in the destruction of local tissue and thepersistence and progression of bronchiectasis. Individual variability in this innate response may help to explain why not all individuals exposed to predisposing triggers will go on to developbronchiectasis and offers potential targets for therapeutic intervention.


None declared.

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Care Med 1996; 153: 650–655.

18. Butland RJ, Cole P, Citron KM, et al. Chronic bronchial suppuration and inflammatory bowel disease. Q J Med

1981; 50: 63–75.19. Tahanami I, Imamuma T, Yamamoto Y, et al. Bronchiectasis complicating rheumatoid arthritis. Respir Med 1995;

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29. Yousem SA, Colby TV, Carrington CB. Follicular bronchitis/bronchiolitis. Hum Pathol 1985; 16: 700–706.

30. Akcay S, Akman B, Ozdemir H, et al. Bronchiectasis related amyloidosis as a cause of chronic renal failure.

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39. Wilson R, Dowlin RB, Jackson AD. The biology of bacterial colonisation and invasion of the respiratory mucosa.

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40. Mathee K, Ciofu O, Sternberg C, et al. Mucoid conversion of Pseudomonas aeruginosa by hydrogen peroxide:

a mechanism for virulence activation in the cystic fibrosis lung. Microbiology 1999; 145: 1349–1357.

41. Lau GW, Hasset DJ, Ran H. The role of pyocyanin in Pseudomonas aeruginosa infection. Trends Mol Med 2004; 10:

599–606.

42. Caldwell C, Chen Y, Goetzmann HS, et al. Pseudomonas aeruginosa exotoxin pyocyanin causes cystic fibrosisairway pathogenesis. Am J Pathol 2009; 175: 2473–2488.

43. Chmiel JF, Davis PB. State of the art: why do the lungs of patients with cystic fibrosis become infected and why

can’t they clear infection? Respir Res 2003; 4: 8.

44. Lu W, Hisatsume A, Koga T, et al. Cutting edge: enhanced pulmonary clearance of Pseudomonas aeruginosa by

Muc1 knockout mice. J Immunol 2006; 176: 3890–3894.

45. Wouters EFM. Local and systemic inflammation in chronic obstructive pulmonary disease. Proc Am Thorac Soc

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46. Aldallal N, Mc Naughton EE, Manzel LJ, et al. Inflammatory response in airway epithelial cells isolated from

patients with cystic fibrosis. Am J Respir Crit Care Med 2002; 166: 1248–1256.

47. Angrill J, Agusti C, De Celis R, et al. Bronchial inflammation and colonisation in patients with clinically stable


48. Liu Y, Shaw Sk, Ma S, et al . Regulation of leucocyte transmigration: cell surface interactions and signalling events. J Immunol 2004; 172: 7–13.

49. Eller J, Lap e Silva JR, Poulter LW, et al. Cells and cytokines in chronic bronchial infection. Ann NY Acad Sci 1994;

725: 331–345.

50. Loukides S, Bouros D, Papatjheodorou G, et al. Exhaled H2O2 in steady-state bronchiectasis: relationship with

cellular composition in induced sputum, spirometry, and extent and severity of disease. Chest 2002; 121: 81–87.

51. Adams DH, Shaw S. Leucocyte-endothelial interactions and regulation of leucocyte migration. Lancet 1994; 343:

831–836.

52. Hogg JC. Leukocyte traffic in the lung. Ann Rev Physiol 1995; 57: 97–114.

53. Zheng L, Tipoe G, Lam WK, et al. Upregulation of circulating adhesion molecules in bronchiectasis. Eur Respir J

2000; 16: 691–696.

54. Carlos T, Kovach N, Schwarz B, et al. Human monocytes bind to two cytokine induced adhesive ligands on

cultured human endothelial cells: endothelial-leukocyte adhesion molecule-1 and vascular cell adhesionmolecule-1. Blood 1991; 77: 2266–2271.

55. Dustin ML, Rothlein R, Bhan AF, et al . Induction by IL-1 and interferon-c: tissue distribution, biochemistry and

function of a nature adherence molecule (ICAM-1). J Immunol 1986; 137: 245–254.

56. Pang JA, Cheng A, Chan HS, et al. The bacteriology of bronchiectasis in Hong Kong investigated by protected

catheter brush and bronchoalveolar lavage. Ann Rev Respir Dis 1988; 139: 14–17.

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57. Sepper R, Kontinnen YT, Ding Y, et al. Human neutrophil collagenase (MMP-8) identified in bronchiectasis BAL

fluid, correlates with severity of disease. Chest 1995; 107: 1641–1647.

58. Zheng L, Lam WK, Tipoe GL, et al. Overexpression of matrix metalloproteinases-8 and -9 in bronchiectasis

airways in vivo . Eur Respir J 2002; 20: 170–176.

59. Sepper R, Kontinnen YT, Sorsa T, et al. Gelatinolytic and type-IV collagenolytic activity in bronchiectasis. Chest

1994; 106: 1129–1133.

60. Doring G. The role of neutrophil elastase in chronic inflammation. Am J Respir Crit Care Med 1994; 150:

S114–S117.

61. Lloberes P, Monserrat E, Monserrat JM, et al. Sputum sol phase proteins and elastase activity in patients with

clinically stable bronchiectasis. Thorax 1992; 47: 88–92.

62. Loukides S, Horvath I, Wodehouse T, et al. Elevated levels of expired breath hydrogen peroxide in bronchiectasis.

Am J Respir Crit Care Med 1998; 158: 991–994.

63. Simpson JI, Grissell TV, Gibson PG. Innate immune activation in bronchiectasis. Eur Respir J 2004; 24: Suppl. 48,

210S.

64. Devalia JL, Davies RJ. Airway epithelial cells and mediators of inflammation. Respir Med 1993; 87: 405–408.

65. Look DC, Rapp SR, Keller BT, et al. Selective induction of intercellular adhesion molecule-1 by interferon-c in

airway epithelial cells. Am J Physiol 1992; 263: L79–L87.

66. Humlicek AL, Pang L, Look DC. Modulation of airway inflammation and clearance by epithelial ICAM-1. Am J

Physiol Lung Cell Mol Physiol 2004; 287: L598–L607.

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Chapter 4

Assessment and

investigation of adults

with bronchiectasisM. Drain and J.S. Elborn

Summary The diagnosis of bronchiectasis is made on the basis of high-resolution computed tomography (HRCT) scan findings. Adiagnosis of bronchiectasis should be considered in allpatients with persistent cough productive of sputum, whereanother clear diagnosis has not been made. This includespatients with an initial diagnosis of chronic obstructivepulmonary disease or severe asthma. Once bronchiectasis

has been confirmed by HRCT scanning, patients shouldundergo a range of investigations to determine whether or notthere is an underlying cause. This can usually be determinedin approximately 50% of patients with bronchiectasis. Thecommon conditions which should be sought are cysticfibrosis, immunodeficiency syndromes, primary ciliary dyski-nesia, and autoimmune diseases, such as rheumatoid arthritisand ulcerative colitis. For many of these conditions, there isspecific treatment to improve symptoms and reduce lung injury but, without an accurate diagnosis, appropriate therapy may not be instituted.

Keywords: Bronchiectasis, computed tomography scan, cysticfibrosis, primary ciliary dyskinesia, primary immunodeficiency

Centre for Infection and Immunity,School of Medicine, Dentistry andBiomedical Sciences, Queen’sUniversity Belfast, Belfast, UK.

Correspondence: J.S. Elborn, Centrefor Infection and Immunity, Schoolof Medicine, Dentistry andBiomedical Sciences, Queen’sUniversity Belfast, 97 Lisburn Road,Belfast, BT9 7BL, UK, [email protected]


B ronchiectasis is a generic diagnostic term that describes the pathological dilation of the airwaysfound in a number of chronic lung conditions. The aetiology of bronchiectasis is varied

(table 1), and, in most series, an underlying cause can only be definitively identified in 50% of cases [1, 2]. The importance of determining a cause lies in facilitating treatment that may improvesymptoms, reduce exacerbations and alter the course of the disease by preserving lung function. Inone series in children, extensive investigation detected a specific cause in 74% of thoseinvestigated, and this led to a change in treatment in 56% [3]. In an adult series from the samegeographical area, a diagnosis was again reached in 74%, and the treatment of 37% of these wasaffected by knowledge of the diagnosis [4].

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Childhood respiratory infection, e.g. whooping cough, measles, tuberculosis (TB) or severebacterial pneumonia, is cited as being responsible for a large proportion of cases of bronchiectasis,i.e. up to 50% [4–6]. This potential cause, however, is subject to recall bias, particularly since the

majority of cases present in the fifth and sixth decades of life. Many people of this age have hadmeasles, whooping cough or other childhood infections associated with respiratory infection,including pneumonia. In addition, the first episode of pulmonary infection could represent thefirst exacerbation of bronchiectasis. Bronchiectasis is found in association with numerousmultisystemic diseases, such as cystic fibrosis (CF) [7], immunodeficiencies [8], a1-antitrypsin(a1-AT) deficiency [9], primary ciliary dyskinesia (PCD) [10], rheumatoid arthritis andinflammatory bowel diseases, especially ulcerative colitis [1, 7, 11].

Prevalence

The prevalence of bronchiectasis is almost certainly underestimated. This is because it is acondition that many healthcare practitioners are unfamiliar with, and it is frequently mis-diagnosed as asthma or chronic obstructive pulmonary disease (COPD) due to the similarities inclinical findings (table 2).

In the USA, the prevalence of bronchiectasis has been estimated at 4.2 per 100,000 populationamong those aged 18–34 years, rising to 272 per 100,000 population in those aged .75 years [12].

Table 1. Causes of bronchiectasis in adults

Congenital Acquired

Cystic fibrosis#

Primary ciliary dyskinesia#

a1-Antitrypsin deficiency

Congenital anatomical defects

Tracheo-oesophageal fistulaBronchotracheomalacia

Tracheomegaly

Pulmonary sequestration

Yellow nail syndromeMarfan’s syndrome

Cystic fibrosis#

Primary ciliary dyskinesia#

Following infection#

Bacterial#

Whooping cough

Tuberculosis

Nontuberculous mycobacteria Viral

Measles

HIV #

Fungal ABPA #

Immunodeficiency

PrimaryCommon variable immunodeficiency#

X-linked agammaglobulinaemia#

IgA deficiencyMHC class II deficiency

B-cell deficiencyHyper-IgE syndrome

Secondary

Following chemotherapy#

Haematological malignancy#

Graft-versus -host disease

Interstitial lung disease# (traction bronchiectasis)

Autoimmune disease

Rheumatoid arthritis#

Ulcerative colitis


Sarcoidosis

Following surgeryInhaled foreign body

Chronic GORD

ABPA: allergic bronchopulmonary aspergillosis; Ig: immunoglobulin; MHC: major histocompatibility complex;

GORD: gastro-oesophageal reflux disease. #: more common conditions that should be considered whenmaking an initial diagnosis [2].

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However, these values are derived from a database of claims from 30 different healthcare insuranceplans made over a 2-year period. They are likely to underestimate the true prevalence as they exclude not only the uninsured population but also those who use alternative plans. It cannot,therefore, be claimed that they are truly representative of the real population prevalence. Theprevalence of non-CF bronchiectasis in Northern Ireland is estimated at around 5,000 in apopulation of approximately 2 million [13], leading to 300–400 admissions per annum for thetreatment of an infective exacerbation.

In children, bronchiectasis is less common. It can be extrapolated that the prevalence should befalling following the advent of improved antibiotic therapies and vaccination of children duringthe first year of life. Only two national studies have been reported with very different rates, 0.5 per100,000 population in Finland [14] and 3.7 per 100,000 population in New Zealand [15]. Incertain indigenous population groups, the prevalence is much higher, e.g. the New Zealand figuredoubles among the Maori and Pacific Islander populations [11, 15], Aboriginal rural communitieshave 14.7 per 1,000 population affected among those aged ,16 years [16] and 16 per 1,000population in Alaskan natives [17]. This is thought to occur due to an increased rate of severepulmonary infection in early childhood, due to a combination of socioeconomic factors rather

than solely a genetic predisposition.

Approach to diagnosis

The diagnostic approach to a patient with bronchiectasis should first establish that there is radio-logical evidence of airways dilatation and secondarily consider possible underlying conditions [1].

Table 2. Clinical findings in chronic obstructive pulmonary disease (COPD), asthma and bronchiectasis

COPD Bronchiectasis Asthma

Symptom

Cough + + +

Sputum production + ++ + /-Dyspnoea ++ + /- +

Wheeze + + /- ++

Haemoptysis - + -Fever + /- + -

Lethargy + /- + -

Recurrent infection + ++ +

Clinical signs

Finger clubbing No Extensive disease No

Breath sounds Q /wheeze Normal/ Q Normal/wheeze

Added sounds Wheeze Crackles WheezeLung function

Spirometry FEV 1Q, FVCQ FEV 1 /

FVCQFEV 1Q /normal FVCQ /normal

FEV 1 /FVCQ /normal

FEV 1Q /normal, FVC

normal FEV 1Q /normalReversibility 15% 40% Yes

Lung volumes Q / q Normal/ Q Normal

Transfer factor Normal Normal/ Q NormalHypoxia Yes Yes/no No

Radiology

Chest radiography Chronic inflammatory

changes, hyperinflation

Tramlines, ring shadows/normal Normal/

hyperinflationCT findings Hyperinflation, air-

trapping, bullae, may

have mildly dilated

airways or thickenedbronchial wall

Dilated bronchi, thickened

bronchial wall, lack of

tapering of bronchi,

bronchi visible in outer1–2 cm, air-trapping

Normal/air-trapping,

may have mildly dilated

airways or thickened

bronchial wall

CT: computed tomography; FEV 1: forced expiratory volume in 1 second; FVC: forced vital capacity;-: uncommon; + /-: occurs sometimes; +: common; ++: very common; Q: decrease; q: increase.

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People presenting with a chronic productive cough lasting for .4 weeks or recurrent episodes,with two or more episodes occurring over 8 weeks, should have the diagnosis of bronchiectasisconsidered [2]. In the scheme outlined in figure 1, all of the first-line investigations should beconsidered as routine in patients being investigated for bronchiectasis. Most people have already undergone some investigations prior to referral, such as a sputum culture, chest radiography orcomputed tomography (CT), which may guide further investigations.

Symptoms and physical findings

Cough productive of sputum is the most common symptom associated with bronchiectasis [1, 18–21].In some studies, 25% of patients do not report excessive daily sputum production, but describe amarked increase in volume during an exacerbation [1, 18]. Occasional haemoptysis is a frequentsymptom and is reported by half of all patients. This is often associated with a pulmonary exacerbation.Shortness of breath, fever and chest pain are also common complaints among non-CF bronchiectasispatients [18], although they are common symptoms in other chronic inflammatory lung disease thatmay coexist, e.g. COPD and asthma (table 2). Patients presenting with such symptoms who do notrespond as expected to usual therapy should raise the possibility of bronchiectasis and this should beinvestigated. Some symptoms point to specific diagnoses (table 3).

Physical examination

Physical findings are of modest help in the assessment of patients with bronchiectasis. The classicfindings of wet crackles and finger clubbing are now uncommon and should trigger investigationfor conditions associated with severe bronchiectasis, such as CF. Crackles with some associated

Diagnostic suspicion of bronchiectasis

Consider otherdiagnosis

Sweat [Cl-](CF)

Igs(CVID)

Nasal NO(PCD)

RF/autoantibodies(CTD)

Aspergillus IgE and IgG and

eosinophilia(ABPA)

Further studies in case of

diagnostic suspicion or doubt

EM studiesGenetics

Functional studies

GeneticsGenetics

Nasal PD

Vaccinationstudies: Pneumovax

and tetanus

First-line diagnosticinvestigations tobe considered in

all patients

Assessment offunctional status

and infection in allpatients

α1-AT levelsand phenotype

(α1-AT)

Negative

Positive

ChestHRCT scan

Sputum culture(including mycobacteria)

Spirometry Chestradiography

Figure 1. Diagnostic approach to bronchiectasis. HRCT: high-resolution computed tomography; [Cl -]: chloride

ion concentration; CF: cystic fibrosis; Ig: immunoglobulin; a1-AT: a1-antitrypsin; PCD: primary ciliary dyskinesia;

NO: nitric oxide; RF: rheumatoid factor; CTD: connective tissue disease; ABPA: allergic bronchopulmonaryaspergillosis; PD: potential difference; EM: electron microscopy; CVID: common variable immunodeficiency.

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wheeze are the most common findings, with finger clubbing now a rare feature, and usually associated with severe disease. Other aspects of examination should focus on clinical signs of associated diseases, such as CF, immune deficiency or a connective tissue disease.

Diagnostic tests

Blood tests

A complete blood count, although nonspecific, is important in monitoring the ongoing conditionof each individual patient. Haemoglobin level can be low secondary to anaemia of chronic disease,and, conversely, patients may be polycythaemic secondary to chronic hypoxia. An elevated whitecell count may indicate the presence of acute infection. The differential white cell count can reveallymphopenia, which may prompt further investigation for immunodeficiency syndromes oreosinophilia, which can occur in but is not diagnostic of allergic bronchopulmonary aspergillosis(ABPA).

C-reactive protein (CRP) is an acute-phase reactant commonly measured in respiratory patientswith acute exacerbations in order to assist in determining whether or not there is a systemicinflammatory response [1, 22, 23]. In bronchiectasis patients in a stable state, it has been shown

that CRP levels are elevated from baseline [22]. The CRP level also correlated with decline in lungfunction and severity of disease on high-resolution CT (HRCT) in the same series [22].

Radiology

Although suspected with a history of recurrent lower respiratory tract infection on a backgroundof chronic cough and sputum production, the diagnosis of bronchiectasis can only be confirmedradiologically [2]. The gold-standard investigation is HRCT. This was first described in 1982 [16],and permits a detailed examination of the lung architecture using a noninvasive technique.Historically, the diagnosis was based on bronchography, which involved instillation of a radio-

opaque dye into the airways and fluoroscopic screening. This technique has been superseded dueto the greater detail available in a safer more easily tolerated imaging method and is now obsolete.

Volumetric HRCT has some advantages over conventional HRCT as it provides more-detailedimages, but it is more prone to image degradation due to motion artefact and requires a higherradiation dose. Standard HRCT is appropriate for the majority of patients.

Findings on HRCT are bronchial wall thickening with dilatation of the bronchi to a diametergreater than that of the accompanying arteriole (the signet-ring sign); lack of normal tapering of bronchi/bronchioles on sequential slices; and visualisation of bronchi in the outer 1–2 cm ( fig. 2)[1, 23, 24]. The bronchiectatic changes in CF have been quantified using a number of scoring

systems, but the value of these in diagnosis or follow-up care has not been established.

The histopathological appearance of bronchiectasis has been further subcategorised as cylindrical,saccular and varicose, depending on the shape of the bronchi [25]. The true clinical significance of these subdivisions is unclear. However, cystic bronchiectasis has been associated with an increasedfrequency of exacerbation and more-clinically significant disease [24]. HRCT appearance can alsobe used to confirm any other parenchymal or bronchiolar pathology, such as interstitial lung

Table 3. Specific historical features suggestive of a particular diagnosis in adults

Primary ciliary dyskinesia Neonatal respiratory distress, middle ear disease, infertility

Cystic fibrosis Culture of Staphylococcus aureus, Pseudomonas aeruginosa or

Burkholderia cepacia complex, malabsorption symptoms,infertility, recurrent pancreatitis, nasal polyposis

Common variable immunodeficiency Recurrent respiratory, urinary, gastrointestinal and skin infections

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disease [25, 26]. The distribution of ectatic airways throughout the lung fields can be used to guideinvestigation of underlying causes, but most changes are nonspecific (table 4) [27, 28].

Although the diagnosis is confirmed radiologically using HRCT, a posteroanterior chestradiograph should be obtained as a baseline with which to compare future films in the event of acute exacerbation. Depending on the distribution of the bronchiectasis and the degree of damage,the chest radiograph may show minimal change from normal or be markedly abnormal.Traditionally, the radiographic changes associated with bronchiectasis are tramlines and ring

shadows [18]; these markings correspond to the thickened mucosa of the more-severely inflamedairways in transverse or cross-section.

a) b)

c)

Figure 2. High-resolution computed tomography

changes in bronchiectasis. a) Signet-ring sign, i.e.dilatation of the bronchi to a diameter greater than

that of the accompanying vessel. b) Visualisation of

the bronchi in the outer 1–2 cm. c) Thickenedbronchial walls. The circled areas indicate ring

shadows.

Table 4. High-resolution computed tomography features of bronchiectasis

General features

Bronchial dilatation (bronchus diameter greater than that of adjacent vessel)

Bronchial wall thickeningBronchial plugging

Areas of reduced attenuation (mosaic pattern)

Specific features ABPA: upper-zone central bronchiectasisCystic fibrosis: upper-zone bronchiectasis

NTM/MAC: Middle-lobe irregular branching and tree-in-bud appearance

ABPA: allergic bronchopulmonary aspergillosis; NTM: nontuberculous mycobacteria; MAC: Mycobacterium

avium-intracellulare complex.

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Once the diagnosis of bronchiectasis has been confirmed, a detailed clinical work-up should beundertaken in order to determine the extent of the impact on lung function, morbidity andprognosis, the underlying cause of the existing structural lung damage and the most prevalentinfecting organisms. The benefits of this are that not only can treatment be tailored to theindividual, but also a potentially treatable underlying condition may be uncovered [1, 24, 25].

A comprehensive clinical assessment, including a detailed history and physical examination, are

required to illicit any pointers towards a specific diagnosis. This should be followed up by extensiveinvestigation to allow determination of baseline functional status and lung function and to permitguidance of treatment. During the course of investigation, underlying conditions which are knownto have an association with bronchiectasis, albeit not a causative one, may be discovered.

Pulmonary function testing and other physiological factors

Forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) should be measuredat the time of the diagnostic evaluation and at least annually, more frequently in the setting of PCD, immunodeficiency or connective tissue disease [21, 24]. Spirometric results may be normalin some patients, although usually show a pattern of airflow limitation, with a decreased FEV1 anda reduced FEV1/FVC ratio. FVC may be normal or slightly reduced, although this finding alonemay be indicative of mucous impaction [2, 24]. Airway hyperresponsiveness has also beendemonstrated. In 40% of patients, an FEV1 reversibility of .15% following administration of b-agonist can be demonstrated [29]. In addition, 30–69% of patients who do not exhibit a reducedFEV1 at baseline, show a 20% decrease in FEV1 following histamine or methacholine challenge[30, 31], indicating clinically significant hyperresponsiveness. FEV1 has the strongest correlationwith severity of structural abnormality on HRCT [32, 33]; however, it correlates poorly withclinical fluctuations in disease course.

Full pulmonary function testing, including lung volumes and gas transfer coefficient, should be

carried out at the outset in adult presentations in order to give a picture of the overall functionalstatus of the lungs and also to assist in the diagnosis of underlying conditions [2]. Reduced lungvolumes and transfer factor should prompt consideration of underlying interstitial lung disease.Elevated lung volumes can be secondary to air-trapping or indicate mucous impaction of small-calibre airways.

Exercise testing, such as the incremental shuttle test and 6-minute walking test, are widely usedtools for the assessment of functional capacity in chronic pulmonary disease patients and can beapplied to bronchiectatic patients [34]. However, such tests have no value in diagnosis and thereare no data to support their use outside of clinical studies [35]. Limitation of exercise capacity has

not been shown to correlate with severity of airway damage on HRCT [36].Studies in post-resection patients have shown that exercise testing is more informative as anongoing assessment of lung function than static spirometry, particularly in patients whoseperformance or symptoms do not correlate with spirometric results [37].

Specific investigations

Cystic fibrosis

CF is the single most common cause of structural bronchiectasis in children and a reasonably common diagnosis in adults [2, 7, 24]. Increasingly, CF is diagnosed later in life, with many patientsnow being diagnosed in their third and fourth decades of life, and some even later [38–43]. Giventhis, all adults presenting with bronchiectasis and other features of CF should undergocomprehensive investigation in order to rule out CF. Pilocarpine iontophoresis for sweat chlorideion concentration ([Cl-]) measurement, should be carried out in all patients with bronchiectasis anda clinical suspicion of CF [2, 44]. The results should be interpreted as detailed in table 5. A sweat [Cl-]

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of ,30 mM effectively excludes CF as a diagnosis, although one CF-disease-causing mutation has beendescribed with normal sweat [Cl-] [44]. If the sweat [Cl-] is.60 mM, a diagnosis of CF is confirmed. If the sweat test result is 30–60 mM, the identification of one or more disease-causing mutationsdetermines which diagnostic category the patient falls into, CF or CF transmembrane conductanceregulator (CFTR)-related disorder (table 5) [44]. The diagnostic category of CFTR-related disorderhas recently emerged and describes single-organ disease, most frequently bronchiectasis, with anassociated sweat [Cl-] of 30–60 mM or one or two disease-causing mutations of the CFTR. In some

cases of diagnostic uncertainty, measurement of nasal potential difference may help to determineCFTR dysfunction. This may help to distinguish CF from a CFTR-related disorder [44].

Immunological investigations

A range of immunological abnormalities are associated with non-CF bronchiectasis [24]. Theprevalence of each in bronchiectasis varies from study to study. Humoral immunity can beaffected by low levels of any of the major immunoglobulin (Ig) classes, IgM, IgG and IgA [1, 24,45, 46]), and, in some cases, IgG subclasses, IgG1, IgG2, IgG3 and IgG4. The specific antibody response to polysaccharide and peptide vaccines provides additional information about the innate

immune response to antigenic stimulus [11].

Specific IgG subclass deficiency can be detected in serum or by checking the antibody response tovaccination with either pneumococcal or Haemophilus influenzae and tetanus toxoid vaccines.This is performed by measuring antibody levels prior to administration of a dose and again4 weeks later in order to investigate whether or not the individual has mounted an appropriateresponse [45]. Specific antibody response studies should be undertaken in consultation with animmunologist as interpretation of responses is complex, and a decision to treat patients withspecific deficiencies with Ig replacement requires a range of considerations and should undertakenby an immunologist with expertise in this area [2]. Replacing deficient IgG is usually effective in

reducing the frequency of infection and preventing further lung damage [45–47]. Neutrophil, T-cell, B-cell and complement disorders are a rare cause of bronchiectasis, and functional studiesshould be discussed with a specialist immunologist. All patients with an identified im-munodeficiency should be managed with a specialist immunologist [2].


PCD is an autosomal recessive disorder leading to immotile cilia, and occurs in 1 in 15,000 to 1 in40,000 of the population. It results in bronchiectasis and sinusitis and, in around half of cases,Kartagener’s syndrome (bronchiectasis, sinusitis and situs inversus) [10]. Diagnosis is based on exhaled

nasal nitric oxide levels and electron microscopy of nasal biopsy specimens [48]. Reduced nitric oxidelevel has a specificity of 98% and a positive predictive value of 92% for PCD [48], and may be used as ascreening tool to select those in whom nasal mucosal biopsy for electron microscopy is required. Thediagnostic gold standard is transmission electron microscopy of nasal biopsy specimens to view theultrastructural defects in the dynein arms within individual cilia [10]. Recent studies suggest that15% of patients with functional PCD show no ultrastructural defects and so there is a high false-negative diagnostic rate [10]. Genetic testing is now becoming more readily available and may gosome way towards overcoming limitations to ultrastructure as a diagnostic method [10].

Table 5. Sweat test diagnostic criteria for cystic fibrosis (CF)

Sweat [Cl-] mM Diagnostic conclusion

60 CF confirmed

30–60 Equivocal: further investigation required: CFTR DNA test 30 Not CF

[Cl-]: chloride ion concentration; CFTR: CF transmembrane conductance regulator.

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Allergic bronchopulmonary aspergillosis

IgE is a sensitive marker for ABPA if levels are .1,000 IU?L-1. Aspergillus precipitins or specificIgG directed against Aspergillus confirm the diagnosis. This condition responds well to acombination of high-dose oral corticosteroid and oral antifungal therapy [2, 49–51].

a1-Antitrypsin deficiency

In order to diagnose a1-AT deficiency, serum levels of a1-AT should be checked with thebiochemical phenotype requested in those patients with low levels, particularly if there is a family history of respiratory disease of young onset, or in family members who have never smoked orshow evidence of bullous disease on HRCT [9]. Genetic tests for the different genotypes (M, Z andS) are also now available.

Connective tissue disorders

Autoimmune disease covers a spectrum of conditions, which, although rare individually, can cause

bronchiectasis and, depending on the condition, may respond to directed treatment. These conditionscan be screened for by thorough history-taking and measurement of rheumatoid factor and otherspecific autoantibodies, such as antineutrophilic cytoplasmic antibody and cryoglobulin [2]. Morecommon autoimmune conditions with a strong association with bronchiectasis are rheumatoidarthritis and ulcerative colitis. It is recommended that patients attending specialist rheumatology orgastroenterology clinics for monitoring of these conditions who develop chronic cough or respiratory symptoms should undergo lung function testing and HRCT in order to rule out bronchiectasis.

Gastro-oesophageal reflux

Gastro-oesophageal reflux disease has been associated with bronchiectasis, although it is unclearwhether or not there is a direct causal relationship. If suspected, barium studies and fluoroscopy are indicated [2, 24].

Infection and sputum microbiology

Sputum microbiology is a key investigation in the diagnosis of patients with bronchiectasis [52].H. influenzae is the most-frequently isolated pathogen, being found in up to 35% of patients.Staphylococcus aureus, Streptococcus pneumoniae, Moraxella catarrhalis and Pseudomonas aeru-ginosa are also commonly identified organisms [53]. Aspergillus sp. may also be found, and may be

related to a diagnosis of ABPA. The presence of P. aeruginosa in sputum from people withbronchiectasis is associated with more-severe lung disease and may also have a negative impactupon prognosis [54, 55].

Monitoring disease activity

Monitoring disease activity in bronchiectasis can be difficult as there is little fluctuation in lungfunction as measured by spirometry [2]. The inflammatory response to infection in bronchiectasishas been shown to be compartmentalised, with higher concentrations of inflammatory mediatorsbeing found in the airways than in the systemic circulation [3, 56].

Patients’ symptoms are a very important guide to pulmonary exacerbations, with increased cough,sputum volume and purulence, and haemoptysis and reduced energy all being common symptoms.

Sputum analysis plays a pivotal role in the assessment of bronchiectasis, with antibiotic therapy being directed by the results of sputum culture and antibiotic sensitivity testing. Sputum cultureshould be performed at all outpatient reviews and when symptoms deteriorate.

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Although exacerbation rate does not clearly correlate with particular organisms, it has been shownto increase with increasing resistance of organisms to antibiotics [54]. Longitudinal studiesdemonstrate that subjects who carry the same organism after a 5-year period tend to carry increasingly resistant organisms, making exacerbations more difficult to treat successfully [54].Recent studies using molecular identification techniques in the sputum of CF patients haverevealed a wider spectrum of organisms in significant quantities than culture alone [57]. This hasled to the discovery that the CF microbiome is much more extensive and diverse than was

previously suspected. This is also likely to be the case in non-CF bronchiectasis. Moleculardiagnostic methods are considerably more expensive than culture-based methods and not freely available in most clinical microbiological laboratory settings.

Exacerbations are often associated with new isolates of bacteria and respond to antibiotictherapies. However, in many such episodes, no clinically significant organism can be identified asthe precipitating factor. Although it may be some time before molecular diagnostics enter clinicalpractice, it is worth bearing in mind, in the case of an infection not responding to standardantibiotic therapy, that there are other potentially pathogenic organisms present that may requirealternative treatment. As a rule of thumb, sputum culture is more likely to underestimate theprevalence of bacterial infection, and each positive culture should be treated with appropriateantibiotics.

A thorough structured approach to the investigation of patients with suspected bronchiectasis willenable further learning about the natural history of the condition and improve patient outcomesby appropriate direction of treatment.


None declared.

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5. Scala R, Aranne P, Palumbo V, et al. Prevalence, age distribution and aetiology of bronchiectasis; a retrospective

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9. Parr DG, Guest PG, Reynolds JH, et al. Prevalence and impact of bronchiectasis in a1-antitrypsin deficiency. Am J


10. Noone PG, Leigh MW, Sannuti A, et al. Primary ciliary dyskinesia: diagnostic and phenotypic features. Am J Respir

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11. Liote H. Etiological work-up for bronchectasis in adults. Rev Pneumol Clin 2004; 60: 255–264.

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13. Department of Health, Social Services and Public Safety. A Healthier Future. A Strategic Framework forRespiratory Conditions. Belfast, Department of Health, Social Services and Public Safety, 2006.

14. Sa yna jakangas O, Keistinen T, Tuuponen T, et al. Evaluation of the incidence and age distribution of

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15. Twiss J, Metcalfe R, Edwards E, et al. New Zealand national incidence of bronchiectasis is too high for a developed

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16. Chang AB, Grimwood K, Maguire G, et al. Management of bronchiectasis and chronic suppurative lung disease in

indigenous children and adults from rural and remote Australian communities. Med J Aust 2008; 189: 386–393.

17. Singleton R, Morris A, Redding G, et al. Bronchiectasis in Alaska native children: causes and clinical courses.

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18. Nicotra MB, Rivera M, Dale AM, et al. Clinical, pathophysiologic, and microbiologic characterization of

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19. Shields MD, Bush A, Everard ML, et al. BTS guidelines. Recommendations for the assessment and management of

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20. Patel IS, Viahos I, Wilkinson TM, et al. Bronchiectasis, exacerbation indices and inflammation in chronic


21. Ellis DA, Thornley PE, Wightman AJ, et al. Present outlook in bronchiectasis: clinical and social study and review

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22. Watt AP, Brown V, Courtney J, et al. Neutrophil apoptosis, proinflammatory mediators and cell counts in


23. Naidich DP, McCauley DI, Khouri NF, et al. Computed tomography of bronchiectasis. J Comput Assist Tomogr

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24. O’Donnell AE. Bronchiectasis. Chest 2008; 134: 815–823.

25. Hansell DM. Bronchiectasis. Radiol Clin North Am 1998; 36: 107–128.

26. Gudbjerg CE. Roentgenologic diagnosis of bronchiectasis: an analysis of 112 cases. Acta Radiol 1955; 43:

209–225.

27. Remy Jardin M, Amara A, Campistron P, et al. Diagnosis of bronchiectasis with multislice spiral CT: accuracy of

3-mm-thick structured sections. Eur Radiol 2003; 13: 1165–1171.

28. Reiff DB, Wells AU, Carr DH, et al. CT findings in bronchiectasis: limited value in distinguishing between

idiopathic and specific types. AJR Am J Roentgenol 1995; 165: 261–267.

29. Murphy MB, Reen DJ, Fitzgerald MX. Atopy, immunological changes, and respiratory function in bronchiectasis.

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30. Swaminathan S, Kuppurao KV, Somu N, et al. Reduced exercise capacity in non-cystic fibrosis bronchiectasis.

Indian J Pediatr 2003; 70: 553–556.

31. Pang J, Chan HS, Sung JY. Prevalence of asthma, atopy, and bronchial hyperreactivity in bronchiectasis:

a controlled study. Thorax 1989; 44: 948–951.

32. Sheehan RE, Wells AU, Copley SJ. A comparison of serial computed tomography and functional change in

bronchiectasis. Eur Respir J 2002; 20: 581–587.

33. Roberts HR, Wells AU, Milne DG. Airflow obstruction in bronchiectasis: correlation between computed

tomography features and pulmonary function tests. Thorax 2000; 55: 198–204.34. Lee AL, Button BM, Ellis S, et al. Clinical determinants of the 6-minute walk test in bronchiectasis. Respir Med

2009; 103: 780–785.

35. Newall C, Stockley RA, Hill SL. Exercise training and inspiratory muscle training in patients with bronchiectasis.

Thorax 2005; 60: 943–948.

36. Edwards EA, Narang I, Li A, et al. HRCT lung abnormalities are not a surrogate for exercise limitation in


37. Tsubota N, Yanagawa M, Yoshimura M, et al. The superiority of exercise testing over spirometry in the evaluation

of postoperative lung function for patients with pulmonary disease. Surg Today 1994; 24: 103–105.

38. McCloskey M, Redmond AOB, Hill B, et al. Clinical features associated with a delayed diagnosis in CF. Ir J Med Sci

2000; 67: 402–407.

39. King PT, Freezer NJ, Holmes PW, et al. Role of CFTR mutations in adult bronchiectasis. Thorax 2004; 59:

357–358.40. Hubert D, Fajac I, Bienvenu T, et al. Diagnosis of cystic fibrosis in adults with diffuse bronchiectasis. J Cyst Fibros

2004; 3: 15–22.

41. Gilljam M, Ellis L, Corey M, et al. Clinical manifestations of cystic fibrosis among patients with diagnosis in

adulthood. Chest 2004; 126: 1215–1224.

42. Paranjape SM, Zeitlin PL. Atypical cystic fibrosis and CFTR-related disease. Clin Rev Allergy Immunol 2008; 35:

116–123.

43. Knowles MR, Durac PR. What is cystic fibrosis. N Engl J Med 2002; 347: 439–442.

44. DeBoeck K, Wilschanski M, Castellani C, et al. Cystic fibrosis: terminology and diagnostic algorithms. Thorax

2006; 61: 627–635.

45. Stead A, Douglas JG, Broadfoot CJ, et al. Humoral immunity and bronchiectasis. Clin Exp Immunol 2002; 130:

325–330.

46. Bernatowska E, Madalinski K, Janowicz W, et al. Results of a prospective controlled two-dose crossover study withintravenous immunoglobulin and comparison (retrospective) with plasma treatment. Clin Immunol

Immunopathol 1987; 43: 153–162.

47. Eijkhout HW, van Der Meer JW, Kallenberg CG, et al. The effect of two different dosages of intravenous

immunoglobulin on the incidence of recurrent infections in patients with primary hypogammaglobulinemia:

a randomized, double-blind, multicenter crossover trial. Ann Intern Med 2001; 135: 165–174.

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48. Horvath I, Loukides S, Wodehouse T, et al. Comparison of exhaled and nasal nitric oxide and exhaled carbon

monoxide levels in bronchiectatic patients with and without primary ciliary dyskinesia. Thorax 2003; 58: 68–72.

49. Greenberger PA, Miller TP, Roberts M, et al. Allergic bronchopulmonary aspergillosis in patients with and without

evidence of bronchiectasis. Ann Allergy 1993; 70: 333–338.

50. Bahous J, Malo JL, Paquin R, et al. Allergic bronchopulmonary aspergillosis and sensitization to Aspergillus

fumigatus in chronic bronchiectasis in adults. Clin Allergy 1985; 15: 571–579.

51. Wang JL, Patterson R, Rosenberg M, et al. Serum IgE and IgG antibody activity against Aspergillus fumigatus as a

diagnostic aid in allergic bronchopulmonary aspergillosis. Am Rev Respir Dis 1978; 177: 917–927.

52. Angrill J, Agusti C, de Celis R, et al. Bacterial colonisation in patients with bronchiectasis: microbiological pattern

and risk factors. Thorax 2002; 57: 15–19.

53. Kelly MG, Murphy S, Elborn JS. Bronchiectasis in secondary care: a comprehensive profile of a neglected disease.

Eur J Intern Med 2003; 14: 488–492.

54. Wilson CB, Jones PW, O’Leary CJ, et al. Effect of sputum bacteriology on the quality of life of patients with


55. King PT, Holdsworth SR, Freezer NJ, et al. Microbiologic follow-up study in adult bronchiectasis. Respir Med

2007; 101: 1633–1638.

56. Hill SL, Morrison HM, Burnett D, et al. Short term response of patients with bronchiectasis to treatment with

amoxycillin given in standard or high doses orally or by inhalation. Thorax 1986; 41: 559–565.

57. Tunney MM, Field TR, Moriarty TF, et al. Detection of anaerobic bacteria in high numbers in sputum from


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Chapter 5

Radiological features

of bronchiectasisP.L. Perera* and N.J. Screaton #

Summary

Imaging plays a crucial role in the diagnosis and monitoring of

bronchiectasis and the management of complications. Chestradiography is useful as an initial screening tool and during acute exacerbations, but has limited sensitivity and specificity.High-resolution computed tomography (HRCT) is the refer-ence standard for diagnosis and quantification of bronchiecta-sis, providing detailed morphological information. Computedtomography (CT) is also valuable in diagnosing and managing complications. Routine surveillance using HRCT has beenmooted, particularly in cystic fibrosis (CF), where advances in

treatment have increased life expectancy considerably, butcumulative radiation dose remains a concern.

Pulmonary magnetic resonance imaging is an evolving technique that provides both structural and functional infor-mation. Its advantage is the lack of ionising radiation. Limita-tions include cost, availability and its inferior spatial resolutioncompared to CT. The technique requires further evaluation, buthas potential benefits where serial follow-up imaging is being considered, such as in CF. Evaluation of mucociliary clearanceusing radionuclide scintigraphy may be of value, particularly indrug development.

Keywords: Bronchiectasis, cystic fibrosis, diagnostic imaging,magnetic resonance imaging, mucociliary clearance, spiralcomputed tomography

*Dept of Radiology, Norfolk andNorwich University Hospital,

Norwich, and#Diagnostic Imaging Dept, PapworthHospital, Papworth Everard, UK.

Correspondence: N.J. Screaton,Diagnostic Imaging Dept, PapworthHospital, Papworth Everard, CB233RE, UK, [email protected]


B ronchiectasis is characterised by irreversible dilation of bronchi, which may be focal or diffuse,and usually occurs with associated inflammation. Its pathogenesis is complex and often

multifactorial, with bronchial wall inflammation, bronchial wall weakness and infection oftenoccurring in parallel and with numerous aetiological factors. Since it was first described by LAENNEC [1] in 1819, there have been considerable advances in the understanding, diagnosis andtreatment of bronchiectasis. Imaging now forms the cornerstone of diagnosis of bronchiectasis andits complications and plays an increasing role in disease monitoring and therapeutic planning. Thepresent review focuses on imaging features in bronchiectasis and their role in diagnosis andmonitoring of disease. Several imaging modalities are available, with varying strengths and

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limitations, which are outlined below. The choice of diagnostic/monitoring strategy shows somevariation depending on access to each modality and interpretive expertise. Image-guidedintervention, such as percutaneous pleural aspiration/drainage and angiography with embolisationplay important roles in treating complications, but are beyond the scope of the present review.

Chest radiography

Chest radiography (CXR) is usually the initial study performed in both suspected bronchiectasisand the evaluation of nonspecific respiratory symptoms, such as dyspnoea and haemoptysis, whenbronchiectasis may be identified incidentally. Signs on CXR include the identification of parallellinear densities, tram-track opacities, or ring shadows reflecting thickened and abnormally dilatedbronchial walls. These bronchial abnormalities form a spectrum from subtle or barely perceptible5-mm ring shadows to obvious cysts. Tubular branching opacities conforming to the expectedbronchial branching pattern may result from fluid or mucous filling of bronchi. Peribronchialfibrosis results in a loss of definition of vessel walls ( fig. 1) [2–5].

Signs of complications/exacerbations, such as patchy densities due to mucoid impaction and

consolidation, volume loss secondary to bronchial mucoid obstruction or chronic cicatrisation,are also seen. In the more diffuse forms of bronchiectasis, such as cystic fibrosis (CF), generalisedhyperinflation and oligaemia are often present, consistent with severe small airways obstruction.

The radiograph may raise the initial suspicion of bronchiectasis, triggering more definitive imaging.However, its projectional nature and limited contrast resolution lead to limited sensitivity andspecificity, particularly in mild disease. CXR also plays a role in the follow-up of bronchiectasis andmanagement of exacerbations, although, again, the relative insensitivity to change is highlighted by proponents of computed tomography (CT) and magnetic resonance (MR) imaging (MRI) [2–5].

The reported accuracy of CXR has changed over the years as the management emphasis has shifted

from being reactive to complications to one of early detection and proactive management, and as thediagnostic reference standard has shifted from bronchography to CT. In 1955, GUDJBERG [6]reported only 7.1% of 114 bronchiectatic patients having a normal CXR, perhaps reflecting the moreflorid nature of the condition during this period. In 1987, CURRIE et al. [7] reported an overallsensitivity of 47%, and only 13% on a lobar basis, in 19 patients with bronchographically provenbronchiectasis. The same study confirmed significant interobserver variation in CXR interpretation,with two experienced readers disagreeing on the diagnosis of bronchiectasis in 22% of cases [7].

In comparison to CXR, CT is both more sensitive and provides more specific information. BHALLA

et al. [8] showed that, out of a total of 162 bronchopulmonary segments reviewed, bronchiectasiswas detected in 124 on high-resolution CT (HRCT) and only 71 on CXR.

Radiographic scoring systems, such as those of CHRISPIN and NORMAN [9] and BRASFIELD et al. [10],have been developed and subsequently modified for patients with CF. These can be useful clinically,but are more commonly used for comparison in research. CLEVELAND et al. [11] showed that a scorebased on the scoring system of BRASFIELD et al. [10] could be used to assess the longitudinalprogression of lung disease in CF, and was at least as effective as spirometry in this regard.

Although CXR has limitations in specificity in diagnosing bronchiectasis and in detecting early orsubtle changes, it is useful for assessing more florid cases of bronchiectasis, in CF and in follow-upof bronchiectatic patients.

Computed tomography

The CT signs of bronchiectasis were first described by NAIDICH et al. [12] in 1982. Although initialstudies using 8–10-mm slice thickness showed low sensitivity [13–15], the advent of HRCT led tomarkedly improved sensitivity, resulting in HRCT replacing bronchography as the diagnosticreference standard. GRENIER et al. [16] showed that HRCT with 1.5-mm collimation at 10-mm

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intervals was accurate in the recogni-tion of bronchiectasis using broncho-graphy as the gold standard in 36patients.

Multidetector CT (MDCT) with vol-umetric acquisition further increases

the sensitivity in detection of subtlenontapering airways. DODD et al. [17]compared contiguous 1-mm MDCTwith 1-mm incremental HRCT with10-mm interspaces in 61 bronchiec-tatic patients and 19 normal controls.Using MDCT as the gold standard,the sensitivity, specificity and positiveand negative predictive values of in-cremental HRCT in detecting bron-chiectasis were 71, 93, 88 and 81%,respectively. Interobserver agreementfor the presence, extent and severity of bronchiectasis was also better forMDCT (kappa 0.64, 0.5 and 0.48,respectively) than for incrementalHRCT (kappa 0.65, 046 and 0.25,respectively).

Optimal HRCT technique is impor-tant for maximising diagnostic accu-

racy. Importantly, thin slices of 1–2 mm and a high-resolution lungreconstruction algorithm are usedto optimise spatial resolution. Incre-mental imaging with 10-mm sliceinterspace reduces radiation dose,but helical MDCT permits volu-metric acquisition in a single breath-hold, which is often the preferredtechnique. Electronic images should

be viewed in stack/cine mode us-ing the appropriate window set-tings (centred -400– -950 HU; width1,000–1,600 HU). Difficulties in diag-nosing bronchiectasis can arise fromcardiorespiratory motion artefact, useof inappropriate window widths andlevels, and the relatively thick-walledappearance of bronchial walls on

expiratory scans. Tractional airway dilation associated with pulmonary fibrosis has a characteristic

corkscrew appearance and should be differentiated from pathological bronchiectasis.

CT signs of bronchiectasis

Bronchial dilation, the cardinal sign of bronchiectasis, is characterised on HRCT by abronchoarterial ratio (BAR) of .1, lack of bronchial tapering, and visibility of airways within1 cm of the pleural surface or abutting the mediastinal pleural surface [2, 12, 16, 18, 19].

a)

b)

Figure 1. Chest radiography showing a) cystic bronchiectasis with

multiple cystic airspaces and b) cylindrical bronchiectasis and tram-track opacities in a cystic fibrosis patient.

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The different morphological types of bronchiectasiscorresponding to the bronchographic classification of R EID [20] show differing radiological features [16, 21],but this is of little relevance in terms of aetiology andrather reflects varying severity of the disease. Although,in cylindrical bronchiectasis, there is uniform dilationof airways with nontapering walls, in varicose bronch-

iectasis, dilated bronchi have a beaded appearance and,in cystic bronchiectasis, grosser bronchial dilation givesthe appearance of cysts (fig. 2).

The BAR refers to the ratio of the internal bronchialdiameter to the diameter of the accompanying pul-monary artery at an equivalent branching level. A BAR of .1 is considered abnormal [14, 15, 19] and is other-wise known as the signet-ring sign (fig. 3).

The accuracy of the BAR can be limited by a number of factors, including physiological

variation and orientation of the bronchovascular bundle with respect to the imaging plane[16, 22, 23]. Comparison is best performed on perpendicularly orientated airways. Whenoblique to the acquisition plane, airways and vessels appear ovoid and their short axis shouldbe compared.

Physiological influence on BAR was highlighted by LYNCH et al. [23], who showed that 59% of 27normal volunteers living in Colorado, USA (1,600 m above sea level) had at least one bronchusthat had an internal diameter larger than its accompanying artery. KIM et al. [18] confirmed thisenvironmental influence on BAR by demonstrating that residents living at 1,600 m exhibitedsignificantly higher BARs than those living at sea level (0.76 and 0.62, respectively; p,0.001).

Physiological variation can also occur due to regional hypoxia, and so secondary vasoconstrictioncausing apparent bronchial dilation must be recognised in order to prevent a spurious diagnosisof bronchiectasis. Conversely, if there is arterial dilation (e.g. due to pulmonary arterialhypertension), bronchiectasis could be missed. A practical problem in assessing BAR is the need toidentify the accompanying artery, which may be difficult in the presence of other lung pathology,such as consolidation. In the setting of consolidation, the presence of bronchial dilation may be areversible phenomenon and so caution should be observed when interpreting CT data during anacute illness.

Although objective measurement may be performed, visual inspection is the usual method of assessingbronchial dilation. DIEDERICH et al. [24] showed this to

have good interobserver agreement for detection (kappa0.78) and severity assessment (kappa 0.68).

Lack of bronchial tapering or tram-track appearance of the parallel bronchial walls is a sensitive feature of bronchiectasis often identified in more horizontally orientated airways in the mid-zones. KANG et al. [25]showed that lack of tapering on HRCT was moresensitive than bronchial dilation in bronchiectasis (79and 60%, respectively) using pathology as the reference

standard. However, the sign can be difficult tointerpret in nonvolumetric CT studies. KIM et al. [18]demonstrated lack of tapering on HRCT in 95% of patients with bronchiectasis, but also in 10% of normalsubjects. It has been suggested that bronchial diametershould remain unchanged for at least 2 cm distal to abranching point for this sign to be robust (fig. 4) [26].

Figure 2. High-resolution computed tomo-

graphy image showing cystic bronchiectasis

(same patient as in fig. 1a).


graphy image demonstrating signs of

bronchiectasis, the signet-ring sign (shortarrow) and peripheral airway visible within

1 cm of the pleural surface (long arrow).

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Visibility of peripheral airways is another importantdirect sign of bronchiectasis [17]. Current HRCTtechniques permit visualisation of airways of up to2 mm in diameter and walls of around 0.2 mm inthickness. KIM et al. [18] showed that normal bronchi arenot visualised within 1 cm of the costal pleura, but may be seen within 1 cm of the mediastinal pleura. Visible

bronchi within 1 cm of the costal pleura or abutting themediastinal surface were seen in 81 and 53% of HRCTimages of known bronchiectatic patients (fig. 4).

Ancillary signs commonly identified in bronchiectaticpatients include bronchial wall thickening, mucoidimpaction and air-trapping. Minor volume loss can beseen in the early stages of bronchiectasis. Larger areas of

collapse secondary to mucous plugging may be seen in more advanced disease. Patchy consolidation is sometimes seen reflecting superimposed infection.

Bronchial wall thickening is often seen in the presence of bronchiectasis [25], but is a variablenondiagnostic feature. It may result from reversible airway wall inflammation [27] or smoothmuscle hypertrophy and fibroblastic proliferation. Minor bronchial wall thickening has, however,also been described in normal individuals, asthmatics, asymptomatic smokers and during lowerrespiratory tract infections [23, 28].

Identification of bronchial wall thickening on HRCT is often made subjectively and is associatedwith significant interobserver variation, with no universally agreed definition. R EMY-JARDIN andR EMY [28] defined a thickened bronchus as being twice as thick as a normal bronchus; however,this definition is difficult in diffuse disease DIEDERICH et al . [24] defined a thick-walled bronchus

by an internal diameter of ,

80% of its external diameter and showed good interobserveragreement (kappa 0.66). However, this can lead to overdiagnosis of thickening in the presence of bronchoconstriction and underestimation with marked bronchodilation. An alternative approach,used by BHALLA et al. [8] in CF and subsequently modified by R EIFF et al. [29], is to comparebronchial wall thickness to the diameter of the adjacent artery. As with assessment of BAR,peribronchial fibrosis and consolidation pose practical difficulties in identifying accompanyingvessels (fig. 5).

Mucous plugging of dilated bronchi is readily identified, causing either complete or partialluminal filling (fig. 5). Plugging of the smaller peripheral airways and peribronchiolar in-flammation are characterised by a tree-in-bud appearance, with V- and Y-shaped branching

nodular opacities [30]. Mucous plugging was scored interms of number and generation of involved bronch-opulonary segments using the scoring system of BHALLA

et al. [8], and may be reversible.

Air-trapping results either from mucous plugging andabnormal bronchial compliance [31] or inflammation/fibrosis of the small airways [2]. On HRCT, air-trapping is characterised by patchy lobular areas of low attenuation with regional vasoconstriction, which

causes a mosaic attenuation pattern, accentuated onexpiratory images, although inspiratory images areusually characteristic (fig. 6). Air-trapping and bron-chiectasis coexist in the same lobe in approximately half of cases [25]. Whether it is the bronchiectasis andrecurrent infections driving obliterative bronchiolitis(OB) or primary small airways disease that precedes the

Figure 4. High-resolution computedtomography image showing nontapering

bronchi, in keeping with bronchiectasis.

*


graphy image demonstrating bronchiectasis

with bronchial wall thickening (asterisk) andmucous plugging (arrow) in the right lower

lobe.

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onset of bronchiectasis is debated, and may vary [31].The latter is supported both by the observation that, inpatients with CT-proven bronchiectasis, expiratory HRCT identifies air-trapping in 17% of lobes with nobronchiectatic features and that, in patients withrheumatoid arthritis (RA)-associated OB, the onset of symptoms and obstructive function may predate the

onset of bronchiectasis by several years [32].

Imaging and aetiology of bronchiectasis

There are many aetiologies associated with bronch-iectasis, but a specific underlying cause is found in,40% of patients [33]. In some cases, the distributionand pattern of bronchiectasis on HRCT may suggestthe aetiology. Allergic bronchopulmonary aspergillosis(ABPA) typically demonstrates an upper zone and central predominance [34–37], hypogamma-

globulinaemia may be associated with bronchiectasis with disproportionate bronchial wallthickening, middle lobe predominance is common in immotile cilia syndrome [38] and idiopathicbronchiectasis often has a lower lobe distribution [39].

However, in a large study comparing HRCT features in bronchiectasis of defined aetiology withidiopathic bronchiectasis, R EIFF et al. [29] concluded that, although some HRCT features weremore common in some aetiological groups, the differences were not sufficient to be diagnostic. L EE

et al. [40] reinforced this observation in a study of 108 bronchiectatic patients in whom the correctcause was identified on CT in only 45% of cases. A confident diagnosis was asserted in a minority (9%) and was correct in only 35%. Interobserver agreement in likely aetiology was also poor(kappa 0.2) [40]. However, more recently, CARTIER et al. [41] obtained accurate diagnoses on the

basis of HRCT in 61% of 82 patients with bronchiectasis of known cause, with moderately goodagreement (kappa 0.53). Confident and accurate diagnosis was made in 44% of patients (kappa0.53). Accuracy was highest in CF (68%), previous tuberculosis (67%) and ABPA (56%). Part of the reason for the higher number of accurate diagnoses was attributed to the exclusion of patientsin whom the aetiology of bronchiectasis was not known. They concluded that the combination of radiological pattern and clinical scenario would have improved the accuracy of the evaluation.

HRCT is important in the assessment of mycobacterial infection. This is particularly true of nontuberculous mycobacteria (NTM), where the diagnosis is often first suggested on HRCT. CTsigns of NTM include bronchiectasis, nodules, tree-in-bud opacity, patchy consolidation and

cavities, often affecting the upper lobes and superior segments of lower lobes in the classic subtypeand middle lobe/lingula in the nonclassic subtype [42]. The presence of this combination of features with a middle lobe and lingual predominance, especially in the setting of elderly femaleswith no underlying malignancy or immunocompromise, is particularly suggestive of nonclassicNTM [43, 44]. Bronchiectasis is more common in NTM infection, being seen in up to 94% of patients with Mycobacterium avium complex and 27% of patients with M. tuberculosis [45].

Bronchiectasis in CF usually has a bilateral, proximal, parahilar and upper lobe predominance.Other findings include bronchial wall thickening, peribronchial interstitial thickening, mucousplugging, tree-in-bud opacification, superadded consolidation and mosaic attenuation. SHAH et al.[27] assessed the CT changes in 19 symptomatic adult CF patients before and after 2 weeks of

therapy and identified air–fluid levels in bronchiectatic airways, mucous plugging, centrilobularnodules and peribronchial thickening as potentially reversible signs.

Bronchiectasis with a central or proximal predominance is the characteristic finding in ABPA(fig. 7a). R EIFF et al. [29] showed that the prevalence of central bronchiectasis was higher in ABPA(11 out of 30) than in idiopathic bronchiectasis (26 out of 179) (p,0.005). However, the sensi-tivity of the observation of central bronchiectasis in diagnosing ABPA was only 37%. PANCHAL et al. [46]

Figure 6. Inspiratory high-resolution com-

puted tomography image showing bronch-

iectasis and w idespread areas of lowattenuation, representing air-trapping.

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demonstrated central bronchiectasis in 85% of lobesand 52% of lung segments in a series of 23 patientswith ABPA. Other common findings in ABPA includemucous plugging, high-attenuation mucus, tree-in-bud opacities, atelectasis, peripheral consolidation orground-glass opacification, mosaic perfusion and air-trapping. The bronchiectasis is often cystic or varicose.

WARD et al. [47] assessed CT images from 44asthmatic patients with ABPA and 38 without andfound much higher levels of bronchiectasis, centri-lobular nodules and mucous impaction in ABPA.They concluded that randomly distributed predomi-nantly central moderate-to-severe bronchiectasisaffecting three or more lobes, bronchial wall thicken-ing and centrilobular nodules in asthmatics is highly suggestive of ABPA (fig. 7b).

High-attenuation mucous plugs are reported to occurin 18–28% of patients with ABPA, and, if observed, arethought to be characteristic [48–50]. In a study of 155patients with ABPA, AGARWAL et al. [48] found thissign in 29 patients, and that it correlated with greaterseverity and greater likelihood of relapse.

In summary, there are some recognised clinicalconditions in which assessment of bronchiectasis formsan important part of management. CT images inbronchiectatic patients should be examined for features

suggesting ABPA, CF, immotile cilia, opportunistmycobacteria and tracheobronchomegaly, but these observation need to be correlated withclinical and laboratory findings.

CT scoring of bronchiectasis

Although the extent, severity and distribution of bronchiectasis may be evaluated subjectively,more-robust objective scoring systems have been developed particularly for use in the researcharena. With the development of novel software tools, it is now possible to objectively quantify parameters, such as airway wall area and volume, in a semi-automatic manner. Both subjective

and objective quantification permit correlations between structure and function to be evaluated.

CT scoring systems are based on collective scores for the extent and distribution of a rangeof morphological abnormalities, including bronchial dilation, bronchial thickening, abscesses,mucous plugging, emphysema, collapse and consolidation.

The HRCT score of BHALLA et al. [8] was devised to evaluate the severity of CF in an objectivemanner. Severity of bronchial dilation and thickening were defined relative to the adjacentpulmonary artery, and other parameters were scored according to the number of bronchopul-monary segments involved, as shown in table 1.

This scoring system has been modified many times, and has also been adapted for use in MRIassessment of CF. Modifications have included incorporation of additional findings, such as air-trapping/mosaic attenuation, ground-glass opacification, acinar nodules and septal thickening,with some scores being per segment and others based on lobar scoring. Each scoring systemattempts to produce both a total score, by combining features, and specific morphological scores.These have been demonstrated to be more sensitive to disease and show better correlation withboth clinical features and lung function than the CXR-based scoring systems. OIKONOMOU et al. [51]

a)

b)

Figure 7. High-resolution computed tomo-graphy showing a) proximal bronchiectasis

affecting segmental airways and b) high-

attenuation mucous plugs in patients withallergic bronchopulmonary aspergillosis. No

intravenous contrast medium was used in (b).

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suggested a simplified scoring system evaluating severity of bronchiectasis, bronchial wall thickeningand atelectasis consolidation. They found strong correlation between the simplified scores and thecomplete scores.

SHAH et al. [27] used a modified Bhalla score in bronchiectatic patients undergoing HRCT atbaseline and 2 weeks after exacerbation in order to identify reversible findings, and showed thatair–fluid levels, centrilobular nodules, mucous plugging and peribronchial thickening improvedfollowing treatment in 100, 36, 33 and 11% of cases, respectively.

DE JONG et al. [52] compared the original scoring system of BHALLA et al. [8] and four modifiedBhalla systems [53–56]. Three observers reviewed thin-slice CT images of 25 children with CFusing the various scoring systems. Interobserver variability was analysed using kappa coefficientsand found to be generally good (kappa .0.76; p,0.05). However, inter- and intra-observeragreement was less for mild disease, as well as for parameters such as mosaic perfusion, acinarnodules and airspace disease. All five scoring systems correlated strongly with forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), forced expiratory flow between 25 and75% of vital capacity (FEF25–75), FEV1/FVC ratio and each other.

Quantitative computerised evaluation of the airways presents a number of challenges, includingobtaining a plane perpendicular to the airway, exclusion of the adjacent artery, determining the

borders of the bronchus, artefacts and partial volume averaging. Three different methods havebeen used to obtain airway measurements, full width at half maximum, model fitting approachesand boundary fitting approaches [19]. A detailed description of these techniques is beyond thescope of the present chapter.

GORIS et al. [57] looked at automated evaluation of the extent of air-trapping in 25 patients withmild CF compared to 10 controls; six anatomically matched CT slices were obtained during

Table 1. Summary of computed tomography scoring system

Category Score

0 1 2 3

Severity of bronchiectasis Absent Mild (luminal

diameter slightly

greater than that

of adjacentblood vessel)

Moderate (luminal

diameter 2–3 times

that of adjacent

blood vessel)

Severe (luminal

diameter .3 times

that of adjacent

blood vessel)

Peribronchial thickening Absent Mild (wallthickness equal

to diameter of

adjacent vessel)

Moderate (wallthickness greater

than and up to

twice the diameter

of adjacent vessel)

Severe (wallthickness .2 times

the diameter of

adjacent vessel)

Extent of bronchiectasis Absent Present Present Present

BP segments n 1–5 6–9 .9Extent of mucous plugging Absent Present Present Present

BP segments n 1–5 6–9 .9

Sacculations or abscesses Absent Present Present Present

BP segments n 1–5 6–9 .9Bronchial divisions

involved (bronchiectasis/

plugging) generations

Absent Up to 4th Up to 5th Up to 6th and distal

Bullae Absent Unilateral Bilateral Present

Bullae n not .4 not .4 .4

Emphysema Absent Present Present

BP segments n 1–5 .5Collapse/consolidation Absent Subsegmental Segmental/lobar

BP: bronchopulmonary. Reproduced from [8] with permission from the publisher.

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inspiration and expiration. Computerised lung segmentation was performed and automatedsoftware used to quantify air-trapping, using analysis of a histogram of the distribution of densitiesin the lung, and assessing contiguous low-attenuation voxel regions. In mild CF, air-trapping didnot correlate with global pulmonary function test (PFT) results, except for the ratio of residualvolume (RV) to total lung capacity (TLC); however, the size of the air-trapping defects was thebest discriminator between patients and control subjects (p,0.005).

KIRALY et al. [58] looked at fully automated methods of obtaining three-dimensional (3D) imagesand quantification of airway abnormalities. Working from thin-slice image acquisition and usingcomputerised segmentation techniques, they obtained 3D images of the airways with colour-codedmaps showing BAR, wall thickness and mucous plugging. These have, however, not been fully clinically validated.

Although these objective tools are interesting, further studies are required to evaluate thevarious computerised imaging parameters and their relation to functional and clinical findingsin bronchiectasis. A note of caution was raised by MATSUOKA et al. [59], who used semi-automatic image processing to assess the airways of 52 asymptomatic patients with nocardiopulmonary disease. They found that luminal area and wall area increased in 10 and 29%

of subjects, respectively, suggesting caution in over-reliance on changes in airway calibre indisease monitoring.

Structure–function relationships

Relationships between HRCT data and functional and clinical characteristics have been widely explored. WONG-YOU-CHEONG et al. [60] showed a clear negative correlation between FEV1 andextent of bronchiectasis on HRCT (p,0.002; r5 -0.43). SMITH et al. [61] showed correlationbetween extent of bronchiectasis on HRCT and both dyspnoea (p,0.01; r50.38) and FEV1

(p,0.01; r5 -0.43). More recently, DE JONG et al. [52] showed strong correlations between five

scoring systems [8, 53–56] and FEV1 (r5 -0.69– -0.73), FEF25–75 (r5 -0.76– -0.82) and FEV1/FVC ratio (r5-0.72– -0.78). Correlation with FVC was moderate (r5 -0.54– -0.58).

Authors have investigated which morphological abnormalities are most strongly associated with afunctional deficit. LYNCH et al. [62], in a study of 261 bronchiectatic patients, found significantcorrelation between severity of bronchiectasis, FEV1 (r5 -0.362) and FVC (r5 -0.362), andbetween bronchial wall thickening and FEV1 (r5 -0.367) and FVC (r5 -0.239). Cystic bron-chiectasis was found to show worse PFT results than cylindrical or varicose disease.

In a study of 100 patients with bronchiectasis, R OBERTS et al. [63] found good correlation betweenFEV1 and bronchial wall thickening (r5 -0.51; p50.00005) and extent of decreased attenuation on

expiratory HRCT (r5 -0.55, p50.00005) on univariate analysis. These were the only factors thatindependently correlated with degree of airflow limitation on multivariate analysis. In this study,obstructive lung function was not strongly associated with severity of bronchiectasis,bronchodilation, or retained sections in bronchiectasis (r5 -0.42, -0.35 and -0.19, respectively,on univariate analysis). Bronchial dilation as an independent factor was positively associated withairflow obstruction on regression analysis (r250.42). The authors concluded that airflow limitation in bronchiectasis occurred mainly due to inflammatory or obstructive/constrictivebronchiolitis. They also suggested that areas of low attenuation attributed to emphysema inbronchiectatic patients in previous studies (e.g. [64]) should be interpreted with caution,suggesting that the emphysema demonstrated was often due to air-trapping related to intrinsic

small airways disease rather than emphysema, as evidenced by preserved gas transfer in the both of these studies.

HRCT scoring can also be correlated with clinical parameters. In a study of 61 CF children,baseline and follow-up PFT and HRCT scores were compared to the number of respiratory exacerbations over 2 years. Only the HRCT score (r50.91; p50.001) and bronchiectatic score(r50.083; p50.01) correlated significantly with exacerbation frequency. All HRCT parameters

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progressed over this time period except for bronchial wall thickening and mucous plugging,suggesting that these are reversible features [65]. OOI et al. [66] studied 60 patients with stablebronchiectasis with HRCT. They showed good correlation between the extents of bronchiecta-sis, bronchial wall thickening and mosaic attenuation and FEV1 (r5 -0.43– -0.60), FVC(r5 -0.36– -0.46), FEF25–50 (r5 -0.38– -0.57) and FEV1/FVC (r5 -0.31– -0.49). Regressionanalysis showed that extent of bronchiectasis and wall thickening were the most significantdeterminants of airflow obstruction, correlating with all PFT parameters This study also

demonstrated associations between bronchial wall thickening and clinical factors, such asexacerbation frequency and 24-hour sputum production (r5 -0.32 and -0.30). ALZEER [67] foundthat the HRCT score correlated well with FEV1 (r5 -0.51), as well as with systolic pulmonary artery pressure (P pa,sys) (r50.23), in a study of 94 bronchiectatic patients.

Studies on the utility of HRCT in the follow-up of non-CF bronchiectatic patients have beenlimited. In a study of 48 patients, SHEEHAN et al. [68] compared serial CT studies with PFTs,showing correlation of changes in PFT results with air-trapping due to mucous plugging. Greaterseverity of mucous plugging, bronchiectasis and bronchial wall thickening were predictive of decreased FEV1. In a study evaluating morphological features in bronchiectasis at baseline and2 weeks after exacerbation, SHAH et al. [27] showed that changes in HRCT score duringexacerbation of bronchiectasis also correlate with improvement in FEV1/FVC (r50.39;p50.049). Severity of bronchiectasis was the component most strongly associated with PFTresults (r50.4 for FEV1 and r50.5 for FVC), whereas tree in bud and mucous plugging were notstrongly correlated.

The validity of the use of PFTs as the gold standard in evaluating HRCT has been questioned by several authors. BRODY et al. [69] and HELBICH et al. [53] have shown that early HRCT changes,including mosaic attenuation and bronchial dilation, can be seen early in disease in the presenceof normal PFT results. LONG et al. [70] showed HRCT changes, including wall thickening andbronchial dilation in CF infants with a mean age of 2 years, further emphasising the sensitivity

of HRCT.Regular low-dose HRCT for the surveillance of CF has been adopted by several centres sincethe late 1990s [71]. This was initially in the form of 1-mm slice incremental HRCT (with 10-mm interspaces), but, more recently, of full-lung volumetric HRCT. CT is performed as early as an age of 2 years, when it is performed as controlled-ventilation CT (CVCT), requiringsedation or general anaesthesia. The rationale for using this imaging-intensive approach is thatPFT results may lag behind structural CT changes, difficulty in reliably performing PFTs in

young children and the ability of imaging to follow relevant objective structural markers, suchas bronchiectasis, bronchial wall thickening, air-trapping and mucous plugging. Furthermore,in the modern era, improved therapy has slowed the annual decline in PFT results such that

individual variability and changes due to other factors, such as technique, puberty andinfections, have made PFTs even less reliable for disease monitoring. However, the benefit hasto be viewed in the setting of radiation risk. DE JONG et al. [72] used a computational model toestimate mortality effects of regular CTs. The mean radiation dose for the published CTprotocol was 1 mSv. Survival reduction associated with annual scans from the age of 2 yearsuntil death for CF patients with a median survival of 26 and 50 years, were approximately 1 month and 2 years, respectively. Cumulative cancer mortality was approximately 2 and 13%at age 40 and 65 years, respectively. Biannual CTs exhibit half the risk. This highlights theincreasing reduction in survival with increasing age, an important point given the increasinglife expectancy of CF patients.

DE JONG et al. [73] studied 48 young patients with CF using serial low-dose HRCT and PFTs2 years apart. In all children, there was progressive structural HRCT change with deterioration inHRCT scores by 2.2–3.5% overall, but particularly with peripheral extension of bronchiectasis andmucous plugging, despite stable (or, in some cases, improved) lung function. This may reflectpoor PFT technique in young CF children, the use of predicted FEV1 (with reference to a globalpopulation) and/or the greater sensitivity of HRCT for detection of early and regional changes.

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JUDGE et al. [74] assessed serial HRCT performed 18 months apart in 39 consecutive CF patientsand found that the modified HRCT score declined faster (2.7% per year; p,0.001) than did FEV1

(2.3% per year). Six patients demonstrated worsening HRCT score with no change in PFT result.DE JONG et al. [75], in a study of 119 children and adults with CF, showed that PFT results,component and CT scores deteriorated over 2 years. The CT score (and its components) and PFTresults showed similar rates of deterioration in adults and children (p.0.09). Peripheralbronchiectasis worsened by 1.7% per year in children (p,0.0001) and by 1.5% per year in adults

(p,0.0001).

In view of the potential for discordance between morphology and function and the com-plementary nature of these variables, authors have attempted to create more-robust clinically useful composite scoring systems combining PFT results and HRCT findings [76].

Studies on assessment following therapy have been limited. R OBINSON et al. [76] used a compositescoring system using many of the HRCT parameters described above and combining them withPFT measures of obstructive function (FEV1 and FEF25–75). They showed the compositemeasurement to be more sensitive for assessing response to treatment in 25 CF children who wererandomised to a treatment arm and a nebulised saline arm; FEF 25–50 showed 13% improvement,

global HRCT 5% and composite score 30%. Small studies have shown some HRCT features to beuseful in post-treatment evaluation. NASR et al. [77] showed a significant improvement in totalHRCT score following recombinant human (rh) deoxyribonuclease (DNAse) therapy compared toplacebo. GORIS et al. [57] compared 25 CF patients with 10 age-matched controls using PFTs andautomated quantitative assessment of lung density. No significant difference was seen in PFTresults, but significant differences in air-trapping were seen, with the size of defects being the bestdiscriminator. There was a significant decrease in mean HRCT score from 25 to 22 (p50.014),with improvement in peribronchial thickening (p50.007), mucous plugging (p50.002) andoverall appearance (p50.025).

There have been some differences in the degree of correlation between PFT results and HRCTfindings of bronchiectasis in the various studies, which could be attributed to several causes,including the scoring system used, radiological interpretation, parameters assessed, populationstudied, reliability of PFTs and data analysis (multivariate versus univariate). However, the link between measures of obstructive lung function (FEV1 and FEF25–50) and bronchial wall thickness/total HRCT score has been consistently shown.

Role of HRCT in bronchiectasis

CT is invaluable in the diagnosis of bronchiectasis, but also plays an important role in theevaluation of complications and assessment and monitoring of disease severity. HRCT providesgood clinical correlation, and the use of scoring systems holds promise for monitoring of bronchiectasis. The more robust CT scoring systems have been formulated in CF patients. HRCTis sometimes of value in identifying the aetiology of bronchiectasis. Advantages of HRCT overPFTs include its ability to identify focal changes as well as provide a global score, in addition toassessing multiple parameters, some of which are reversible and others irreversible ( fig. 8).

Current British Thoracic Society guidelines recommend HRCT at diagnosis and during exacerbations,but not for routine follow-up. An exception is in bronchiectasis secondary to humoral immuno-deficiency, where follow-up HRCT may be beneficial [78].

HRCT is now widely regarded as part of the standard clinical evaluation of patients with CF. Theability to quantify extent and severity of disease and to serve as a useful outcome marker, and thepotential for assessing treatment response, make this a particularly valuable investigation.However, although HRCT provides valuable information on initial assessment, the role andperiodicity of serial imaging in CF remains controversial in view of increasing life expectancy andcumulative radiation exposure. Some authors suggest that HRCT should form part of the routinemonitoring of CF, but with due consideration to the excess radiation [71]. With appropriate

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scanning technique, it is estimated that a chest CTevery other year from birth to age 30 years wouldinvolve an effective dose of 15 mSv compared to themean background radiation dose over this period of 90 mSv [79].

Thus HRCT forms an important part of the investiga-tion and diagnosis of bronchiectasis and exacerbations.It is particularly useful in CF, where it has been shownto be a good marker of outcome and has demonstratedthe ability to pick up subtle and early changes withgreater sensitivity than PFTs.

Magnetic resonance imaging

Interest in the use of MRI for lung imaging arose inthe mid-1980s. The inherent difficulties in pulmonary MRI are well documented. Lungs have an intrinsically low proton density, which results in poor signalgeneration. This low signal is further degraded by susceptibility artefact resulting from theinnumerable air–tissue interfaces and cardiac and respiratory motion. However, the advent of parallel imaging and new rapid imaging sequences have permitted marked improvement intemporal and spatial resolution. Although spatial resolution using conventional proton MRI isless than that using CT, MRI offers significant morphological information and has advantages inenabling improved tissue characterisation and providing functional imaging, including vascularflow and respiratory mechanics. The use of novel imaging techniques, such as oxygen-enhancedMRI and hyperpolarised helium-3 MRI, potentially permits derivation of further functionalparameters, including regional ventilation, regional oxygen concentration and evaluation of lung

microstructure using the apparent diffusion coefficient (ADC).

Although application of this technique currently lies largely in the research arena, a significantadvantage of MRI is the lack of radiation, which is particularly important in patients who requirerecurrent imaging and the younger population group. This is pertinent when considering thepotential cumulative lifetime radiation dose from annual/biannual low-dose CT examination in theCF population that are currently advocated by some groups [71], especially in view of the rapidimprovement in life expectancy in this patient group, which is projected to continue. Thus it isunsurprising that much of the work on thoracic MRI imaging has been focused on patients with CF.

Conventional proton MRI features

Owing to the limited spatial resolution of MRI, assessment of bronchial wall thickness andbronchiectasis are dependent upon bronchial level, wall thickness and wall signal. Third-generation bronchi and beyond are poorly visualised on MRI, except in pathological states, whenthe wall and luminal signal are raised due to wall thickening, inflammation and mucus [80].Inflammation and oedema contribute to wall thickening. Gadolinium-enhanced images may beuseful in demonstrating inflammatory change.

Mucous plugging on MRI results in homogeneous high T2-signal intensity in proximal airways or anabnormal branching grape-like pattern more peripherally, equivalent to the tree-in-bud opacities

seen on HRCT. In contrast to CT, the improved tissue characterisation of MRI can also differentiatebetween mucus, haemorrhage and bronchial wall thickening [81]. Air–fluid levels may be identifiedon MRI, particularly in cystic or varicose bronchiectasis. Unlike CT, using contrast-enhanced MRIsequences, thickened airway walls can be differentiated from mucous plugging. Consolidation may also be identified as high T2-signal inflammatory fluid contrasts with the low airway signal,equivalent to the classical air bronchogram. Air-trapping and mosaic perfusion are not readily seenon conventional proton MRI in the absence of gadolinium (figs 9 and 10).

Figure 8. Coronal reconstruction from

high-resolution computed tomographyshowing a bronchial collateral vessel.

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An early study of 17 CF patients (aged 7–30 years) in 1995 [82] found MRI to be inferior to CT inthe assessment of bronchiectasis. Correlations between CT and MRI (r for each observer) weregood for bronchial dilation (r50.81 and 0.50), bronchial thickening (r50.82 and 0.60) andmucous plugging (r50.93 and 0.70). Progress in MRI technique in recent years has led to markedimprovement in its accuracy. In a study of six paediatric patients with CF, H EBESTREIT et al. [83]found that CXR and MRI provided equal information, and considered MRI suitable for follow-up.In a more recent study in 2007, PUDERBACH et al. [84] evaluated 31 patients with CF using CXR,MDCT and MRI. MRI and MDCT were assessed using a modified Helbich score, whereas CXR was evaluated using a modified Chrispin–Norman score. Mosaic perfusion was excluded from theoriginal scoring system as this cannot be quantified on MRI. They concluded that morphological

a) b)

Figure 9. a) Transverse magnetic resonance (T2-weighted half-Fourier acquisition single-shot turbo spin-echo (HASTE)) image and b) corresponding computed tomography image in a 14-year-old female with cystic

fibrosis. In both images, bronchial wall thickening, bronchiectasis, peripheral mucous plugging and dorsal

consolidations are demonstrated, as shown by the arrows. Reproduced from [81] with permission from thepublisher.

a) b)

Figure 10. T1-weighted magnetic resonance imaging showing appearance a) before and b) after contrast

medium in a 43-year-old cystic fibrosis patient. The post-contrast images demonstrate extensive bronchial

wall enhancement and permit differentiation of a thickened wall from intrabronchial secretions, withintrabronchial fluid having an air–fluid level (arrow). Reproduced from [81] with permission from the publisher.

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MRI showed comparable results to MDCT and CXR. Median extent scores for MRI, MDCT andCXR scores were 13, 13.5 and 14, and correlation between modalities ranged 0.63–0.80 (MRI/CT0.80, p,0.0001; MRI/CXR 0.63, p,0.0018; CXR/CT 0.75, p,0.0001). The median lobe-relatedconcordance was 80% for bronchiectasis, 77% for mucous plugging, 93% for sacculation/abscessesand 100% for collapse/consolidation.

MONTELLA et al. [85] evaluated patients with primary ciliary dyskinesia using HRCT and MRI.

They used a modified Helbich score for both HRCT and morphological MRI assessment, showingmean scores of 12 for both, good-to-excellent agreement between HRCT and MRI scores (r.0.8),and good correlation between both CT and MRI scores and FEV1 and FVC.

Functional MRI

A significant advantage of MRI over CT is its superior ability to assess function. Within the lungsthis mainly involves evaluation of haemodynamic function and perfusion and ventilation studies.

Perfusion imaging

In the presence of small airways obstruction, regional ventilation defects lead to impaired gasexchange and reflex hypoxic vasoconstriction [86]. Perfusion imaging can thus serve as a markerof airway obstruction. ITTI et al. [87] used radionuclide imaging to show that the degree of abnormal lung perfusion correlates well with disease severity in CF, as measured by PFTs and theShwachman radiographic score. Contrast-enhanced pulmonary MRI imaging can be used toacquire a 3D data set in just 1.5 seconds [88, 89]. This also has advantages over scintigraphy interms of radiation dose and provides regional information.

EICHINGER et al. [90] performed morphological and contrast-enhanced MRI sequences on 11patients with CF; 198 lung segments were scored for morphological (3 point score of none,

moderate or severe) and perfusion defects (0 normal; 1 impaired perfusion). In 86% of segmentsconsidered morphologically normal, homogenous perfusion was demonstrated, whereas 97% of segments with severe morphological changes were associated with perfusion defects. Of segmentswith moderate morphological changes, 53%showed normal and 47% impaired perfusion. Thuscontrast-enhanced MRI appears to be a feasible method of assessing regional perfusion defects as asurrogate for small airways disease, although further work is required in order to improvesensitivity in moderately affected areas of lung.

In bronchiectasis, increased blood flow though bronchial and nonbronchial systemic collateralvessels results in a systemic arterial to pulmonary venous shunt. Using conventional proton MRIand phase-contrast flow-sensitive sequences, aortic and pulmonary arterial flow can be readily

quantified. In a study of 10 patients with CF and 15 healthy volunteers, LEY et al. [91] found asignificantly increased shunt in CF patients (1.3 L?min-1) compared to healthy volunteers(0.1 L?min-1).

Oxygen-enhanced MRI exploits the weak paramagnetic properties of oxygen, which cause ashortening of T1 at high concentration and can be used as a gaseous contrast agent. The solubility of oxygen means that images represent a combination of ventilation and perfusion. A limitation isthe low signal-to-noise ratio [81]. JAKOB et al. [92] studied five CF patients and five healthy volunteers using oxygen-enhanced MRI, showing inhomogeneity of the lung parenchyma in theCF patients.

Hyperpolarised noble-gas-enhanced MRI

Imaging of hyperpolarised noble gases using MRI is a relatively new imaging technique that showspromise in the research arena in the evaluation of several ventilatory functional parameters.Hyperpolarised helium-3 and hyperpolarised xenon-129 are gaseous contrast agents that provide avery high MR signal [35]. Since oxygen promotes depolarisation, the polarised helium-3 is mixed

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with nitrogen rather than air before being administered by active inhalation via a device such as aplastic Tedlar bag or respirator-driven gas delivery system. The bag method uses a mixture of 300 mL helium-3 and 700 mL nitrogen and requires a single anoxic breathhold. The respirator-driven system provides an accurate single dose followed by an air chaser and hence no anoxicbreathhold is required.

Polarisation is not renewable and has to be used carefully during the scan, with use of sequences to

maximise use of finite magnetisation [93]. Dedicated receiver coils for the relevant resonancefrequency of helium-3 and xenon-129 are also required.

The different physical properties of helium-3 and xenon-129 present different opportunities.Although helium-3 provides a better signal and greater polarisation levels have been obtained, itslarger diffusion coefficient results in signal loss. In addition, although helium-3 is virtually insoluble in water, xenon-129 is highly soluble and hence has potential for use in assessingperfusion [93]. On a purely practical basis, the limited supply of helium-3, estimated at 200 kgglobally [94], compared to that of xenon-129 is likely to lead to xenon-129 eventually emerging asagent of choice [95].

The main techniques used in hyperpolarised noble gas imaging are static ventilation imaging anddynamic ventilation imaging, as well as assessment of lung microstructure using ADC and regionaloxygen tension imaging.

MCMAHON et al. [96] showed that static helium-3 MRI ventilation in CF correlated strongly with HRCT assessment of structural abnormalities (R 5¡0.89; p,0.001), and that thecorrelation was higher between helium-3 MRI and PFT results than helium-3 MRI and HRCT.In a further observational study of 18 patients aged 5–17 years with CF undergoinghyperpolarised helium-2 MRI, VAN BEEK et al. [97] confirmed moderate correlation between avisual score of ventilation on MRI and global assessment of pulmonary function (FEV1 r5 -0.41

and FVC r5

-0.42).In a study comparing healthy volunteers and CF patients, MENTORE et al. [98] performedspirometry and hyperpolarised helium-3 imaging at baseline in all cases, and following variousinterventions in the eight CF patients. Treatments in the CF group included bronchodilators,DNAse and chest physiotherapy. The number of ventilation defects was scored. The helium-3ventilation score correlated moderately with spirometry, and was higher in CF patients thancontrols (mean 8.2 and 1.6, respectively). The helium-3 ventilation score was raised in comparisonto controls even in CF patients with normal spirometric results. Defects in the eight treatedpatients decreased in response to bronchodilator therapy (p50.025). WOODHOUSE et al. [99]demonstrated reproducibility of regional and total lung volume measurements using hyper-polarised helium-3 MR in two examinations performed 30 minutes apart in a group of five youngCF sufferers.

The ADC of helium-3 or xenon-129 in the lung and the paramagnetic effect of oxygen are twonovel methods with the potential for extracting clinically relevant data. The ADC provides ameasure of the diffusion of gas and thus an assessment of the degree to which free diffusion isrestricted. Helium-3 has a very high self-diffusion coefficient, but, in the lung, diffusion becomesrestricted by the boundaries of the airspaces, and thus the ADC can be used to interrogate themicrostructure of the lung [93].

The oxygen-induced depolarisation of helium-3 or xenon-129 results in signal decay proportionalto the concentration of oxygen [100], permitting estimation of regional oxygen concentration anduptake and regional pulmonary perfusion, and providing a regional ventilation/perfusion (V /Q )map at a much higher resolution than that of radionuclide imaging [101]. PATZ et al. [95]measured regional oxygen concentrations using xenon-129, and, although this is inherently morecomplex than with helium-3 due to diffusion into septal tissue and vasculature, an oxygen tension(P O2) equivalent can be calculated, which can provide valuable functional information.

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A limitation of hyperpolarised noble gas MRI is that the signal is also influenced by factors otherthan ventilation, including the sensitivity of the MR coil and local oxygen concentration in thelung. The need for noble gas isotopes and both polarisation hardware and additional MRIhardware, together with considerable physical and technical support, mean that hyperpolarisednoble gas imaging remains expensive and limited to the research environment. However, thepotential to perform noninvasive evaluation of regional ventilation, diffusion, regional oxygenconcentration, lung microstructure and perfusion without the use of ionising radiation has

potential, especially in the research setting.

Summary

MRI has potential in the imaging of bronchiectasis, particularly in conditions such as CF, in which young patients may require serial imaging for disease monitoring and assessment of response totreatment. Compared to HRCT, the ability of MR to provide functional imaging and lack of radiation could compensate for its limited spatial resolution. With improvement in MRItechniques, recent studies have shown good reproducibility and good correlation with PFT results.Further work is required to improve spatial resolution, develop robust validated scoring systems

and evaluate correlations with clinical outcomes.

Currently cost, limited availability and limited spatial resolution limit the use of MRI inbronchiectasis largely to the research arena. Although hyperpolarised noble gas imaging has greatpotential in terms of provision of functional data, technical issues and set-up and ongoing costssuggest its role will be limited to research for the foreseeable future.

Scintigraphy

Prior to the advent of HRCT, ventilation (with or without perfusion) scintigraphy was used to aid

disease evaluation in bronchiectasis. DOLLERY and HUGH-JONES [102] studied the physiologicalimplications of bronchiectasis and found reduced blood flow and impaired ventilation in bronchiectaticareas. V /Q scintigraphy typically demonstrates matched ventilation and perfusion defects, reflectingabnormal ventilation secondary to bronchiectasis and associated small airways obstruction [103].

PIFFERI et al. [104] studied 16 children aged 4–18 years with clinical and CXR evidence of bronchiectasis, performing HRCT and V /Q scintigraphy. The extent of bronchiectasis, degree of air-trapping on expiratory HRCT and ventilation and perfusion scores from V /Q scintigraphy were assessed. HRCT scores for bronchiectasis and air-trapping showed a strong correlation withperfusion (r50.82; p,0.001) and ventilation scores (r50.72; p,0.01). There was a moderatenegative correlation between FEV1 and HRCT bronchiectatic scores (r5 -0.53; p50.02), air-

trapping (r5 -0.64; p50.007) and atelectatic score (r5 -0.54; p50.03).

The authors concluded that HRCT provides a comprehensive assessment of children withbronchiectasis, and V /Q scintigraphy and lung function are additive tools to aid diagnosis andguide therapeutic management. The ongoing issue of radiation dose and absence of usefulanatomical information, however, limit the value of V /Q scintigraphy in routine practice.

Mucociliary clearance

The interaction between the cilia on respiratory epithelium and the periciliary mucous layer

(periciliary liquid (PCL))/overlying mucous layer, together known as the airway surface liquid(ASL) layer, has been widely investigated. Coordinated function is responsible for the constantclearance of foreign material, including microorganisms and other debris, towards the pharynx and ultimate expectoration or swallowing. Impaired mucociliary function has been implicated inmany disease processes, but particularly bronchiectasis. Techniques to objectively measuremucociliary clearance (MCC) in vivo have been sought in order to improve understanding of thedisease processes and evaluate therapeutic response.

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Techniques for measuring MCC

In vivo assessment of MCC relies on the inhalation of radiolabelled particulate material thatbecomes trapped in the mucous layer and can be imaged scintigraphically. Data acquired from thegamma camera over time can be presented either as a series of images for visual inspection or,more commonly, as time–activity curves (fig. 11).

Technetium-99m-labelled human albumin, iron oxide and technetium-99–sulfur colloid are someof the aerosols used. Sulfur colloid is nondiffusible, remains extravascular and is expelled by MCC/swallowing. Deposition of particles is affected by many factors. Some, such as particle size andbreathing pattern, can be controlled for, whereas others reflect the underlying lung condition ( e.g.obstruction and lung size). Thus, in order to make comparisons, it is important to standardise thenature of the aerosolised particles (size and distribution) and provide a consistent nebulised flow in order to produce a reproducible deposition rate [105].

In order to define the margins of the lung and differentiate central (C) and peripheral (P) lungregions, an initial ventilation study utilising a xenon-133 or krypton-81 scan [106] can beperformed immediately prior to administration of particulate material. Following this, the patient

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Figure 11. Measurement of mucociliary clearance (MCC). a) A xenon-133 equilibrium scan was used to identifythe left (L) and right (R) lung boundaries in a normal subject, and assign central (C) and peripheral (P) regions of

interest (b). c) Deposition image obtained immediately after inhalation of technetium–sulfur colloid in the samesubject. d) Mean rate of clearance of technetium–sulfur colloid from 12 subjects with cystic fibrosis at baseline(&) and immediately after inhalation of hypertonic saline ($) [16]. The fast phase (approximately 0–20 minutes;

– – – – –), reflecting clearance from large airways, and slow phase (from 40 minutes to start of cough clearance

measurement; --------), reflecting smaller airway clearance, are highlighted. e) Effect of ratio of radioactive countsmeasured in the C and P regions on rate of MCC, as denoted by particle retention at 120 minutes, in a cohort of

normal study subjects. VC: voluntary cough. Reproduced from [105] with permission from the publisher.

h

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inhales nebulised radiolabelled aerosol. Various adjuncts are used during nebulisation in order toprovide consistent reproducible dosing, including pneumotachographic devices with visualfeedback to control inhalation flow rate and tidal volume within specific ranges, metronomes toguide the timing of inhalation and exhalation, and aerosol dosimetric equipment to pulse aerosoldelivery during specific portions of the breathing cycle [105].

Following inhalation, the patient is positioned in front of the gamma camera and the gamma

radiation emitted is detected and recorded. The results are analysed graphically with reference tothe zones defined on the initial ventilation scan. At this stage of analysis, it is important to accountfor decay of radioisotope and background radiation level. Given the variability of deposition of radiolabelled aerosol in various parts of the airways, it is important to measure the initialdeposition pattern. The deposition pattern is usually presented as a ratio between C and P or as thepenetration index (PI), which is the ratio of radioactive counts per pixel in P to counts per pixel inC [107]. A high initial C/P deposition ratio or low PI is associated with a higher clearance rate inthe central airways, making this a potential confounding factor in analysing final clearance data.

The rate of clearance from central airways is up to 100–1,000 times faster than that fromperipheral airways [108, 109]. A two-phase MCC pattern is typically seen, with an initial rapid

phase lasting approximately 30 minutes and reflecting clearance from the central airways and aprolonged slower phase. The latter occurs over 1–2 hours and is thought to represent movementof particles to compartments that are more difficult to clear (e.g. absorption of PCL) or slow clearance from peripheral airway/alveolar deposition. 24-hour measurement of clearance has alsobeen used to assess the pattern of clearance during the slower phase, which could also be of valuein assessing response to treatment. This, however, requires a higher administered radiation dosedue to the 6-hour half-life of technetium. A static measurement at 24 hours can be used as amarker of deposition in the nonciliate airways or alveoli [110]. The relative contributions to the24-hour measurement of slow clearance from peripheral airways, alveolar deposition and mixingin a poorly cleared part of the ASL, are not fully understood [105]. The static 24-hour

measurement is useful in aiding calculation of other parameters, such as the tracheobronchialretention (TBR) curve, which is derived by subtracting the 24-hour retention from the correctedlung retention (LR) curve.

A potentially more accurate means of assessing peripheral clearance is inhaling particles of different sizes, smaller (4 mm) particles being deposited more peripherally than larger (7.5 mm)ones [111]. YEATES et al. [108] proposed labelling the differently sized aerosolised particles withdifferent radioisotopes to permit simultaneous measurement of central and peripheral regionalclearance. This method is not widely used due to practical difficulties.

Some authors [106] advocate measurement of activity solely in the lung periphery, where uptake

is more homogenous. This avoids the potential errors caused by differential uptake in central andperipheral airways and confounding by variability of initial deposition. It is, however, limited by a low signal-to-noise ratio due to lower deposition peripherally and intrinsically slower clearancein these regions. It is also not possible to assess response to therapy in the central airways usingthis method.

Additional imaging following various interventions, such as cough clearance (CC) assessed aftera standardised pattern of coughing, can also be performed. This has some limitations, asperforming this late in the study makes it less sensitive as the central airways would have beenlargely cleared of radioisotope. A further normalisation measurement of C/P ratio must beperformed prior to CC.

Clinical applications

Measurement of MCC has important research applications in both understanding diseaseprocesses and assessing therapeutic response. To date, the technique has not been broadly adoptedclinically, being cumbersome to establish.

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Disorders that impair MCC can seriously affect respiratory function, with build-up of thick mucus in the airways/lungs and inability to expel harmful material. This can predis-pose to complications, such as infection and structural lung disease. Other factors may influenceMCC, which is faster in nonsmokers and enhanced by b2-agonists, particularly in non-smokers [112].

CF is a prominent example of a condition in which measurement of MCC could prove useful.

Scintigraphic evaluation has also been used to demonstrate impaired MCC in primary ciliary dyskinesia [110] and following lung transplantation [113]. There have been limited studies inidiopathic bronchiectasis [114].

In CF, disordered ion transport leads to dehydration of the ASL layer [115], impaired ciliary motion and decreased mucus clearance, ultimately leading to degradation of cilia [105],exacerbating the cycle of frequent infections. Ongoing research is focused on the earliest stages of disease pathogenesis and therapeutic interventions to target defective mucus clearance.Biomarkers objectively measuring MCC have the potential to assess response to treatment atan early stage in contrast to longer-term end-points, such as clinical or functional parameters,and thus to expedite drug development.

In a study of 24 patients with CF, DONALDSON et al. [116] showed improved MCC, measured usingtechnetium-99-labelled iron oxide, at both 1 and 24 hours after inhalation of hypertonic saline,and that pretreatment with amiloride reduced the magnitude of this improvement. Usingradiolabelled iron oxide BENNETT et al. [106] demonstrated significantly reduced baseline MCC at40 minutes in CF patients compared to healthy volunteers. In the CF group, treatment withuridine 5’-triphosphate and amiloride in combination improved peripheral MCC to near-normallevels. Similar studies have used technetium–sulfur colloid to demonstrate improved MCC and CCfollowing inhaled hypertonic saline and mannitol in CF patients [117].

In summary, MCC can be measured using radiolabelled particulate materials, such as technetium-

99–sulfur colloid. In the research setting, this provides a potential biomarker for evaluation of mucociliary dysfunction and, in particular, assessment of the impact of targeted therapies. This isespecially true in conditions such as CF, in which impaired MCC plays a significant part in thepathophysiology of the disease and where treatment is targeted at improving this.

Conclusions

Imaging plays a central role in the diagnosis, characterisation and quantification of disease severity in bronchiectasis, as well as the evaluation of complications. Currently CXR and CT are the mainmodalities. CXR is the initial screening tool, but has well-documented limitations in sensitivity

and specificity, particularly in early disease. Radiography also plays an important role in thediagnosis of complications. HRCT is the reference standard in identifying airway dilation,permitting detection of disease and quantification of extent. Routine surveillance CT has potentialfor the diagnosis of structural disease at an early stage and impact on patient care, particularly where these is discordance with functional parameters. Radiation dose, however, remains anarea of concern requiring further elucidation, particularly in the cohort of CF patients given theirever-increasing life expectancy and the potentially large cumulative radiation dose. Although thepresent review concentrates on the monitoring of disease, CT is an excellent problem-solving tool,permitting the diagnosis of both infective complications, such as abscess, empyema andaspergilloma, as well as identification of small pneumothoraces or enlarged systemic collateral

vessels (fig. 11) and aiding relevant image-guided intervention.

MRI offers opportunities to image the lung structure and its function without the use of ionisingradiation. The spatial resolution is inferior to that of CT but has improved substantially overrecent years. An increasing role for structural (proton) MRI is anticipated, but widespreadadoption will require further evidence to support its effectiveness. Although hyperpolarised noblegases permit interrogation of a range of physiological parameters, the set-up costs of this technique

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are likely to ensure it remains a predominantly research tool for at least the foreseeable future.Evaluation of MCC using scintigraphy is another area in which there is great potential, particularly in order to expedite and reduce costs of drug development.


None declared.

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106. Bennett WD, Olivier KN, Zeman KL, et al. Effect of uridine 5’-triphosphate plus amiloride on mucociliary

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107. Robinson M, Eberl S, Tomlinson C, et al. Regional mucociliary clearance in patients with cystic fibrosis. J Aerosol Med 2000; 13: 73–86.

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109. Wilkey DD, Lee PS, Hass FJ, et al. Mucociliary clearance of deposited particles from the human lung: intra- and

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110. Marthin JK, Mortensen J, Pressler T, et al. Pulmonary radioaerosol mucociliary clearance in diagnosis of primary

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Suppl. 127, 41–56.

112. Mortensen J, Lange P, Nyboe J, et al. Lung mucociliary clearance. Eur J Nucl Med 1994; 21: 953–961.

113. Laube BL, Karmazyn YJ, Orens JB, et al. Albuterol improves impaired mucociliary clearance after lungtransplantation. J Heart Lung Transplant 2007; 26: 138–144.

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116. Donaldson SH, Bennett WD, Zeman KL, et al. Mucus clearance and lung function in cystic fibrosis with

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117. Robinson M, Daviskas E, Eberl S, et al. The effect of inhaled mannitol on bronchial mucus clearance in cystic

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Chapter 6

Microbiology of non-

CF bronchiectasis J.E. Foweraker* and D. Wat #

Summary

Non-cystic fibrosis (CF) bronchiectasis is a complex disorder

characterised by recurrent chest infections and poorly regulatedrespiratory innate and adaptive immunity. These lead to a‘‘vicious cycle’’ of impaired mucociliary clearance, chronicinfection, bronchial inflammation and progressive lung injury.The most prevalent pathogenic bacteria are Haemophilusinfluenzae , Pseudomonas aeruginosa, Streptococcus pneumoniae ,Staphylococcus aureus and Moraxella catarrhalis although

variations in sampling techniques and detection methods haveinfluenced their isolation rates. These organisms can inhibit

mucociliary clearance, destroy respiratory epithelium andproduce biofilms that promote persistent infection by blocking innate immune defences and increasing antibiotic resistance.While numerous studies have examined the role of differentbacteria in CF and chronic obstructive pulmonary disease, littleis known about how they contribute to the pathogenesis of non-CF bronchiectasis. There is also a paucity of data regarding therole of respiratory viruses in this condition. This chapterdescribes the microbiology of non-CF bronchiectasis, definesthe bacterial mechanisms that may contribute to persistentinfection and airway damage and discusses the potential role forrespiratory viruses in this condition. Understanding thepathogenic properties of these microorganisms may allow thedevelopment of novel therapies for the management of respiratory exacerbations.

Keywords: Anaerobes, Haemophilus, Moraxella, Pseudomonas,Streptococcus, viruses

*Dept of Microbiology, and#Lung Defence Unit, Papworth

Hospital, Cambridge, UK.

Correspondence: J.E. Foweraker,Dept of Microbiology, PapworthHospital, Papworth Everard,Cambridge, CB23 3RE, UK, Email

[email protected]


Patients with bronchiectasis are commonly colonised with potentially pathogenic microorgan-isms in the airways [1]. These microorganisms can cause lung infections and may produce a

number of inflammatory mediators that can lead to progressive tissue damage and bronchialobstruction. The phenomenon of chronic infection, bronchial inflammation and progressive lunginjury is a ‘‘vicious cycle’’ and is also the reason why prompt evaluation of infection is important [2].

6 8

M I C R O B I O L O G Y



Being able to identify the causative bacterium may allow appropriate antibiotic administration tobreak this vicious cycle.

The most prevalent microorganisms found in non-cystic fibrosis (CF) bronchiectasis are discussedin this chapter and we have included the role of viruses, as well as some recent studies that haveinvestigated microorganisms that are not usually considered to be pathogens in the respiratory tract. Surprisingly, there is little published data on the epidemiology and pathogenesis of infections

in non-CF bronchiectasis. However, there are similarities with infections in CF bronchiectasis andchronic obstructive pulmonary disease (COPD). Where the literature for non-CF bronchiectasis issparse, studies in CF and COPD have been drawn upon as these may aid the understanding of themicrobiology; in particular the adaptations that take place to enable microorganisms to establishand maintain chronic infection and the role taken in the development of exacerbations.

Fungal infections, including allergic bronchopulmonary aspergillosis (ABPA), are discussed furtherby HILVERLING et al . [3], while nontuberculous mycobacteria infections are discussed further by DALEY [4] in this Monograph.

Range of bacteria in patients with non-CF bronchiectasisSeveral studies have reviewed the bacteria found in patients with non-CF bronchiectasis (table 1).A similar range of organisms is found in most studies, but the prevalence of each varies. Age,ethnicity, the underlying causes of bronchiectasis and the proportion of patients that were stableor had cultures taken during an exacerbation varies between the different studies and would beexpected to affect the microbial flora found. The pattern of antibiotic usage, including long-termprophylaxis, may vary between different centres and could also have an affect on the type of microorganisms cultured. The type of respiratory specimen tested may also determine the rate of positive cultures found. The use of a protected specimen brush to take samples at bronchoscopy

yielded the highest positivity rate when compared with sputum specimens in one study [7]. Finally

the methodology used for analysis (quantification, culture and identification techniques) will vary between centres and could also affect the result.

Haemophilus influenzae and Pseudomonas aeruginosa were the most common bacteria found in themajority of the studies and the most likely to cause long-term colonisation [12]. No potentially pathogenic microorganisms were cultured from 18–24% of the patients investigated and anabsence of a potentially pathogenic microorganism was associated with the milder disease [9, 13].

Haemophilus influenzae

H. influenzae has been reported in 14–52% of patients with non-CF bronchiectasis. It is a Gram-negative coccobacillus with specific growth requirements, which can be difficult to isolate in thelaboratory if mixed with other flora. Some H. influenzae possess a polysaccharide capsule and canbe typed using type-specific anticapsule antisera. Those with the type B capsule (Hib) can causeinvasive infection with bacteraemia, and are most familiar as a cause of meningitis or epiglottitis.The use of Hib vaccine has greatly reduced the incidence of these life-threatening conditions.H. influenzae with capsule types other than type B are relatively rare and are far less pathogenic.The nonencapsulated strains, referred to as nontypeable H. influenzae (NTHi), are also lesspathogenic than Hib and only rarely cause bacteraemia. They live as commensals in the humanupper respiratory tract but can cause otitis media, sinusitis and conjunctivitis, often following a

primary viral infection. NTHi are a common cause of lower respiratory infection in patients withunderlying respiratory abnormalities including non-CF bronchiectasis [9]. The Hib vaccine doesnot prevent infection with NTHi as it only contains the H. influenzae type B capsule antigen.

NTHi could be an oral contaminant in expectorated sputum; however, studies using a protectedspecimen brush (PSB) at bronchoscopy found NTHi in significant numbers in non-CFbronchiectasis, confirming its presence in the lower respiratory tract [7]. In contrast

6 9

J . E . F O W E R A K E R A N D D

. W A T



Haemophilus parainfluenzae , a com-mon commensal organism found inthe upper respiratory tract, may becultured from sputum but was notfound in PSB samples. In patientswith COPD the presence of NTHi insputum was associated with raised

inflammatory cytokines, whereas pa-tients with H. parainfluenzae in spu-tum had similar levels of cytokines tothose who had no microorganismscultured from their sputum, suggest-ing that even if present in the lowertract it does not have a direct patho-genic role [14, 15].

There is little published data on theepidemiology of H. influenzae innon-CF bronchiectasis. It may becultured repeatedly from the samepatient over several years, but with-out typing data it is not known if this is the persistence of a singlestrain or repeated episodes of infec-tion [9]. In COPD patients, NTHiwere found in higher numbers (.106

colony forming units (CFU)?mL-1)during exacerbation compared with

when the patient was stable, andexacerbations in COPD may be as-sociated with the appearance of a new strain [16, 17]. A prospective study inCOPD using molecular typing of H. influenzae and direct analysis of amplified DNA from sputum showedpersistence of the same strain overprolonged periods [18]. This suggestseither long-term colonising infection

in the lung or persistence in theupper respiratory tract with repeateddeposition followed by clearance fromthe lung. In CF, sequential infectionwith different strains of H. influenzae was found in some patients and per-sistence of the same clone in otherindividuals [19].

NTHi have various properties that

can help explain their pathogenicity and ability to persist in the lung. They can adhere to mucus and to variouscell types in the human respiratory tract using pili and other adhesionmolecules. Virulence factors includethe endotoxin lipo-oligosaccharides

T a b l e 1 .

R a n g e

o f m i c r o o r g a n i s m s c u l t u r e d f r o m

p a t i e n t s w i t h n o n - c y s t i c f i b r o s i s b r o n c h i e c t a s i s

F i r s t a u t h o r

[ r e f . ]

C

o u n t r y

S u b j e c t s

n

S a m p l e

A g

e y r s

S t a b l e o r a t

e x a c e r b a t i o n

P a t i e n t s w i t h o r g a n i s

m s c u l t u r e d f r o m

r e s p i r a t o r y t r a c t #

H a e m o p h i l u s

i n f l u e n z a e

P s e u d o m o n a s

a e r u g i n o s a

S t r e p t o c o c c u s

p n e u m o n i a e

M o r a x e l l a

c a t a r r h a l i s

S t a p h y l o c o c c u s

a u r e u s

R T F l o r a /

n o P P M

O t h e r

Z A I D [ 5 ]

I r e l a n d

9 2

S p u t u m

,

1 8

N D

5 0 ( 4 6 )

8 ( 9 )

3 4 ( 3 7 )

9 ( 1 0 )

1 4 ( 1 5 )

N D

P A L W A T W I C H A I [ 6 ]

T h a i l a n d

5 0

S p u t u m

5 8 (

3 0 – 8 5 )

N D

7 ( 1 4 )

1 0 ( 2 0 )

3 ( 6 )

2 ( 4 )

9 ( 1 8 ) R T F l o r a

7 ( 1 4 ) K . p n e u m o n i a

7 ( 1 4 ) G N B

2 ( 4 ) G P B

A N G R I L L [ 7 ]

S p a i n

7 5

P S B

5 8 (

1 6 – 7 6 )

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1 2 ( 1 6 )

6 ( 8 )

3 ( 4 )

2 ( 3 )

1 8 ( 2 4 ) R T

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1 ( 1 ) A . x y l o s o x i d a n s

1 ( 1 ) E . c o l i

N I C O T R A [ 8 ]

U S A

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¡ 1 6 . 7

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3 7 ( 3 0 )

3 8 ( 3 1 )

1 3 ( 1 1 )

3 ( 2 )

9 ( 7 )

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1 6 ( 1 3 ) G N B

2 ( 3 ) A n a e r o b e s

K I N G [ 9 ]

A u s t r a l i a

8 9

S p u t u m

5 7

¡ 1 4

S t a b l e

4 2 ( 4 7 )

1 1 ( 1 2 )

6 ( 7 )

7 ( 8 )

3 ( 4 )

1 9 ( 2 1 ) n o

P P M

2 ( 2 ) E . c o l i

1 ( 1 ) A . x y l o s o x i d a n s

P A S T E U R [ 1 0 ]

U K

1 5 0

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5 2 ( 3 5 )

4 6 ( 3 1 )

2 0 ( 1 3 )

3 0 ( 2 0 )

2 1 ( 1 4 )

N D

M A C F A R L A N E [ 1 1 ]

U K

1 4 3

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6

0 . 6

( 1 6

– 9 0 )

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C o l o n i s e d

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7 5 ( 5 2 )

6 2 ( 4 3 )

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3 9 ( 2 7 )

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)

1 2 ( 8 ) S . m a l t o p h i l i a

4 ( 3 ) A . x y l o s o x i d a n s

4 2 ( 3 0 ) C o l i f o r m s

4 7 ( 3 3 )

4 7 ( 3 3 )

1 3 ( 9 )

9 ( 6 )

1 5 ( 1 0 )

2 ( 1 ) S . m a l t o p h i l i a

2 ( 1 ) A . x y l o s o x i d a n s

1 3 ( 9 ) C o l i f o r m s

D a t a a r e p r e s e n t e d a s m e a n ( r a n g e ) , m e a n ¡ S D

o r n ( % ) , u n l e s

s o t h e r w i s e s t a t e d .

R T F l o r a : u p p e r r e s p i r a t o r y t r a c t f l o r a ; P P M : p o t e n t i a l l y p a t h o g e n i c m i c r o o r g a n i s m s ; N D : n o t d e s c r i b e d ; K . p n e u m o n i a e : K l e b s i e l l a

p n e u m o n i a e ; G N B : G

r a m - n e g a t i v e b a c i l l i ; G P B : G r a m - p o s i t i v e b a c i l l i ; P S B : p r o t e c t e d s p e c i m e n b r u s h ; A . x y l o s o x i d a n s : A c h r o m o b a c t e r x y l o s

o x i d a n s : E . c o l i : E s c h e r i c h i a c o l i ; S . m a l t o p h i l i a : S t e n o t r o p h o m o n a s

m a l t o p h i l i a ;

# : s o m e h

a d m o r e t h a n o n e P P M

c u l t u r e d ; " : b a c

t e r i a w e r e i s o l a t e d o n a t l e a s t t w o o c c a

s i o n s ,

3 m o n t h s a p a r t , i n 1 y e a r .

7 0




(LOS), and immunoglobulin (Ig)-A protease [20]. NTHi possess mechanisms to vary the structureand activity of LOS and these may explain variations in the pathogenicity of different isolates [21].Studies comparing the proteome of H. influenzae grown in vitro, either in pooled sputum orchemically defined media, have shown that the organism is able to adapt to oxidative stress andlimited nutrients [22]. This is thought to be because H. influenzae has the ability to generate a diversepopulation that allows rapid adaptation to changes in the environment by expansion of the clonalmembers that express the phenotypic characteristics needed to survive. Mechanisms used by H.

influenzae to generate phenotypic diversity include altered gene expression, e.g. by phase variation,and altered gene content by mutation or by horizontal gene transfer, e.g. direct DNA uptake-transformation, or via bacteriophage [23].

NTHi may be able to evade the immune response by varying its surface antigens. Mechanismsinclude phase variation of LOS [24], and changes to outer membrane proteins (OMP) either by horizontal gene transfer or point mutations of the immuno-dominant OMP, i.e. P2. Antigenicdrift, resulting from change in the P2 gene, has been observed in persistent infections in patientswith COPD [25]. NTHi could be protected within host cells as they have been found insidemacrophages in the chinchilla otitis media model and in macrophage-like cells in humanadenoids. NTHi were able to enter cultured nonciliated respiratory epithelial cells and cross therespiratory epithelium [26]. Using in situ hybridisation, NTHi were identified inside cells inbronchial biopsies taken from patients with COPD [27].

H. influenzae (along with other bacteria infecting a bronchiectatic lung) may exist in biofilms in therespiratory tract. These are co-operative populations of bacteria surrounded by an amorphous matrix and could help the organism to survive in a hostile environment by resisting both host defences andantibiotics. The antibiotic resistance observed for bacteria growing in biofilms is in part attributable toits electrolyte content but also by reduced bacterial growth or even dormancy within the biofilmmatrix. NTHi from patients with COPD can form biofilms in vitro , and NTHi biofilms were seen inthe chinchilla model of otitis media [28, 29]. NTHi cultured from CF patients could form biofilms in

vitro and on the surface of cultured airway epithelial cells. Structures consistent with biofilmscontaining H. influenzae were also found in bronchoalveolar lavage (BAL) samples from children withCF [30]. NTHi in biofilms were more resistant to antibiotics in vitro . Sub-inhibitory concentrations of azithromycin were found to reduce the size of both growing and established biofilms [31].

The prevalence of antibiotic resistant NTHi increases over time in patients with non-CFbronchiectasis [9]. Many are resistant to amidopenicillins (e.g. amoxicillin, ampicillin) either dueto production of b-lactamase or alteration of penicillin binding proteins. Quinolone resistance isnow recognised and resistance rates to trimethoprim and tetracycline are rising.

Antibiotic resistance may occur by horizontal transfer of genetic material from other organisms in thecomplex polymicrobial environment of the mouth and upper respiratory tract. It may also take placein the lower respiratory tract, which may be polymicrobial in non-CF bronchiectasis. Alternatively,resistance may result from gene mutation. Some NTHi have a higher than usual mutation rate due toa mutation in mutS , which is one of the methyl-directed mismatch repair genes (MMR) that correctserrors in DNA. This hypermutability is not usually thought to be advantageous, as many randommutations can reduce bacterial fitness. However, if mutations lead to antibiotic resistance, thehypermutable state may become beneficial to the bacterial population. Hypermutators are generally rare in acute infection but hypermutable H. influenzae have been found in patients with CF and thesestrains have more resistance to antibiotics compared with normo-mutators [19, 32]. Hypermutability is seen in other species causing chronic infection (as is discussed later in this chapter) and may be ageneral adaptation to long-term survival in the lung. The prevalence and role of hypermutable

H. influenzae in non-CF bronchiectasis has yet to be assessed.

Pseudomonas aeruginosa

P. aeruginosa is a versatile nonfermentative Gram-negative bacillus that is found in a range of environments. It is an opportunistic human pathogen that can cause severe, acute and invasive

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infections, such as necrotising ventilator-associated pneumonia and infections in immuno-compromised patients often with bacteraemia [33]. It is one of the most common causes of infection in non-CF bronchiectasis and other chronic lung diseases, most notably CF, but may alsobe important in severe COPD. The epidemiology of P. aeruginosa , the mechanisms of pathogenicity and the genotypic and phenotypic changes in chronic infection have beenextensively studied in CF, with fewer publications in non-CF bronchiectasis and COPD. There aremany similarities between the infections in these different conditions, suggesting a common route

of adaptation to chronic infection in the lung.

P. aeruginosa in CF

Early infections in CF are caused by genotypically distinct isolates, suggesting repeated episodes of acquisition. These early P. aeruginosa have the typical phenotype of isolates causing acuteinfections and environmental strains [34]. As chronic infection with P. aeruginosa can lead to anaccelerated deterioration in lung function, antibiotic treatment regimens were developed to clearearly infection and delay the onset of chronic infection [35]. CF patients eventually developed apersistent infection that seldom cleared despite aggressive antibiotic therapy. While there are some

mixed infections, most CF patients carry a single genotype of P. aeruginosa , often for many decades [36, 37], and exacerbations do not appear to be due to the acquisition of a new strain of P. aeruginosa [38]. Early studies in CF showed that individual patients were infected with distinctstrains that were thought to have been acquired from the environment. Some siblings sharedstrains but it was not known whether this was cross-infection or exposure to a commonenvironmental source. More recently there have been reports in several countries of cross-infection between CF patients with what are termed ‘‘epidemic’’ strains. Some, in particular theLiverpool epidemic strain (LES), have been associated with increased morbidity [39, 40]. LES isnow the most common epidemic strain in the UK affecting as many as 11% of patients in Englandand Wales [41].

P. aeruginosa in COPD

P. aeruginosa has been cultured from 4–15% of patients with COPD and was more prevalent inpatients with advanced disease, particularly those requiring mechanical ventilation for severeexacerbations. P. aeruginosa infection was associated with steroid use, prior antibiotics and a low forced expiratory volume in 1 second (FEV1) [42]. In a study of 126 patients with moderate-to-severe COPD over an 11-year period, 39 patients grew P. aeruginosa from one or more sputumculture. There was a significant association with the culture of a new strain of P. aeruginosa andsymptoms of an exacerbation. However, of interest, two-thirds of new infections that latercleared from the sputum, did so without the use of specific antibiotic treatment [43]. Only 13 patients had carriage of the same clone for more than 6 months with four patients infectedwith mucoid strains. Chronic infection is therefore rare in COPD, but when it does occurP. aeruginosa has a range of colony forms (morphotypes) and adaptations including increasedmutability, reduced motility, reduced protease production and increased antibiotic resistance,similar to those seen in CF [44].

P. aeruginosa in non-CF bronchiectasis

P. aeruginosa is one of the most common isolates found in 12–43% of non-CF bronchiectasispatients (table 1). Stable patients with P. aeruginosa have poorer lung function and more sputum

production when compared with patients with other potentially pathogenic microorganisms(PPM) [45] and it has been associated with a poorer quality of life and more frequent hospitaladmissions [46]. There is debate over whether infection with P. aeruginosa leads to a faster declinein lung function as is seen in CF, or whether it is a marker of more damaged lungs [47, 48].

A recent study compared long-term colonisation with P. aeruginosa in 21 patients, of which six had CF, 10 had non-CF bronchiectasis and five had COPD. The authors typed 125 sequential

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isolates from sputa taken at least 1 month apart. The authors found a similar pattern of colonisation in all three diseases, with a dominant persistent clone, showing that the pattern of infection found in CF could also be shown in other conditions [49].

There have been no studies using genomic typing methods to investigate whether patients with non-CF bronchiectasis share strains of P. aeruginosa , but there has been one report of a patient with non-CF bronchiectasis acquiring LES from a relative with CF [50]. Interestingly, early studies using

pyocin typing and examining mucinophilic and chemotactic properties of P. aeruginosa suggest thatspecific subpopulations may have a predilection to infect bronchiectatic lungs [51, 52].

Pathogenicity of P. aeruginosa

P. aeruginosa possesses a range of virulence factors, although their expression may differ betweenisolates that cause acute infection and those responsible for chronic infection. Flagella, type IV pili,lipopolysaccharide and exopolysaccharides contribute to the adherence to cells and surfaces. TypeI and type II secretion systems export protein toxins, such as alkaline protease, elastase, exotoxin Aand phospholipase C, while type III secretion systems inject exoenzymes directly into eukaryoticcells. Other extra-cellular virulence factors include rhamnolipids, pyocyanin and hydrogen cyanide[53, 54]. Another pathogenicity factor is the ability to form alginate-enhanced biofilms [55], whichcontributes to the persistence of the organism rather than acute tissue damage and, together withother adaptations, promotes chronic infection (refer to later section).

Antibiotic resistance

P. aeruginosa is intrinsically resistant to many commonly used antibiotics and easily acquiresresistance by chromosomal mutation or the acquisition of new genes from other microorganismsby horizontal transfer [56]. In addition, the biofilm mode of growth also protects P. aeruginosa from antibiotics by a variety of mechanisms [57].

Little has been published specifically on antibiotic susceptibility of P. aeruginosa from patientswith non-CF bronchiectasis. In CF the prevalence of resistant P. aeruginosa is increasing as a resultof repeated antibiotic courses. Resistance rates are significantly higher than for strains originatingfrom patients without CF [58] and pan-resistant bacteria that are resistant to all antibiotics otherthan the polymixins have been described.

P. aeruginosa can develop resistance by either: 1) producing enzymes that destroy the antibiotic,such as AmpC b-lactamase, carbapenemases or aminoglycoside modifying enzymes; 2) modifyingthe antibiotic target, such as gyrA for quinolone resistance; or 3) reducing exposure either by adecrease in permeability or increased removal of the antibiotic from the bacterial cell (efflux).Efflux mechanisms often affect more that one class of antibiotics and therefore contribute tomulti-drug resistance [56].

Antibiotic resistance and its regulation can be complex in P. aeruginosa and various mechanismsthat affect resistance to a single antibiotic may be present in the same organism. For example, low level resistance to meropenem may be due to reduced permeability following changes to themembrane porin OprD. More resistance can result from an increase in an efflux pump that canremove the meropenem from the cell. Both mechanisms may be present and additive, leading tohigh-level resistance. Enzymes that can destroy meropenem (penemases such as VIM) do occurbut are currently rare [56].

AmpC codes for an inducible cephalosporinase which, when production is increased, can result inresistance to nearly all b-lactam antibiotics except the penems. Treatment with piperacillin orceftazidime can lead to the selection of bacteria that produce the enzyme constitutively rather than

just on induction. These are called derepressed mutants and offer a survival advantage. Imipeneminduces the AmpC b-lactamase, even though it is not affected by the enzyme, and it also inducesgenes involved with alginate production [59]. The regulation of ampC is exceedingly complex and

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is intimately linked to cell wall recycling [60–62]. Some mutations can reduce biologicalcompetitiveness and more work is needed to assess the link between antimicrobial resistance andfitness [61]. AmpR does not just regulate ampC but is a global transcriptional regulator thatregulates another b-lactamase PoxB, as well as proteases, quorum sensing and other virulencefactors [63]. Antibiotic resistance may therefore be associated with a change in virulence and/orfitness. This could explain why some CF patients respond to treatment for acute exacerbation,even though some of the P. aeruginosa are resistant to the antibiotic used [64].

P. aeruginosa possesses multi-drug efflux pumps that can expel a wide range of antibiotics and areresponsible for much of the organism’s intrinsic resistance to antimicrobials. For example,substrates for efflux pump MexAB-OprM include ticarcillin, aztreonam, piperacillin, ceftazidimeand tetracycline [65]. MexXY uses the same exit duct OprM and can export aminoglycosides,cefepime and ciprofloxacin. Antibiotic resistance may arise from an increase in the efflux pumpactivity, e.g. MexXY-OprM over-expression may be due to mutation in the regulatory gene mexZ and/or to mutations in the MexXY translocase genes [66].

Conversely, P. aeruginosa may be hyper-susceptible in vitro to some anti-pseudomonal antibioticsand susceptible to agents such as tetracycline and chloramphenicol to which P. aeruginosa would

normally be intrinsically resistant. This has been described in chronic infection in both CF andnon-CF bronchiectasis [67, 68], but the clinical relevance of these findings has not beeninvestigated. It was found that 25 out of 46 CF patients had strains hyper-susceptible to ticarcillindue to deficiencies in MexAB-OprM efflux activity, resulting from various gene defects includingreduced or abnormal expression of MexB and OprM [66]. It is unclear why this phenomenonexists. Efflux pumps do not just expel antibiotics and therefore reduced efflux may give a selectiveadvantage under certain physiological conditions in the chronically infected lung.

Adaptations to chronic infection

One of the characteristics of chronic infection with P. aeruginosa is the appearance in vitro of avariety of colony forms (morphotypes) that differ from those seen in environmental strains orthose causing acute infection (fig. 1).

Several different morphotypes may be found in the same sputum, even though the isolates areclonally related. These can include colonies lacking the typical pigmentation, mucoid forms, somethat look like coliforms, ‘‘dwarf’’ forms and very slow growing ‘‘small colony variants’’. One of themost easily recognised is the mucoid morphotype. This results from over-production of the

polysaccharide alginate, due to mutation in theregulatory genes. Hyper-alginate producers were ori-ginally thought unique to CF but they are also found in

non-CF bronchiectasis and COPD [45, 49, 69]. They are thought to be an adaptation to chronic infectionirrespective of the underlying cause. Alginate may protect against phagocytosis [70] and contribute to theformation of biofilms [71, 72]. Small colony variants(SCVs) have enhanced ability to form biofilms and may also contribute to persistence [73]. SCVs have only been described so far in CF but are easily missed unlesscultures are prolonged.

The phenotypic changes found in chronic infectionhave been studied extensively in CF but not in non-CFbronchiectasis. They include loss of acute virulencefactors, such as toxin production (e.g. elastase, phos-pholipase C, pyoverdin, hydrogen cyanide) and type IIIsecretion [74]. Many virulence factors are regulated by the quorum sensing (QS) system. These are signalling

Figure 1. Different pseudomonal morpho-

logical types of Pseudomonas aeruginosa

found in a single sputum sample taken from

a chronically infected individual.

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molecules that act on the regulators of gene transcription. Some QS molecules depend onpopulation density, and only have their effect when the number of organisms reaches a criticalconcentration (or quorum). P. aeruginosa QS molecules comprise acyl-homoserine lactones andmolecules of the PQS system. They can affect a large number of functions including pathogenicity,metabolic adaptation and persistence [75]. P. aeruginosa with mutations in QS genes, mostfrequently las R , do not respond to QS molecules and are surprisingly common, they were foundin 19 out of 30 CF patients in a study by S MITH et al . [76]. Las R mutants form characteristic

iridescent colonies and have also been cultured from patients with non-CF bronchiectasis (J.E.Foweraker, Papworth Hospital, Cambridge, UK; personal communication). These mutants do notproduce the toxins elastase, phenazines or hydrogen cyanide. Las R mutants can use a more diverserange of compounds as a source of carbon, nitrogen, phosphorus or sulphur and have a growthadvantage over the wild type when grown with phenylalanine, isoleucine or tyrosine. They therefore appear to be less pathogenic but better able to adapt to the local environment. Again,different phenotypes can co-exist so sputum may contain Las R mutants and organisms withoutthe mutation.

Longitudinal studies in CF have analysed strains from patients over several years. It is thought that

with time the bacteria adapt to a form that is less virulent but better able to persist in the damagedlung [76]. Multiple phenotypic variants of the underlying clonal population of P. aeruginosa co-exist and form a complex population in the chronically infected lung. This is described as‘‘adaptive radiation’’ and is thought to give the bacteria an advantage in that they can rapidly respond to changes in the environment, as individual organisms that have the necessary adaptation may already be present in the population.

Biofilms

P. aeruginosa is thought to grow in biofilms in chronic infections in both CF and non-CFbronchiectasis. Biofilm formation is thought to be a general adaptation to a hostile environmentand may allow persistence of infection by protecting the bacteria from the host response and theeffects of antibiotics. Biofilm fragments have been seen in CF sputum [77] and may contain amixture of P. aeruginosa plus other bacteria and even fungi, such as Candida spp . The extra-cellular matrix comprises alginate produced by P. aeruginosa plus proteins and DNA from othermicroorganisms and host cells. The biofilm contains a steep oxygen gradient and is anaerobic justbelow the surface. Different concentrations of nutrients and waste products will also be found indifferent areas of the biofilm. Therefore, the biofilm contains a wide range of physiologicalconditions, by which the bacteria possess a variety of adaptations that enable them to survivewithin these microniches [78].

Alginate protects P. aeruginosa in biofilms from interferon (IFN)-c activated macrophages [79].Neutrophils have been observed immobilised in the extra-cellular matrix, unable to penetrate thebiofilm [80]. It is thought that neutrophils may actually enhance early biofilm formation, asbiofilms formed in vitro in the presence of neutrophils are thicker and contain more bacteria [81].If P. aeruginosa and neutrophils are combined, the bacteria aggregate around necrotic dyingneutrophils. If neutrophil apoptosis is induced before the bacteria are added, the neutrophils areintact and the P. aeruginosa remain dispersed. Neutrophils can release DNA and F-actincomplexed with histones and other cations, and these may form the framework for the biofilm.The combination of DNAse and anionic polymers has a synergistic effect in clearing early neutrophil-associated biofilms in vitro and is being studied as a potential treatment to prevent or

disrupt early biofilm formation [81]. Neutrophil lysis is thought to be caused by rhamnolipid, atoxin produced by P. aeruginosa under QS control. Rhamnolipid may therefore help to protect thebiofilm from disruption by neutrophils, especially in the early stages of formation [82].

Azithromycin is a macrolide antibiotic that does not directly inhibit or kill P. aeruginosa, but it canblock QS and alginate polymer formation in vitro [83]. It can disrupt early biofilms formed by nonmucoid strains but has less effect on early biofilms formed by hyper-alginate producers

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(mucoid strains) or on established biofilms [84]. Azithromycin also has an anti-inflammatory effect in chronic lung infection and the relative importance of its diverse actions is yet to beestablished. Other antibiotics may also influence bacterial virulence. For example ciprofloxacin cansuppress alginate biosynthesis at concentration well below minimum inhibitory concentration(MIC) [85].

Bacteria cultured in biofilms in vitro are more resistant to most antibiotics than when they are

dispersed (planktonic). Several mechanisms have been proposed to explain this resistance [86]. Itwas thought that the extra-cellular matrix formed a physical barrier but there are channels withinthe biofilm through which most antibiotics can permeate. Positively charged antibiotics such ascolistin may bind to free anionic DNA and therefore not reach the bacteria, and an anionicantibiotic, such as an aminoglycoside (e.g. tobramycin) may bind to the alginate. If the AmpCb-lactamase is over produced by some P. aeruginosa it may form a high local concentration andprotect bacteria that can only produce basal levels of the enzyme. Mutability is increased inbiofilms, partly because of the presence of hypermutators but also because DNA can be damagedby the increased amounts of reactive oxygen species within the biofilm. The range of metabolicconditions in the biofilm may affect antibiotic susceptibility. P. aeruginosa can survive in the

anaerobic environment just below the surface of the biofilm by using nitrogen rather than oxygenas a terminal electron acceptor and aminoglycosides, such as tobramycin, cannot act on organismsthat are metabolising anaerobically. Organisms within a biofilm may become dormant andtherefore resist quinolones and b-lactam antibiotics [87]. These affects have been shown in an in vitro model of a young biofilm in a flow chamber using live/dead staining. Ciprofloxacin killsorganisms on the surface of the biofilm but cannot kill those deeply set within the biofilm, whereascolistin can kill the non-dividing cells in the centre [88]. The two antibiotics appear to be very effective against young biofilms in vitro and may explain why that combination is particularly effective in eliminating early infection with P. aeruginosa in CF.

HypermutatorsOne of the drivers of variability and adaptation seen in persistent infection in bronchiectasis isthought to be the presence of hypermutator (HM) bacteria [89]. These are P. aeruginosa with ahigher than usual spontaneous mutation rate and are thought to accelerate bacterial evolution.P. aeruginosa usually mutates at a frequency of one in 108–109, while mutation rates in HMbacteria can be as high as one in 100. HM P. aeruginosa were found in 37% of chronically infectedCF patients. This was the highest prevalence that had been described for a naturally occurringpopulation [90]. In comparison a HM prevalence of 1% in Escherichia coli and Salmonella spp . hadpreviously been considered high [91]. In a longitudinal study of CF patients in Denmark, none of the bacteria from early infections were found to be HMs but after 20 years of colonisation 65% of patients were infected with HM P. aeruginosa [92]. HM P. aeruginosa were described in 57% of chronically infected patients with COPD or non-CF bronchiectasis, suggesting that hyper-mutability is a general adaptation to long-term survival in the lung [93]. KENNA et al. [94] suggeststhat hypermutability is an extremely rare finding in environmental P. aeruginosa and in isolatesfrom newly infected CF patients.

Most of the information on HM P. aeruginosa comes from work on isolates from CF [95]. Hyper-mutability usually results from a primary mutation in genes of the MMR system, most commonly mutS and mutL , or defects in the GO system (mut M, Y and T ). The function of these systems is todetect and repair DNA replication errors and repair oxidative damage. MMR also inhibits

recombination between moderately diverged sequences and therefore reduces the acquisition of exogenous DNA through horizontal gene transfer [96].

HMs are uncommon in most bacterial populations because many of the mutations are deleterious.HM P. aeruginosa had reduced virulence and fitness both in vitro and in an animal model [97, 98].However, in changing environments or stressful conditions HM bacteria may be selected becausethey have adaptive mutations, such as antimicrobial resistance (referred to as ‘‘hitchhiking’’).

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The sequential acquisition of resistance to multiple antibiotics is seen in infection with P. aeruginosa in CF, and several studies in CF, non-CF bronchiectasis and COPD have shown that HM are morelikely to be antibiotic resistant than isolates with normal mutation rates [93, 99]. In a study of 29 CFpatients over a 5-year period, mutations accumulated at an average mutations rate of three per yearin HM P. aeruginosa compared with 0.25 per year in non-mutators. HM had more mutationsleading to antibiotic resistance but also more mutations in other genes such as lasR [89]. Therefore,other adaptations may provide a selective advantage for HM isolates, not just antibiotic resistance.

Two recent studies have shown that CF patients with HM had poorer lung function (FEV1

predicted), but longitudinal studies are needed to determine if this was due to infection with a HMor just an association, both being the result of prolonged infection [99, 100]. Work is needed onthe role of HM in non-CF bronchiectasis.

Chronic P. aeruginosa infection and the clinical microbiology laboratory

One practical implication of the range of phenotypic diversity of P. aeruginosa from non-CFbronchiectasis is that some isolates may be difficult to identify. Colonies of P. aeruginosa from

chronic infection may lack pigmentation, grow very slowly and may mimic other species.Commercial identification schemes that use biochemical reactions and assimilation tests are notreliable in identifying atypical P. aeruginosa and some of the other nonfermenting Gram-negativebacilli found in chronic infection, and therefore identification methods, such as species-specificPCR or sequencing of the 16S ribosomal RNA gene may be required [101].

Another consequence of phenotypic diversity is that a range of antimicrobial susceptibility patterns can be found in a population of P. aeruginosa in a single sputum sample (fig. 2). Bacteriawith the same morphotype may have different susceptibility and therefore resistant sub-populations may be missed, depending on which colony is picked for testing [68].

In CF, once a chronic infection is established the range in the antibiotic susceptibility of P. aeruginosa in a single sputum is so diverse that susceptibility testing methods are unreliable[102, 103]. It is currently unclear whether these findings can equally be applied to chronic infec-tion in non-CF bronchiectasis.

Finally it has been questioned whether current methods used for testing antimicrobialsusceptibility are relevant for bacteria that may be present in biofilms in the chronically infectedlungs. A variety of methods are being developed for testing biofilm susceptibility; however, theirclinical relevance still needs to be determined.

Streptococcus pneumoniae

S. pneumoniae is a Gram-positivecoccus appearing in pairs and inshort chains. It may be a harmlesscommensal in the oro-pharynx butcan cause severe and invasive dis-ease (pneumonia or meningitis).It can also cause otitis media orsinusitis, or lower airway infectionsin patients with damaged lungs suchas non-CF bronchiectasis or COPD,but it is rare in CF. AlthoughS. pneumoniae can be found in upto 37% of patients with non-CF

Figure 2. Variation in antimicrobial susceptibility testing. The figure

shows the results from testing two bacteria with identical colony

form in sputum taken from a patient with non-cystic fibrosis

bronchiectasis. The same six different antimicrobial discs were

used for both cultures. The susceptibility is proportional to the

diameter of the zone of diffusion around the antibiotic disc.

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bronchiectasis, very little has been published on its role in this condition. In COPD, S. pneumoniae has been cultured from both stable patients and those with exacerbation [20, 104]. The patient withnon-CF bronchiectasis due to an underlying antibody deficiency may be particularly susceptible torecurrent infections with S. pneumoniae [105]. Bronchiectasis in primary and secondary immunodeficiency patients is discussed further in the chapter by BROWN et al. [106].

S. pneumoniae has a polysaccharide capsule that helps evade opsonisation, and isolates lacking the

capsule are avirulent. There are over 90 capsule types and the capsule type may be one of several factorsthat determine the pathogenicity of an individual strain [107]. A polyvalent vaccine containing themost common serotypes is available and recommended for use in patients with chronic lung disease.

S. pneumoniae can use a wide variety of molecules to adhere to host cells and produces an IgAprotease and a toxin, pneumolysin that can promote invasion, inflammation and tissue damage[108]. Pneumolysin is proinflammatory and has many actions including cytolysis, inhibition of cilial beating, and direct activation of the classical complement cascade. Although it is not acommon pathogen in CF, isolates of S. pneumoniae from CF sputum have characteristics that may be associated with adaptation to persistence in the lung, i.e. hypermutability and the ability toform biofilms [109, 110]. Further work is needed to clarify the role of the different virulence

factors in order to understand why S. pneumoniae may be a harmless commensal or cause non-invasive respiratory tract infection (in COPD or bronchiectasis) or produce severe invasive diseasewith bacteraemia.

The prevalence of antibiotic resistant S. pneumoniae has increased and in some countries very highrates of resistance to penicillin, macrolides and tetracyclines limit the treatment options. Penicillinresistance is due to modifications to penicillin binding proteins not by the production of ab-lactamase and, therefore, amoxicillin–clavulanate is ineffective.

Moraxella catarrhalis

M. catarrhalis is a Gram-negative diplococcus that was previously named Branhamella or Neisseria catarrhalis . Like NTHi it is a common commensal organism in the upper respiratory tract and cancause otitis media or sinusitis. It was not reported in studies of non-CF bronchiectasis in the 1960sas it was considered an oral contaminant rather than a PPM. However, it can be cultured insignificant numbers from sputum or PSB in up to 27% of patients with non-CF bronchiectasis [7].It is also considered a significant pathogen in COPD but is only rarely isolated in CF.

A longitudinal study of M. catarrhalis in 29 patients with non-CF bronchiectasis found that patientswere colonised with a variety of strains with average colonisation duration of 2.3 months for eachstrain. No association between strain acquisition and exacerbation was found and as M. catarrhalis was often in mixed culture with other PPMs (H. influenzae or S. pneumoniae ), it was difficult todetermine whether it had an independent pathogenic role [111]. In a study of 50 patients withCOPD, the average time from acquisition to clearance of a new strain of M. catarrhalis was 1 monthand re-infection with the same strain was rare, suggesting that there was an effective immuneresponse. Of the new acquisitions, 47% were associated with an exacerbation [112]. Acquisition of M. catarrhalis led to an increase in airway inflammation, characterised by a rise in sputum neutrophilelastase, interleukin (IL)-8, tumour necrosis factor (TNF)-a and a reduction in secretory leukocyteprotease inhibitor (SLPI) [113].

Putative virulence factors of M. catarrhalis include several outer membrane proteins plus LOS and

these affect cell adhesion, epithelial cell invasion, serum resistance and biofilm formation [114].More work is needed to understand the pathogenesis of infection in both COPD and non-CFbronchiectasis.

More than 90% of M. catarrhalis produce a b-lactamase (BRO-1 or BRO-2) and are resistant toampicillin. Acquired resistance to other antibiotics is rare with most remaining susceptible tomacrolides, tetracyclines, amoxicillin-clavulanic acid and quinolones [115].

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Staphylococcus aureus

S. aureus is a Gram-positive coccus found in clusters that may be part of the normal flora in theanterior nares, throat and on moist skin sites such as groin and axilla. Infection is characterisedby abscess formation, particularly in skin and soft tissues. It is a rare cause of respiratory tractinfection, but can cause severe pneumonia after influenza. It is a common cause of early infection in CF but is less common in non-CF bronchiectasis where its presence may indicateundiagnosed CF [10]. There is also an association of S. aureus with ABPA in non-CFbronchiectasis [116].

S. aureus produces a range of exotoxins that can cause tissue damage. It is also thought to formbiofilms on prosthetic devices and thereby evade the host response and resist antimicrobialtherapy [117]. Biofilm-like aggregates of S. aureus surrounded with the polysaccharide poly-N -acetyl-glucosamine have been observed in anaerobic conditions in CF mucus and can resistnonoxidative killing [118]. Persistence of S. aureus in CF and prosthetic infections has also beenrelated to the presence of small colony variants. These tiny colonies are difficult to identify in vitro .They are associated with treatment with trimethoprim/sulphamethoxazole or aminoglycosides,

are more antibiotic resistant than the typical forms in the same sputum and may survive withinhost cells [119].

The ability of S. aureus to rapidly adapt and persist in the lung may be a result of genomicinstability due to mobilisation of bacteriophages. Isolates from the anterior nares of CF patientshad a higher frequency of genomic alterations than those from healthy controls [120]. A higherproportion of hypermutable strains of S. aureus were found in CF patients when compared withisolates from bacteraemia or other respiratory infections. As with other species with high mutationrates, many of these had defects in mutS [121].

Meticillin resistant S. aureus (MRSA) are resistant to all penicillins, cephalosporins and penemsand are often also resistant to other classes of antibiotics (macrolides, fluoroquinolones andaminoglycosides). They can be difficult to treat, partly because oral options are limited butalso because the active parenteral options (glycopeptides) may be less effective comparedwith the use of a b-lactam antibiotic to treat a susceptible isolate. It may be difficult to clearMRSA carriage from patients with bronchiectasis, but there is data from CF that showsthat a combination of systemic treatment with skin antisepsis and inhaled antibiotics may beeffective [122].

Burkholderia spp. and other non-fermenters

Burkholderia spp are plant pathogens and are a major cause of morbidity and mortality in CF butare rarely encountered in other conditions. In spite of the frequent presence of these bacteria in theenvironment, and their propensity for spread between CF patients, there are only two case reportsof infection in non-CF bronchiectasis, one with Burkholderia cepacia complex (not speciated) andanother with Burkholderia gladioli [123, 124].

A wide variety of other nonfermentative Gram-negative bacilli can occasionally act as opportunisticpathogens in the human lung. Species of the genera Achromobacter , Stenotrophomonas, Ralstonia,Pandoraea and Inquilinus can cause infection in the CF lung, and S. maltophilia and Achromobacter (previously Alkaligenes ) xylosoxidans have been reported in non-CF bronchiectasis (table 1). Many are both intrinsically resistant to some antibiotics and easily acquire resistance. They can be difficultto identify in the laboratory and molecular methods are recommended to ensure accurateidentification [101]. In particular it is important to differentiate these organisms from theBurkholderia spp . because of the need to prevent cross infection. There is too little experience withthese microorganisms to comment on their propensity for colonisation, infection, or role inexacerbation of non-CF bronchiectasis.

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Anaerobes and other bacteria considered normal upperrespiratory tract flora

Sputum may contain microorganisms other than the PPM. These have been considered eithercontaminants from the upper respiratory tract or harmless commensals colonising the sputum.This assumption has been challenged following studies using both conventional culture methods

and culture-independent techniques.Sputum is not routinely cultured for anaerobes partly because they are present in large numbers insaliva and can easily contaminate expectorated sputum, but also because some are very difficult toculture. Following the observation of a rapid drop in oxygen partial pressure just below the surfaceof a CF sputum plug, investigators began to look for anaerobes in the sputum from CF and non-CF bronchiectasis [125]. Obligate anaerobes in particular Prevotella spp . were found in significantnumbers, far more than would be expected from oral contamination [126–128]. Their significancein disease has been questioned as high numbers of bacteria were found in a stable CF patient inone study, and the numbers of anaerobes remained constant during successful treatment of aclinical exacerbation [129].

It has been proposed that members of the Streptococcus milleri group may have a role in chroniclung infection. One study followed the changes in the microbial flora during and betweenpulmonary exacerbations of CF using both culture and culture-independent methods. The groupidentified members of the S. milleri group as of potential importance in exacerbations both in CFand in two patients with non-CF bronchiectasis [130].

Following an observation that a range of upper respiratory tract flora were seen in large numbersin sputum from CF patients, a Staphylococcus sp. (not S. aureus ) and a viridans-type Streptococcus sp. were further studied. While not intrinsically pathogenic, they were able to enhance thevirulence of P. aeruginosa in an animal model and increase the expression of certain virulence

genes of P. aeruginosa in vitro . This could be reproduced using an inter-species QS molecule, AutoInducer-2 (AI-2) [131]. Of interest, the oral anaerobe Prevotella also produces AI-2 [127]. Thecomplex pattern of interaction between microorganisms in ecosystems other than the lung hasbeen described and it is known that microorganisms can enhance or inhibit growth of other co-habitants [132]. The studies in CF show that interactions may also enhance pathogenicity [133].

The CF lung, therefore, may contain a mixture of microorganisms that includes those that aredirectly pathogenic, those that behave as commensals and those that are not directly pathogenicbut may increase the virulence of other organisms. Although this has not been studied in non-CFbronchiectasis, microorganisms other than PPMs are regularly observed in sputum cultures incombination with PPMs and further work on these potential interactions is needed.

Culture-independent studies of microbial flora in the lung

There have been attempts to describe the composition and diversity of the microbes in the lungirrespective of the ability to culture individual microorganisms. One approach is to analyse thegene encoding 16S rRNA. This is present in all true bacteria and the sequence variation is sufficientto identify most genera and many species. Genetic material can be extracted from a clinical sample,and the 16S rRNA gene amplified by PCR. The product may be analysed looking at terminalrestriction fragment length polymorphisms (TRFLP). This compares the size of the terminal

fragment of rRNA after cutting with a restriction enzyme; the length of the fragment beingcharacteristic of certain species. Alternately the PCR product can be cloned, sequenced andcompared with databases containing sequence data from a wide range of microorganisms. Thesemethods and other variations have been applied to patients with CF and non-CF bronchiectasis todescribe the diversity of microorganisms, and have revealed species not previously found inrespiratory samples using traditional culture methods [12, 134–136]. While the presence of nucleicacid does not necessarily indicate the presence of viable organisms, a comparison of RT-TRFLP

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with TRFLP showed that a high proportion of the bacterial species detected in CF sputum weremetabolically active [137].

There have been major technical advances facilitated by the development of next generationsequencers plus developments in bioinformatics. These have allowed direct analysis of amplifiedDNA without the cloning step, and greater depth of sequencing of 16S rRNA DNA [138, 139]. Analternative approach is to attempt whole genome sequencing directly from the clinical sample [140].

This could include analysis of nucleic acid from eukaryotes and viruses in sputum as well as bacteria[141]. Such techniques can provide an enormous amount of information that is a great challenge toprocess. However, they offer the potential for a far more sophisticated analysis of the geneticvariability found in single species and the variety of microorganisms in chronic lung infection.

Respiratory viruses

The role of viruses in non-CF bronchiectasis is not known and remains an important area forfuture research. Some data exists that viral infections in childhood may predispose to thedevelopment of bronchiectasis in later life [142], whether it is through the development of

bronchiolitis, disruption of small airway associated innate/adaptive immunity, damage of airway epithelia or compromise of mucociliary clearance, it is unclear.

What is also unclear is the role that viral infection plays in triggering infective exacerbations andprogressive lung damage in patients with non-CF bronchiectasis where no studies have to datebeen carried out. Therefore, only cautiously can parallels be drawn from studies examining therole of viruses in asthma, COPD and CF.

Viral infections in asthma, COPD and CF

Viral exacerbation of asthma has been well published. In a study by JOHNSTON et al [143] usingPCR and viral culture, viruses were detected in 80% of episodes of wheeze or reduced peak expiratory flow in children aged 9–11 years with asthma. Rhinovirus accounted for 61% of theviruses detected, coronavirus 16%, influenza 9%, parainfluenza 9% and respiratory syncytial virus(RSV) 5%. Similarly, NICHOLSON et al . [144] found that respiratory viruses accounted for 44% of asthma exacerbations in adults. Respiratory viruses were also present in most patients hospitalisedfor life-threatening asthma and acute not life-threatening asthma [145].

The application of molecular diagnostic methods has improved the understanding of viralepidemiology. Respiratory viruses may induce asthma exacerbations via direct effects on theairway epithelium as well as through a systemic immune reaction.

Rhinovirus is the most common respiratory virus and represents two-thirds of all upper respiratory tract infections. It also accounts for 50% of asthma exacerbations in children [146]. Traditionally,rhinovirus is thought to infect the upper respiratory epithelium. However, rhinovirus is also capableof replicating in the lower airway cells during experimental infection [147]. PAPADOPOULOS et al . [148]showed that both rhinovirus genomic material and replicative strand RNA were detectable inbronchial biopsies using in situ hybridisation in 50% of adult volunteers subjected to an experimentalrhinovirus upper respiratory infection.

The mechanism by which viruses cause bronchoconstriction is not fully understood, but it is likely to involve cytokine production in response to viral replication in the lower airways, which includesupregulating the expression of a range of proinflammatory mediators. The proinflammatory cytokine IL-1b is detectable in experimental infected individuals. IL-8, a key mediator inneutrophil-mediated acute inflammation, is also detected in naturally occurring infectionscorrelating with neutrophilia in blood and nasal samples in children with virally precipated asthmaor experimental infection [149]. Other mediators induced by rhinovirus infections includeneutrophil-activating peptide (which induces neutrophil migration), eotaxin and RANTES

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(regulated on activation, T-cell expressed and secreted), IL-16 and monocyte chemoattractantprotein (MCP-1). All of these can lead to enhance airway inflammation.

RSV was detected in only 5% of asthma episodes in the study by JOHNSTON [143]. However, it isknown to be a potent cause of wheezing, particularly in infancy. It has been shown that G-glycoprotein of RSV appears to stimulate T-helper cell (Th) type 2 immune response in the upperairway, whether or not if the infant is atopic [150]. Th2 cytokine patterns are known to be associated

with viral immunopathology and allergic-type responses, in contrast to Th1 cytokine patterns, whichare classically associated with viral elimination. Interestingly, the nasal cytokine responses to otherviruses are of the predominant Th1 type (except RSV). This could explain the tendency for RSV tocause wheezing, but not the association between other respiratory viruses and wheezing.

Influenza A infection induces large amounts of intrapulmonary IFN-c and enhances both laterallergen specific asthma and dual Th1/Th2 responses [151]. TERAN et al . [152] also demonstartedthat the eosinophil product, major basic protein (MBP), and RANTES increased with viralinfections, and there was a correlation in the concentration of RANTES with clinical symptoms. Inaddition, epithelial cells infected with influenza in vitro were associated with an increase in eotaxin[153]. Eotaxin can in turn lead to an exaggerated inflammatory response by being an agonist for

chemokine receptor 3, which can be found on eosinophils, T-cells and basophils. These are all key factors in asthma exacerbation.

Patients with asthma are no more susceptible to upper respiratory tract rhinovirus infections thanhealthy people, but suffer from more severe consequences of the lower respiratory tract infection.Recent epidemiological studies suggest that viruses provoke asthma attacks by additive orsynergistic interactions with allergen exposure or with air pollution. An impaired antiviralimmunity to a rhinovirus may lead to impaired viral clearance and hence prolonged symptoms.Indirect prevention strategies focus on the reduction of overall airway inflammation to reduce theseverity of the host response to respiratory viral infections. There is a lack of specific antiviral

strategies in the prevention or reduction of viral-triggered asthma exacerbations. Recent advancesin the understanding of the epidemiology and immunopathogenesis of respiratory viral infectionsin asthma may provide opportunities or the identification of specific targets for antiviral agentsand strategies for management and prevention.

COPD is the fourth leading cause of mortality worldwide and is an important cause of globalburden of disease [154]. The disease is associated with intermittent exacerbations characterised by acute deterioration in symptoms, lung function, and quality of life [155, 156]. Exacerbations havemajor effects on health status and are associated with considerable morbidity and mortality thatcan lead to hospital admission with high treatment costs [157].

Infectious agents are recognised as a major pathogenic factor in exacerbations. Bacteria have a role inthe pathogenesis [158, 159] and the exacerbations of COPD. However, bacteria are absent in about50% of exacerbations and the frequency of isolation does not increase during exacerbation [160].

Early studies looking at respiratory viruses and COPD have stated a 20% detection rate in COPDexacerbations [161, 162]. However, these studies were limited by using less sensitive methods inviral detection. SEEMUNGAL et al . [163] detected respiratory viruses from nasal samples and bloodof patients with COPD using a combination of culture, serology and PCR. They showed that 64%of COPD exacerbations were associated with a cold occurring up to 18 days before exacerbation.In total, there were 168 episodes of COPD exacerbation in 53 patients and 77 viruses (39 wererhinoviruses) were detected. Viral exacerbations were associated with frequent exacerbatons,increased symptoms, a longer median symptom recovery period (up to 13 days) and a tendency towards higher plasma fibrinogen and serum IL-6 levels. RSV has also been shown to be animportant virus in COPD exacerbations and was detectable in 11.4% of patients admitted intohospital [164]. Patients with stable COPD may carry respiratory viruses. Non-RSV respiratory viruses were detected in 11 (16%), and RSV in 16 (23.5%) out of 68 stable COPD patients, withRSV detection being associated with higher inflammatory marker levels [161, 164].

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Early studies looking at respiratory viruses in CF relied on repeated serological testing, either alone[165], or in combination with viral cultures for viral detection [166–170]. These methods arerelatively insensitive and more recent studies have utilised molecular based methodologies [171–175].All these studies produced different results in terms of prevalence of respiratory viruses in CF, thesedifferences could be due to the different methodologies utilised. It is also likely that there aredifferences in the populations studied, as the prognosis for CF has improved with each successivebirth cohort.

It has now been 25 years since WANG et al . [169] described the relationship between respiratory viral infections and the deterioration in clinical status in CF patients. Viruses were identifiedthrough repeated serology and nasal lavages for viral isolation in 49 patients with CF (mean age13.7 years) over a 2-year period. Although the CF patients had more respiratory illnesses than thesibling controls (3.7 per year versus 1.7 per year), there were no differences in virus identificationrates (1.7 per year). The rate of proven virus infection was significantly correlated with the declinein forced vital capacity (FVC) and FEV1, Shwachman score, and frequency and duration of hospitalisation.

More recent studies suggest no difference in the frequency of either upper respiratory tract illness

episodes [166] or proven respiratory viral infections [168] between children with CF and healthy controls; however, children with CF have significantly more episodes of lower airway symptomsthan controls [166, 168]. R AMSEY et al . [168] prospectively compared the incidence and effect of viral infections on pulmonary function and clinical scores in 15 school children with CF aged5–21 years and their unaffected siblings. Over a 2-year period, samples were taken at regular2-month intervals and during acute respiratory illnesses for pharyngeal culture and serology forrespiratory viruses. There were a total of 68 acute respiratory illness (ARI) episodes that occurredin the patients with CF, in 19 of these episodes an associated virus identified. A total of 49 infectiveagents were identified either during ARIs or at routine testing in the patients with CF; 14 wereidentified on viral isolation (rhinovirus on 11 occasions), whilst 35 were isolated on

seroconversion (parainfluenza virus on 12, RSV on nine and Mycoplasma pneumoniae on six occasions). There was no significant difference in the rate of viral infections between the patientswith CF and their sibling controls, as measured either by culture or serology. The rate of viralinfections was higher in younger children (both CF and controls), and the rate of decline inpulmonary function was greater in the younger children with CF with more viral infections. At thetime of an ARI, the virus isolation and seroconversion (four-fold increase in titres) rates were 8.8%and 19.1%, respectively, in children with CF compared with 15% and 15%, respectively, for thesiblings not affected. In contrast the rates for virus isolation and seroconversion at routine2 monthly visits were 5.6% and 16.2%, respectively, for children with CF and 7.7% and 20.2%,respectively, for the siblings not affected.

Similarly HIATT et al. [166] assessed respiratory viral infections over three winters in 22 infantsless than 2 years of age with CF (30 patient seasons) and 27 age matched controls (28 patientseasons). The average number of acute respiratory illness per winter was the same in the controland the CF groups (5.0 versus 5.0). However, only four of the 28 control infants had lowerrespiratory tract symptoms in association with the respiratory tract illness, compared with 13 outof the 30 infants with CF (OR -4.6, 95% CI 1.3–16.5; p-value ,0.05). Seven of the infants withCF cultured RSV, of whom three required hospitalisation. In contrast, none of the controlsrequired hospitalisation. Pulmonary function measured by rapid chest compression techniquewas significantly reduced in the infants with CF after the winter months and was associated withtwo interactions; RSV infection with lower respiratory tract infection and male sex with lower

respiratory tract infection.

From previous reports, two viral agents appear to have the greatest effect on respiratory status inCF, namely RSV and influenza, possibly because the uses of viral culture and serology haveunderestimated the effects of rhinovirus (due to the vast amount of serotypes). In youngerchildren, RSV is a major pathogen resulting in an increased rate of subsequent hospitalisation.ABMAN et al . [176] prospectively followed up 48 children with CF diagnosed through newborn

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screening and documented the effect of RSV infection. 18 of the infants were admitted intohospital a total of 30 times over a mean follow-up period of 28 months (range 5–59 years). Inseven of these infants RSV was isolated, and their clinical course was severe with three requiringmechanical ventilation and five necessitating chronic oxygen therapy. Over the next 2 years theseinfants had significantly more frequent respiratory symptoms and lower chest radiograph scoresthan non-RSV identified infants. In another prospective study of repeated BAL in 80 infantsidentified through CF newborn screening over a 5-year period, 31 infants were hospitalised for a

respiratory exacerbation, 16 (52%) of which had a respiratory virus identified with the mostcommon being RSV (n57).

In older children and adults with CF, influenza seems to have the greatest effect. P RIBBLE et al .[167] assessed acute pulmonary exacerbation isolates from 54 patients with CF. Over the year of the study 80 exacerbations were identified, of which 21 episodes were associated with an identifiedviral agent (influenza A: five episodes; influenza B: four episodes; RSV: three episodes) with mostagents identified by serology. Compared with other agents, infection with influenza was associatedwith a more significant drop in pulmonary function (FEV1 decreased by 26% compared with 6%,respectively). A retrospective study in older patients with chronic P. aeruginosa infection reported

an acute deterioration in clinical status in association with influenza A virusl infection [177].COLLINSON et al . [171] followed 48 children with CF over a 15-month period using a combinationof viral culture and PCR for picornaviruses alone [178]. 38 children completed the study and therewere 147 symptomatic upper respiratory tract infections (2.7 episodes per child per year), withsamples available for 119 episodes. Picornaviruses were identified in 51 (43%) of these episodes, of which 21 (18%) were rhinoviruses. In those children old enough to perform spirometry there weresignificant drops in both FVC and FEV1 in association with upper respiratory tract infection, withlittle difference in the severity of drop whether a picornavirus was identified or not. Maximal meandrop in FEV1 was 16.5%, at 1–4 days after onset of symptoms, but a deficit of 10.3% persisted at21–24 days. Those with more upper respiratory tract infections appeared to have a greater change

in total Shwachman and Crispin–Norman scores over the study. Six children isolated aP. aeruginosa for the first time during the study, five at the time of a upper respiratory tractinfection and only one was asymptomatic at the time of first isolation. The data from this study has to be handled with care as the term ‘‘upper respiratory tract illness (URTI)’’ did not necessarily imply a positive viral isolation.

PUNCH et al . [173] used a multiplex RT-PCR assay combined with an enzyme-linked ampliconhybridisation assay (ELAHA) for the identification of seven common respiratory viruses in thesputum of 38 CF patients. 53 sputum samples were collected over two seasons and 12 (23%)samples from 12 patients were positive for a respiratory virus (influenza B n54, parainfluenza 1n53, influenza A n53, RSV n52). There were no statistical associations between virus status anddemographics, clinical variables or isolation rates for P. aeruginosa , S. aureus or Aspergillus

fumigatus .

OLESEN et al. [174] obtained sputum/laryngeal aspirated from children with CF over a 12-monthperiod in outpatient clinics. They achieved a viral detection rate of 16%, with rhinovirus being themost prevalent virus. However, this virus did not seem to have any devastating impact on lungfunction. However, the other viruses detected were associated with significant reduction in lungfunction. The authors failed to show a positive correlation between respiratory viruses andbacterial infections in their studied population, as the type or frequency of bacterial infectionduring or after viral infections were not altered. They also demonstrated that clinical viral

symptoms had a very poor predictive value (0.39) for a positive viral test.

WAT et al . [179] utilised ‘‘real-time’’ nucleic acid sequence-based amplification (NASBA) toexamine the role of respiratory viruses in CF. They achieved a rate of 46% for respiratory viruses intheir paediatric CF cohort during reported episodes of respiratory illness. The results comparefavourably with previous studies, this may be due to earlier studies relying heavily on repeatedserological testing either alone [165] or in combination with viral isolation [166–170]. These traditional

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methods are relatively insensitive and once again may have underestimated the prevalence of viruses in CF.

Detection of respiratory viruses

The principal laboratory methods utilised for the diagnosis of respiratory viruses, rely upon thedetection of the virus in respiratory secretions and therefore an important factor in respiratory

viral diagnosis is the necessity for the submission of an appropriate sample for testing. Inadequateor improper specimen collection and transport account for the largest source of error in theaccuracy of viral detection results [180]. Nasal swabs, nasopharyngeal aspirates, nasal wash andsputum specimens are generally considered as the specimens of choice for the detection of respiratory viruses [173, 180–183]. A prospective study by HEIKKINEN et al . [184] showed that thesensitivity of nasal swabs was comparable to nasopharyngeal aspirates for the detection of all majorrespiratory viruses by tissue culture, with the exception of RSV.

Molecular techniques have superseded many ‘‘conventional’’ methods utilised for respiratory viraldetection, such as viral culture and serology analysis, due to the rapid turn-around time for the

results. Molecular assays have particular advantages where the starting material available isacellular (swab) or where surveillance samples have a low copy number of the viral target. Therapid turn-around time of results allows diagnostic virology to have an impact on patientmanagement, thereby avoiding prescribing the inappropriate use of antibiotics and allowing thecorrect prescription for anti-virals. It may also play an important role in infection control in thehospital setting.

Interaction between bacteria and viruses

There is very little known about the interaction between respiratory viruses and bacteria in non-CF

bronchiectasis but a number of publications suggest that respiratory viruses may precipitatesecondary bacterial infection in CF. In a 25-year retrospective review from the Danish CF clinic,the most likely first isolation of P. aeruginosa was found to be occur between October and March[185], coinciding with the peak of the RSV season. This observation implies a causal relationshipbetween respiratory viral and bacterial infection.

The first bacterial isolation of a given organism in CF has also been shown to often follow a viralinfection. In the 17-month prospective study reported by COLLINSON et al . [171], five of the six firstisolations of P. aeruginosa were made during the symptomatic phase of an upper respiratory tractinfection or 3 weeks thereafter. In contrast only one of the six initial infections with P. aeruginosa was identified during the asymptomatic period. Similarly, H. influenzae was recovered for the firsttime from three children within 3 weeks of an upper respiratory tract infection and the one new S. aureus infection was identified immediately following a viral infection.

ARMSTRONG et al. [170] have reported that 50% of CF respiratory exacerbations requiringhospitalisation are associated with the isolation of a respiratory virus. In their prospective study of repeated BAL in infants over a 5-year period, a respiratory virus was identified in 52% of theinfants hospitalised for a respiratory exacerbation, most commonly RSV. 11 of the 31 hospitalisedinfants (35%) acquired P. aeruginosa in the subsequent 12–60-month follow-up period, comparedwith three out of 49 (6%) non-hospitalised infants (relative risk 5.8).

Respiratory viruses can disrupt the airway epithelium and precipitate bacterial adherence. Forexample influenza A infection results in epithelial shedding to basement membrane with submucosaloedema and neutrophil infiltrate [186], while both influenza and adenovirus have a cytopathic effecton cultured nasal epithelium leading to the destruction of the cell monolayer [187]. This epithelialdamage results in an increase in the permeability of the mucosal layer [188, 189], possibly facilitatingthe bacterial adherence. Bacteria can also utilise viral glycoproteins and other virus-induced receptorson host cell membranes as bacterial receptors, in order to adhere to virus infected cells [190, 191].

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The lower respiratory tract is protected by local mucociliary mechanisms that involve theintegration of the ciliated epithelium, periciliary fluid and mucus. Mucus acts as a physical andchemical barrier onto which particles and organisms adhere. Cilia lining the respiratory tractpropel the overlying mucus to the oropharynx where it is either swallowed or expectorated.Influenza viral infection has been shown to lead to the loss of cilial beat, and shedding of thecolumnar epithelial cells generally within 48 hours of infection [192]. P ITTET et al . [193] showedthat a prior influenza infection of tracheal cells in vivo does not increase the initial number of

pneumococci found during the first hour of infection, but it does significantly reduce mucociliary velocity, and thereby reduces pneumococcal clearance during the first 2 hours after pneumococcalinfection at both 3 and 6 days after an influenza infection. The defects in pneumococcal clearancewere greatest 6 days after an influenza infection. Changes to the tracheal epithelium induced by influenza virus may increase susceptibility to a secondary S. pneumoniae infection by increasingpneumococcal adherence to the tracheal epithelium and/or decreasing the clearance of S. pneumoniae via the mucociliary escalator of the trachea, and thus increasing the risk of secondary bacterial infection.

DE VRANKRIJKER et al . [194] showed that mice that were co-infected with RSV and P. aeruginosa hada 2,000 times higher CFU count of P. aeruginosa in the lung homogenates compared with micethat were infected with P. aeruginosa alone. Co-infected mice also had more severe lung functionchanges. These results suggest that RSV can facilitate the initiation of acute P. aeruginosa infection.

RSV has also been shown to increase adherence of NTHi and S. pneumoniae to human respiratory epithelial cells in vitro [195]. This increase adherence could be explained by an upregulation of cellsurface receptors for bacteria, such as intercellular adhesion molecule-1 (ICAM-1), carcinoem-bryonic adhesion molecule 1 (CEACAM1) and platelet activating factor receptor (PAFr). Anotherstudy also showed that NTHi and S. pneumoniae bind to both free RSV virions and epithelial cellstransfected with cell membrane-bound G protein, but not to secreted G protein. Pre-incubation withspecific anti-G antibody significantly reduce bacterial adhesion to G protein-transfected cells [196].

STARK et al . [197] showed that mice that were exposed to RSV had significantly decreasedS. pneumoniae , S. aureus or P. aeruginosa clearance between 1 to 7 days after RSV exposure. Micethat were exposed to both RSV and bacteria had a higher production of neutrophils inducedperoxide, but less production of myeloperoxidase compared with mice that were exposed toS. pneumoniae alone. This suggests that functional changes in the recruited neutrophils may contribute to the decreased bacterial clearance.

More recently, CHATTORAJ et al . [198] demonstrated that acute infection of primary CF airway epithelial cells with rhinovirus liberates planktonic bacteria from biofilm. Planktonic bacteria,which are more proinflammatory than their biofilm counterparts, stimulate increased chemokine

responses in CF airway epithelial cells which, in turn, may contribute to the pathogenesis of CFexacerbations.

Collectively, these findings suggest that respiratory viruses may lead to epithelial disruption,destruction of mucociliary escalator, increased cytokine production, neutrophil influx andincreased neutrophil induced peroxide release, indirectly facilitating bacterial infection of theairway. Whether these are the mechanisms for infective exacerbations in the context of non-CFbronchiectasis remains to be seen.

Prevention and treatment of infection with respiratory viruses

Influenza associated death is between 13,000 to 20,000 incidents per year throughout the wintermonths in the UK [199], though some of the deaths may be attributed to RSV. Influenza vaccines arethe only commercially available vaccines against respiratory viruses. Recent vaccines containantigens of two influenza A subtypes, strains of the currently circulating H3N2 and H1N1 (Swineflu) subtypes, and one influenza B virus. The waning of vaccine-induced immunity over timerequires annual re-immunisation even if the vaccine antigens are unchanged. Influenza vaccination

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is recommended to those with chronic respiratory diseases including non-CF bronchiectasis. Despitethis recommendation, there is neither evidence for, nor against, routine annual influenza vaccinationfor children and adults with non-CF bronchiectasis from a recent Cochrane review [200].

Although there is no licensed RSV vaccine to date, prophylaxis using a humanised mousemonoclonal antibody, Palizivumab, which has been shown to reduce the rate of RSV associatedhospitalisation in premature infants [201].

Amantadine has been the conventional anti-viral against of influenza. Its mode of action involvesinterfering with viral protein M2, thereby inhibiting the replication of influenza viruses by interfering with the uncoating of the virus inside the cell. However, it is strain specific as it is only effective against influenza A and has common side-effects such as insomnia, poor concentrationand irritability. Amantadine has now been almost completely replaced by neuraminidaseinhibitors (NI), except for some NI-resistant influenza.

Neuraminidase inhibitors

NIs such as Zanamivir and Oseltamivir are licensed for the treatment of influenza A and B, avian flu

(H5N1) and Swine flu (H1N1). They work by inhibiting the function of the viral neuraminidaseprotein, thus preventing the release of the progeny influenza virus from infected host cells, a processthat prevents infection of new host cells and thereby halts the spread of the infection in therespiratory. Early initiation of these therapies within 48 hours from the onset of symptoms canreduce the duration of common cold symptoms by 1–2 days [202, 203]. Zanamivir has a poor oralbioavailability and intranasal application has been shown to be effective in treating experimentalinfluenza infection, by the reduction in symptoms caused, virus shedding and the development of otitis media [204]. A phase III study is currently underway that looks at the efficacy of intravenousZanamivir preparation. However, compassionate use of i.v. Zanamivir could be considered to treatcritically ill adults and children having a life-threatening condition, due to suspected or confirmed

pandemic Influenza A (H1N1) infection or infection due to seasonal Influenza A or B virus, who arenot responding to oral or inhaled neuraminidase inhibitors. A recent systematic review meta-analysis showed that neuraminidase inhibitors only have modest effectiveness (Oseltamivir andZanamivir 61 and 62%, respectively) against flu-like symptoms in previously healthy subjects [205].

Ribavarin

Ribavarin, a synthetic guanosine nucleoside that has a broad spectrum of antiviral activity, isapproved treatment for lower respiratory tract disease caused by RSV [206]. It can be incorporatedinto RNA as a base analog of either adenine or guanine, it pairs equally well with either uracil or

cytosine, inducing mutations in RNA-dependent replication in RNA viruses. Controlled studiesalso show that the use of ribavarin is effective in reducing the clinical severity score, duration of mechanical ventilation, supplemental oxygen use and days of hospitalisation [207].

Macrolides

Although rhinovirus is the major cause of colds, its vast amount of serotypes has madedevelopment of anti-virals against it problematic. 90% of rhinovirus serotypes gain entry intoepithelial cells using ICAM-1 cellular receptors and blockade of these receptors in experimentalstudies have shown reduced infection severity [208]. Macrolide antibiotics, bifilomycin A1 and

erythromycin, have been shown to inhibit ICAM-1 epithelial expression and hypothesis abouttheir potential as anti-virals have yet to be proven, more clinical proof is required [209].

Other anti-virals

Recently there has been a report regarding the use of an anti-rhinoviral agent known as Plecoranil.This anti-viral binds to a hydrophobic pocket of the VP1, the major shell protein for the

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rhinoviruses, thereby preventing the virus from exposing its RNA and also prevents the virus fromattaching itself to the host cell [210]. The rhinovirus 3C protease inhibitors, Ruprintrivir [211] andsoluble recombinant ICAM-1 Tremacamra [212], have shown promising results but they arecurrently not widely available.

Conclusions

The role of bacteria and viruses in non-CF bronchiectasis is not presently fully understood.Through necessity, evidence from studies in CF and COPD is used and applied to bronchiectasis.More research using both conventional microbiological techniques as well as newer moleculardiagnostic approaches, is urgently required to address a number of important questions in non-CFbronchiectasis. 1) What is the cause of infective exacerbations? 2) What is the role of anaerobicbacteria and how do normal commensal bacteria interact with pathogenic bacteria? 3) How can weclear chronic infection? 4) What proportion of exacerbations is triggered by viral infection?5) How do viruses influence bacterial behaviour in chronically infected airways?

A greater understanding of bacterial communal behaviour and their interaction with epithelial

cells and viruses will be critical in further developments in the management of non-CFbronchiectasis.


J.E. Foweraker received a consultancy fee from Novartis Pharma AG for advice on a submission tothe European Medicines Agency for licensing of Tobramycin inhaled powder and a consultancy fee from Gilead Sciences International Ltd for advice on an application to European MedicinesAgency for licensing of Aztreonam lysine.

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respiratory syncytial virus glycoprotein. J Med Microbiol 2007; 56: 1133–1137.197. Stark JM, Stark MA, Colasurdo GN, et al. Decreased bacterial clearance from the lungs of mice following primary

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198. Chattoraj SS, Ganesan S, Jones AM, et al. Rhinovirus infection liberates planktonic bacteria from biofilm

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199. Fleming DM. The impact of three influenza epidemics on primary care in England and Wales.

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from respiratory syncytial virus infection in high risk infants. Paediatrics 1998; 102:

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randomised controlled trial. Neuraminidase Inhibitor Flu Treatment Investigator Group. Lancet 2000; 355:

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203. Randomised trial of efficacy and safety of inhaled Zanamivir in the treatment of influenza A and B virus

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1998; 352: 1877–1881.

204. Hayden FG, Treanor JJ, Betts RF, et al. Safety and efficacy of the neuraminidase inhibitor GG167 in experimental

human influenza. JAMA 1996; 275: 295–299.

205. Jefferson T, Jones M, Doshi P, et al. Neuraminidase inhibitors for preventing and treating influenza in healthy

adults: systematic review and meta-analysis. BMJ 2009; 339: b5106.

206. American Academy of Pediatrics Committee on Infectious Diseases. Use of ribavarin in the treatment of

respiratory syncytial virus infection. Pediatrics 1993; 92: 501–504.207. Smith DW, Frankel LR, Mathers LH, et al. A controlled trial of aerosolized ribavirin in infants

receiving mechanical ventilation for severe respiratory syncytial virus infection. N Engl J Med 1991; 325:

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208. Turner RB, Wecker MT, Pohl G, et al. Efficacy of tremacamra, a soluble intercellular adhesion molecule 1, for

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209. Suzuki T, Yamaya M, Sekizawa K, et al. Erythromycin inhibits rhinovirus infection in cultured human tracheal

epithelial cells. Am J Respir Crit Care Med 2002; 165: 1113–1118.

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into genus phylogeny and susceptibility to antiviral capsid-binding compounds. J Virol 2004; 78:

3663–3674.

211. Hayden FG, Turner RB, Gwaltney JM, et al. Phase II, randomized, double-blind, placebo-controlled studies of

ruprintrivir nasal spray 2-percent suspension for prevention and treatment of experimentally induced rhinovirus

colds in healthy volunteers. Antimicrob Agents Chemother 2003; 47: 3907–3916.

212. Turner RB, Wecker MT, Pohl G, et al. Efficacy of tremacamra, a soluble intercellular adhesion molecule 1, for

experimental rhinovirus infection: a randomized clinical trial. JAMA 1999; 281: 1797–1804.

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Chapter 7

Allergic

bronchopulmonary

aspergillosis and other

fungal diseasesB. Hilvering*, J. Speirs # , C.K. van der Ent # and J.M. Beekman #

Summary

Fungal spores are ubiquitously present in the air. Inhalation of these spores by humans causes disease in susceptible patients;most prevalent are invasive aspergillosis and allergic broncho-pulmonary aspergillosis (ABPA). This chapter provides an

overview of the pathogenecity, clinical appearance, diagnosisand treatment of ABPA.ABPA is a hypersensitivity lung disease limited to patients

with asthma or cystic fibrosis (CF) with a prevalence of 1–2%and 2–15%, respectively within these groups. It is triggeredby the exposure to Aspergillus fumigatus. Although it isnot clear what initiates this hypersensitivity response, poly-morphisms in genes that drive innate and adaptive immunemechanisms as well as loss-of-function mutations in the CFtransmembrane conductance regulator (CFTR) are associated

with ABPA development. The chronic inflammatory conditionsin ABPA eventually result in airway remodelling and functionalimpairment.

The diagnosis of ABPA is based both on clinical symptoms,laboratory testing and diagnostic imaging. Treatment consistsof a two tiered approach, glucocorticoids to control immuno-logical activity and antifungal agents to suppress fungal load.

Keywords: ABPA, aspergillosis, Aspergillus fumigatus, CFTR,hypersensitivity

*Dept of Pulmonology, University Medical Center Utrecht, and#Dept of Paediatric Pulmonology,Wilhelmina Children’s Hospital,University Medical Center Utrecht,Utrecht, The Netherlands.

Correspondence: C.K. van der Ent,

Dept of Paediatric Pulmonology,University Medical Center Utrecht,Lundlaan 6, 3584 EA Utrecht, theNetherlands, [email protected]

Eur Respir Mon 2011. 52, 97–114.Printed in UK – all rights reserved.Copyright ERS 2011.European Respiratory Monograph;

ISSN: 1025-448x.DOI: 10.1183/1025448x.10003710

Humans continuously inhale fungal spores. Only some fungal species cause invasive, allergic ortoxic disease, most prevalent of which are invasive aspergillosis in immunocompromised

patients and allergic bronchopulmonary aspergillosis (ABPA) in asthmatics and patients withcystic fibrosis (CF). This chapter provides an overview of the current knowledge concerning the

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role of fungi in the pathogenesis of bronchiectasis and describes the clinical appearance,immunological background, diagnosis and treatment of ABPA.

Centrally located, cylindrical bronchiectasis is a major characteristic of ABPA; however, 5–25% of patients with ABPA are diagnosed without the presence of bronchiectasis [1–3]. ABPA ispredominantly observed in asthmatic and CF patients. Its prevalence among asthmatics and CFpatients is 1–2% [4] and 2–15% [5–11], respectively.

In patients with ABPA, Aspergillus fumigatus antigens provoke a strong allergic reaction,characterised by the dominance of T-helper cell (Th) type 2 mediated responses, high numbers of eosinophils, a high total immunoglobulin (Ig)E level and high levels of Aspergillus specific IgE andIgG levels. Although it is not clear what initiates this hypersensitivity response, polymorphisms ingenes that drive innate and adaptive immune mechanisms as well as loss-of-function mutations inthe CF transmembrane conductance regulator (CFTR) are associated with ABPA development.The chronic inflammatory conditions in ABPA eventually result in airway remodelling, which ischaracterised by mucoid impaction, bronchial inflammation and obstruction. When left untreatedfibrosis bronchiectasis and eventually respiratory insufficiency are the final pathophysiologicalstages in this remodelling process.

The diagnosis of ABPA is complex and difficult to discriminate from chronic inflammatory episodes already observed in patients with asthma or CF. It has been estimated that on average10 years elapse between the onset of ABPA and its eventual diagnosis [12]. Criteria for thediagnosis ABPA in asthmatics include a history of asthma with immediate skin reactivity, elevatedserum IgE, precipitating antibodies against Aspergillus sp., peripheral blood eosinophilia, currentor previous infiltrates on chest radiographs and central bronchiectasis on high-resolutioncomputed tomography (HRCT) scans. CF patients are chronically exposed to multiple micro-organisms and discrimination of ABPA is difficult in these patients. The main diagnostic criteriaare similar to those described above, except for higher total IgE levels.

ABPA treatment aims at reducing the fungal burden and dampening the immune response.Antifungal agents are effective in reducing IgE levels and improving clinical outcome within a 16-week period; however, their long-term clinical effects are unknown [13]. The role of antifungalagents in the eradication of A. fumigatus hyphae is limited. Immune suppression is mainly achieved by oral glucocorticoid therapy that reduces the total serum IgE levels and correlateswith a reduction in symptoms and radiological findings. However, the long-term use of steroidsis associated with serious side-effects. Therapy that targets individual components of thehypersensitivity reaction is being developed and tested. The identification of crucial immuno-logical components and associated molecular targets is essential for the design of novel drugs.

Bronchiectasis due to other fungal disease is mainly limited to the immunocompromised host.

Only limited studies are available on the role of fungi in otherwise healthy subjects. Both groupsare briefly summarised in this chapter.

Figure 1 shows the structure and appearance of A. fumagatis under light microscopy.

History and epidemiology of ABPA

In 1952, HINSON et al. [14] provided the term ABPA for the description of three patients whosuffered from pulmonary eosinophilia in the UK, and in 1969 ABPA was first reported in the USA.In 1971, immunoserological features were discovered that supported hypersensitive immune

reactivity as a disease mechanism in ABPA. From that time onwards the diagnostic possibilitiesrapidly improved and in the early 1980s ABPA was reported throughout the world.

Still, the true population prevalence of ABPA remains highly speculative: ABPA was notacknowledged by the World Health Organization (WHO) as a disease entity in their 2007International Classification of Disease (ICD-10) [15] and the diagnostic criteria for ABPA vary greatly within international medical societies. It has been generally assumed that there is an

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estimated population ABPA prevalence of 1–2% inasthmatics [16, 17]. Overviews on the prevalence of ABPA show a spectre of 1% prevalence in the generalpopulation of asthmatics to 38.6% in patients withacute severe asthma [18].

In patients with CF the prevalence is estimated to be

1–15% [16, 19]. NOVEY [16] found an average of 7%among a total of 1,096 patients, taken from eightstudies. Despite the differences in diagnostic criteria,laboratory methodology, demographical and geogra-phical features, the range of prevalence was narrow inthese studies ranging from 3–11%. MASTELLA et al.[20], on behalf of the European Registry of CysticFibrosis, reported data for 12,447 patients with CFin nine European countries. The overall prevalenceamong the European CF patients was found to be7.8%, with a range of 2.1% in Sweden and 13.8% inBelgium. Age was found to be an important factor; inthe group aged ,6 years the prevalence was 6% and astable 10% thereafter [20].

Bronchiectasis and ABPA

Bronchiectasis is a morphological disorder, defined as the irreversible dilatation of the cartilagecontaining airways or bronchi. Approximately half of the patients with bronchiectasis is classifiedas having idiopathic bronchiectasis. In 7–8% of patients with bronchiectasis, ABPA is the causative

factor [21, 22]. ABPA can be subclassified into three groups based upon radiological featuresindicating the presence or absence of central bronchiectasis and other radiological features.Approximately 75–95% of ABPA patients display both centrally located, cylindrical bronchiectasis(ABPA-CB) with or without other radiological features (ABPA-CB-ORF). The remaining 5–25%of the patients with ABPA are diagnosed without the presence of bronchiectasis, in these patientsthe diagnosis is based on seropositivity (ABPA-S) [1–3].

The presence of central bronchiectasis is associated with disease severity. The small group of patients with ABPA-S appear to suffer from a less aggressive form of the disease when comparedwith ABPA-CB and ABPA-CB-ORF patients. Whether ABPA-S is able to progress into ABPA-CBor whether it is a pathogenetically different form of the disease is unclear. In a 3-year prospective

cohort study in 11 patients, KUMAR and CHOPRA [23] described better lung function and a lowernumber of exacerbations in the ABPA-S group compared with an ABPA-CB control group.GREENBERGER et al. [24] included 28 patients in a 2-year prospective cohort study and founddifferent immunological parameters in the ABPA-S group compared with the ABPA-CB group.The study found significantly lower serum specific anti-A. fumigatus IgG subclasses in patientswith ABPA-S, and a trend towards lower levels of total serum IgE and specific anti- Aspergillus IgEand IgA [24]. The radiological differences between the groups are, therefore, also reflected by clinical and immunological differences. The question remains whether early recognition andtreatment of ABPA-S can prevent progression into ABPA-CB [23].

Pathogenesis of ABPA

The pathophysiological mechanisms underlying the development of ABPA are still poorly understood, but clearly share important immunological mechanisms with other hypersensitivity diseases. ABPA primarily develops in patients with asthma or CF, and is caused by an Aspergillus -driven strong hypersensitivity response [25]. Immunological features include highly elevated levels

Figure 1. Light microscopy of Aspergillus

fumigatus hyphae. The stalk is called ahypha, the end of the hypha is swollen and

small strings emerge from it called philiades.

Chains of conidia (seen as small blue balls)emerge from the philiades. Reproduced

with permission from K. Makimura (Teikyo

University Institute of Medical Mycobiology,

Tokyo, Japan; personal communication)and the Pathogenic Fungi Database (www.

pfdb.net/).

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of total IgE and Aspergillus -specific IgE and IgG, increased eosinophil numbers, and a Th2-dominatedantigen-specific CD4+ T-cell response. Hypersensitivity to Aspergillus and colonisation by Aspergillus appear to be required but are not sufficient to develop ABPA alone. Between 31 and 59% of CFpatients display sensitisation towards Aspergillus and up to 40% are colonised; however, only 1–10%of CF patients develop ABPA [26]. It appears that unique characteristics within Aspergillus itself incombination with patient-specific environmental and genetic factors facilitate the chroniccolonisation and development of a deteriorating immune response, which ultimately induces the

irreversible airway remodelling associated with fibrosis, pulmonary obstruction and bronchiectasis.

A. fumigatus virulence

Fungal spores (fig. 2) or conidia are ubiquitously present in our environment. A cubic meter of airtypically contains approximately 104–105 conidia, predominantly of the Cladosporium andAlternaria genera , and of a lesser amount Aspergillus and Penicillium. The genus Aspergillus consistsof 250 subspecies of which A. fumigatus is considered the most prevalent airborne fungal humanpathogen, its conidia are present at approximately 1–100 m-3 air [27]. A. fumigatus causes lifethreatening, invasive disease in immunocompromised patients and is associated with multiple

hypersensitivity responses including allergic asthma, hypersensitivity pneumonitis and ABPA [28].Many molecular subtypes of A. fumigatus exist, 85% of analysed A. fumigatus in air samples wereunique; however, in general none of these subtypes were found to be selectively enriched inpatients suggesting that most subtypes are equally pathogenic [29, 30]. The development of novelantifungal reagents may, however, select for some subtypes [31, 32]. The presence of specificsubtypes of A. fumigatus in ABPA remains unknown, but these may be prime candidates to study ABPA-related disease mechanisms.

In recent years insights into the mechanisms by which A. fumigatus regulates its pathogenicpotential or virulence have progressed significantly. These mechanisms regulate the rapid growthcharacteristics of A. fumigatus at 37uC (A. fumigatus conidia germinate within 4–5 hours onnutrient rich media in vitro ), the overall mechanical fitness of conidia to withstand environmentalpressure, and its capacity to extract nutrients of dead organic matter for growth. Selectivemechanisms have also co-evolved. These selective mechanisms directly impair the epithelial barrierfunction and host immune defence, facilitating its infection.

The particularly small size of a A. fumigatus conidia range between 1 mm and 3 mm, thereby facilitating its ability to be airborne and allowing it to reach the alveolar spaces upon inhalation.

The cell wall of A. fumigatus conidia consists of a thick internal layer of structural polysaccharides enriched forbranched b(1,3)/(1,6) glucans linked to chitin as

observed in most fungi [33, 34]. Additional bonds tothis backbone are species specific, in the case of A. fumigatus this core polysaccharide backbone isfurther linked to galactomannan and linear b(1,3)/(1,4)-glucans. This large polysaccharide complex isembedded in a cement-like mixture consisting of a1,3-glucan, galactomannan and polygalactosamine. A thinhydrophobic protein layer, termed surface hydropho-bin, is composed of cross-linked proteins (includingRodA) that form a regular pattern of rodlet structures

and melanin that confers pigment, which furthershields and protects the polysaccharide shell.

Germination initiates an asexual developmental growthprogramme. It starts with conidial swelling followed by a polar growth programme that results in the protru-sion of an elongating germ tube, termed hyphae, from

Figure 2. Low temperature scanning

electron microscopy image illustrating a tuftof Aspergillus spores arranged in rows. A

spore is approximately 1 mm in size (M.H.

Umar, Maasstad Hospital, Rotterdam, the

Netherlands; personal communication).

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the conidium cell [35]. Hyphae are covered by a newly synthesised polysaccharide coat without thetypical protein coat present on conidia [35]. Simultaneously with polar growth comes nucleardivision by mitosis, resulting in further elongating hyphae with each cycle. In immunocompro-mised patients, Aspergillus grows into large hyphal networks termed mycelia and formsextracellular matrices termed biofilms that contain a1,3-glucan, galactomannan and galactosa-minogalactan, and possibly other components that promote growth [36]. Interestingly, germina-tion of A. fumigatus conidia is increased compared with Aspergillus flavus and Aspergillus niger at

37uC but not at 20uC [37]. This increased growth rate at 37uC likely contributes to the prevalenceof A. fumigatus in fungal diseases, such as ABPA.

A. fumigatus expresses multiple factors to evade host immune defence mechanisms, which in totalcontribute to the virulence of A. fumigatus in humans. These factors may be part of the growthcycle of A. fumigatus , but may also be uniquely expressed as secondary metabolites during specificphases of growth. For example, the binding of conidia to various extracellular matrix (ECM)proteins prevents its mucociliairy clearance and the oxidative mechanisms of phagocytes arecounteracted by the production of superoxide dismutases, mannitol and three types of catalases.A range of other toxins and proteases further inhibit immune responses and promote epithelialcell penetration including ribotoxin [38], phospholipases [39], haemolysins, gliotoxins, metal-loproteinase, alkaline proteinase and elastase [40].

Interestingly, when comparing fungal proteases of A. fumigatus with those of Alternaria alternata and Cladosporium herbarum, KAUFFMAN et al. [41] reported an increase in the activity of A. fumigatus -derived proteases, as indicated by the shrinking and desquamation of epithelial cellsand pro-inflammatory cytokine production. Although the role of isolated components fromA. fumigatus in conferring virulence as a human pathogen remains difficult to establish, it is clearthat their combined activity contributes to the strong association of A. fumigatus with fatalhuman diseases.

Innate mechanisms underlying ABPA

The innate defence mechanisms involved in the clearance and inflammatory response toA. fumigatus , and how these may impact on the development of ABPA will be discussed here. Themajority of conidia are cleared without inflicting a strong inflammatory response associated withtissue destruction. Most inhaled conidia are efficiently trapped by mucus and removed by mucociliary clearance systems that are affected in CF and asthma patients. Nevertheless, ABPA isgenerally not observed in patients with primary ciliary dyskinesia in which impaired mucociliary clearance leads to the accumulation of mucus and primarily bacterial infections, suggestingadditional mechanisms contribute to the development of ABPA [42].

Beyond the mucociliary system, resident cells of the lungs, such as alveolar macrophages (AM) andtype II pneumocytes, destroy conidia by phagocytosis and the production of reactive oxygenspecies (ROS) upon activation of the membrane-bound NADPH-oxidase complex. It was recently shown that RodA in the protein coat surrounding conidia inhibits the inflammatory response toconidia by masking the highly immunogenic polysaccharide cell wall [43]. This may promotesurvival of conidia by escaping host immunity, but may also be beneficial to the host by limitinginflammatory responses upon inhalation of conidia.

However, during germination the extending hyphae expose their polysaccharide wall and start toproduce metabolites that trigger a strong inflammatory response. Pattern recognition receptors,

e.g. Toll-like receptors (TLRs) and carbohydrate-binding proteins termed C-type lectins, areexpressed by lung epithelial and resident immune cells, such as AM and dendritic cells (DCs),which recognise the b-glucans, chitin and galactomannan of the cell wall. Controversy still existsover the exact functional role of individual TLRs in the recognition of fungi, but it appears thatTLR2, TLR4 and TLR9 do signal in a fungal morphotype-specific manner [44]. Activation of TLR2and inhibition of TLR4 signalling during hyphal growth has been proposed to promote thedevelopment of a Th2 response [45, 46].

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In addition to TLRs, members of the C-type lectin family, e.g. the mannose receptor, DC-specificintercellular adhesion molecule-grabbing nonintegrin (DC-SIGN), Dectin-1, and Dectin-2,recognise carbohydrate structures of the fungal wall and play an important role in fungalrecognition, killing, and inflammatory signalling. Dectin-1 binds b-(1,3)-glucan and is prevalenton neutrophils, AM and DC. Neutrophils are the first cells to enter an inflammatory site and areshort-lived phagocytic effector cells. Neutrophils produce ROS and release proteolytic enzymes,upon apoptosis their DNA traps pathogens but also increase mucus viscosity [47, 48]. Mice

lacking Dectin-1 are highly susceptible to A. fumigatus infection; their macrophages and DCproduce low levels of inflammatory cytokines and have limited recruitment of neutrophils to thesite of infection with reduced killing capacity [49].

Triggering these pattern-recognition receptors induces the release of multiple inflammatory networks that recruit cells from the blood to the infected area, and play a crucial role in shapingthe adaptive immune response at later stages [50–52]. Human polymorphisms in these systemscan affect fungal load, growth properties and the balance of inflammatory mediators produced by innate cells that can impact on the quality and quantity of the adaptive response. ABPA iscorrelated with polymorphisms in TLR9 [53]. The mechanism by which TLR9 predisposes to

ABPA in humans remains uncertain; however, pulmonary hypersensitivity induced by A. fumigatus in TLR9 -/- mice is significantly reduced [54]. DCs of these mice have lower Dectin-1levels and produce low amounts of interleukin (IL)-17, which was associated with pulmonary infection of A. fumigatus . Multiple polymorphisms in other innate recognition systems includingTLR2 and TLR4 and humoral pattern recognition factors, such as mannose binding lectin andsurfactant protein A, have also been associated with ABPA and other different types of fungaldiseases [55–59].

Collectively, it is clear that a complex multi-layered innate response to A. fumigatus has evolved toprevent infection and subsequent invasive disease. Genetic variations in innate systems that impacton pathogen recognition, fungal infection and induction of hypersensitivity responses have been

associated with fungal diseases including ABPA. The extent to which genetic variation within thesesystems affects the development of ABPA in subgroups of CF or asthmatic patients requiresfurther attention and may have prognostic value for patient subgroups.

Adaptive immunity in ABPA

DCs are specialised cells that take up antigens at local inflammatory sites and then migrate todraining lymph nodes or bronchus associated lymphoid tissue (BALT) where they activate naıveT-cells by presentation of antigenic peptides in the context of major histocompatibilty complex (MHC) [50]. Upon activation of naıve Th cells, these cells acquire distinct cytokine-secreting

properties that impact on the developing immune response. Multiple subsets of committedantigen-experienced Th cells are recognised including Th1, Th2, Th17 and induced T-regulatory (T-reg) cells [60]. In general, interferon-c producing Th1 and IL-17 producing Th17 subsets areimportant inflammatory cells associated with cell-mediated immunity against viral infections andintracellular bacteria, and are associated with multiple autoimmune diseases. IL-4 producing Th2cells are typically associated with strong immune responses against large extracellular organismsthat cannot be cleared through phagocytosis, such as intestinal parasites, and are associated withallergic diseases and ABPA in humans. Induced T-reg cells and natural T-reg cells are important todampen immunological responses by the production of IL-10 and transforming growth factor(TGF)-b [61].

Th responses are skewed towards Th2 in ABPA as indicated by in vitro lymphocyte responsesagainst secreted proteins from A. fumigatus and animal models [26, 62–66]. Th1 and Th17responses against A. fumigatus appear protective against hypersensitivity and are associated withclearance of Aspergillus [67–69]. Why ABPA patients mount such a vigorous Th2-response is notknown and remains a key question. Activation of specific pattern recognition receptors andcytokine receptors at the site of inflammation induces DCs to express surface molecules and

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cytokines, which help to commit naıve Th cells; however, T-cell intrinsic factors, such as T-cellreceptor (TCR) avidity for its antigen, also appear important.

Recently, epithelial products such as IL-25 and thymic stromal lymphopoietin (TSLP) have beenshown to alter DCs function and subsequent Th responses [70–72]. TSLP stimulated DCs fromABPA patients use ligand OX40 to potently induce Th2 responses [71]. Other ABPA-associatedpolymorphisms in genes, e.g. TLR9, IL-4R a subunit and the IL-10 promotor, may all affect DC

maturation and or induction of Th differentiation, but these proteins are expressed by many cellsand thus it remains difficult to pinpoint at which level these polymorphisms affect disease [73].

TCRs that bind with low affinity to their cognate antigen may also confer Th2 properties in ABPA.Variants of human MHC class II, such as HLA-DR2 and HLA-DR5 alleles, are associated withABPA and promote the expansion of T-cells with selective ab TCR chains. Although expressionof these MHC class II variants is not sufficient for ABPA disease, peptides of a dominant allergenof A. fumigatus , termed Asp f1, are presented by these molecules and are recognised by low-affinity, TCR-expressing Th2-skewed cells [74]. Other MHC class II alleles also appear to protectagainst ABPA.

Th2 cells and their cytokines play a crucial role in B-cell class switching and the recruitment of IgE-responding innate cells such as eosinophils, basophils and mast cells. Early studies indicatethat supernatants of lymphocytes incubated with A. fumigatus antigens regulate IgE production by B-cells [74]. Cytokines, such as IL-4, IL-5 and IL-13, by Th2 cells facilitates B-cell class switchingto IgA and IgE in BALT, and induce the production and recruitment of eosinophils to theinflammatory site [19]. IgE levels are quantitatively higher in ABPA compared with other atopicconditions, though little is known about the width of the antibody response against A. fumigatus and possible bystander antigens including self antigens. However, recent evidence indicates theexistence of a Th2-mediated immune response without the presence of IgE [75]. To place thiscontradiction into perspective, data from a recent study indicated that out of 66 proteins present

in the cytosol of A. fumigatus , which were recognised by pooled serum of ABPA patients, 63 weretargeted by IgE and only three by IgG antibodies [76]. The prevalence of A. fumigatus -specific IgEover IgG antibodies suggests BALT to be a primary site for development of high-specificAspergillus IgE and not the peripheral lymphoid system.

Upon comparison of atopic and ABPA patients, ABPA B-cells were found that expressed higherlevels of the low-affinity IgE receptor CD23 and the co-stimulatory molecule CD86 that is crucialfor positive reinforcement by Th cells, a phenotype associated with in vitro IL-4 responsiveness[77]. Indeed, polymorphisms in IL-4Ra have been found to be enriched within ABPA patients incomparison with non-ABPA patients. Furthermore, CF patients with ABPA are more sensitive toIL-4 than CF patients without ABPA, a finding that was not observed for IL-13 [78, 79].

These antibodies trigger hypersensitivity responses by interacting with specialised innate immunecells. IgA and IgE-responsive granulocytes, such as eosinophils, basophils, and mast cells areactivated by the Th2 response and recruited to the inflammatory site by a network of solublemediators and cell-surface molecules [80]. Ligation of IgE on mast cells releases histamine andchemokines such as leukotriene B4 and platelet-activating factor, which induce smooth musclecontraction, vascular permeability and attract eosinophils. RANTES (regulated on activation,normal T-cell expressed and secreted), eotaxin and monocyte chemotactic protein (MCP)-3 areother important chemoattractants for eosinophils. The receptor for eotaxin, chemokine receptor 3(CCR3) is selectively expressed by Th2, eosinophils and basophils, and is upregulated by IL-4.

Th2-derived IL-5 is essential for increased eosinophil production from the bone marrow and theiractivation but appears dispensible for A. fumigatus -induced hyperreactivity in mice [81].Nevertheless, these cells are a prominent feature of ABPA and are highly present in bronchialalveolar lavages suggesting their products to inflict tissue damage under chronic conditions [19].Chemokines are implicated in various allergic conditions; however, their exact role in ABPArequires further refinement as the blockade of these by therapeutics may control the inflammatory cellular composition and local tissue destruction.

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It has long been recognised that mucosal-associated immunity, especially in the gut, appears to beregulated by T-lymphocytes expressing IL-10 and or TGF-b [82]. Recently, CF patients colonisedby A. fumigatus were shown to have increased levels of FoxP3-positive T-reg cells that expressedhigher levels of surface TGF-b upon A. fumigatus stimulation, and confer tolerance to oralantigens in mice [61, 71]. The role of IL-10 producing T-reg cells (sometimes termed Tr1 cells) inABPA is not clear; however, IL-10 promotor polymorphisms have been associated with fungaldiseases and ABPA [73]. Adoptive transfer of T-reg cells is effective in lowering inflammatory

conditions in multiple animal models suggesting that modulation of the number and activation of these cells in humans may control excessive inflammation in ABPA.

In conclusion, inflammatory mediators of Th2 cells including IL-4, IL5 and IL-13 play a dominantrole in the induction and maintenance of the hypersensitivity response in ABPA. These pro-mote IgE and IgA isotype switching and attract typical innate effector cells associated withhypersensitivity responses such as eosinophils, basophils and mast cells. Genetic variation in thesepathways predispose for ABPA; however, ranking these for their role in ABPA disease developmentwill prove difficult considering the impact of environmental variables and limited patientnumbers. Based on homology with other hypersensitivity disorders, the mechanisms that underlie

Th differentiation in ABPA can begin to be understood; however, the characterisation of Thsubsets and their role in ABPA development has only just started.

CFTR-related immunological disease mechanisms in ABPA

In general, the immune mechanisms in CF are normal; however, there is evidence to support thatABPA, specifically, may also result from the abnormal function of CFTR in immune cells next to theepithelial cells. The association between CF patients and allergic disease was reported in 1949 [83].CF patients have mutations in CFTR that encodes an adenosine triphosphate (ATP)- and cyclicadenosine monophosphate (cAMP)-regulated anion channel that regulates the composition of excretions [84]. CFTR in the lung epithelium regulates the air–surface liquid layer that underlies themucus layer, which impacts the mucociliary clearance and functions of humoral components [85].

CFTR is expressed in multiple other tissues including the immune system, suggesting that thehyperinflammatory status of CF patients that was previously believed to be secondary to infectionmay result from a dysregulated immune response caused by a CFTR mutation [86–89]. Geneticstudies in mice support a role for CFTR in macrophages, DCs and lymphocytes [90, 91]. In humaninnate cells the impaired bacterial clearance by phagocytes has been observed; however, thecapacity of these cells to present antigens to T-cells has not been thoroughly assessed [92, 93].MULLER et al. [91] reported that CFTR deficiency in mice provokes a stronger hypersensitivity response to A. fumigatus , and a shift from a predominant cytokine profile of IL-5 to IL-4. Recently,

CD3 lymphocytes were implicated in the hypersensitivity response towards A. fumigatus by adoptive transfer experiments [94]. Conditional knockouts that lack CFTR in lymphocytes haveenhanced basal and A. fumigatus -induced IgE levels, further supporting that CFTR is functional inmurine CD4+ lymphocytes by limiting Th2-skewing.

Asthmatic non-CF individuals with ABPA frequently carry a mutant CFTR allele [95–98]. A recentstudy, which involved the extensive CFTR sequencing of ABPA patients with normal sweatchloride levels and pancreatic function, found that the CFTR mutation frequency in patients withABPA was approximately 48 higher compared with the general population [98]. Whether certainCFTR mutations specifically cluster with ABPA remains to be seen, and as this is difficult to study due to low patient numbers it remains undetermined. The strong correlation of ABPA with CFTR heterozygocity is remarkable, as it has been generally accepted that approximately 20% residualfunction is sufficient for epithelial functioning. This may point out that other tissues are morestrongly affected by CFTR deficiency, but cannot rule out epithelial involvement. The hypothesisthat CFTR mutant lymphocytes are intrinsically Th2-primed, as may be expected from micestudies, requires further thorough investigation and should carefully address confounding factors,such as genetic background, infectious status and therapeutic regimen.

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Summary

To summarise, ABPA is mostly prevalent in CF patients compared with a small percentage of asthma patients, and is a result of complex interactions between the invasive pathogenA. fumigatus and the human immune system. Th2-skewing of Th cells followed by a stronghumoral IgE response and activation of IgE-responding effector cells are clear hallmarks of ABPA.To date, genetic variation in CFTR itself appears to be the strongest genetic factor associated with

ABPA, also in asthmatics. A. fumigatus -driven hypersensitivity mouse models reflecting ABPAstrongly support a role for CFTR within the T-cell compartment [91, 94]. The strong relationshipbetween ABPA and CF may, therefore, not only result from impaired epithelial functioning butmay also result from lymphocyte defects that only become apparent upon strong Th2 stimuli

Infectious sitea)

b)

c)

d)

Infectious siteMycelium

Conidium

Immune inhibitoryprotein-rich outer shell:

RodA and melanin

Non-inflammatoryclearance;

phagocytosisCFTR-dependent

mucociliary system

Inflammatory clearanceby resident cells and

attracted innate cells;CFTR-dependent killing?

Activation of patternrecognition receptorsin lung epithelium andinnate immune cells

Cellular damage;release of

danger signals

Stimulationof lgE-responsive

eosinophils

Th2 cells

Naïve T-cells

Lymphoid tissueTissue-derived dendritic cells

Naïve B-cells

lgE+secretingplasma cell

β-glucansChitinGalactomannan

Aspergillus fumigatus

EpitheliumToll-like receptors

IL-25, TSLP, ATP

C-type lectins

Dendrtic cell

Phagocytosis andantigen processing

NADPHoxidase

MHCclass II

Endosomalproteases

Fungus-associatedinflammatory signalling

Fungus-associatedinflammatory signalling

Dendritic cell

Lymphoid tissue

Antigen presentation Co-stimulation

MHC

class II

MHCclass IIB-cell

BCR

CD23 lgE classswitching

Th2 skewing

TCR

TCR

IL-25, IL-4CD40

CD40L

CD40

CD40L

T-helper cell

Eosinophil

Mast cell

Basophil

IL-4IL-5IL-13

Induction of Thskewing conditions

Nucleus

CFTR inhibits skewingtowards Th2 cells?

Exposure of cell wallpolysaccharides:β-glucan,

chitin, galactomannan

Release of toxins,proteases and other

secondary metabolites

Germination

Protruding

hyphae

T L R - 4

T L R - 2

D e c t i n - 1

D C - S I G N

M a n n o s e

r e c e p t o r

T L R - 9

Figure 3. Immunopathogenesis of allergic bronchopulmonary aspergillosis. a) Aspergillus fumigatus asexual life

cycle and the interactions of innate epithelial and immune components with dormant conidia or germinating

conidia at the site of infection. b) Interactions between adaptive components of the immune system in thelymphoid tissue showing proven or possible (&) involvement of cystic fibrosis transmembrane conductance

regulator (CFTR). Detailed schematic representation of molecular interactions between A. fumigatus and various

immune cell subsets at c) the infectious site or d) lymphoid tissue are shown. Local priming of dendritic cells(DCs) by fungus and epithelial-derived products is important for T-helper (Th) cell skewing. DCs at the lymphoidtissue stimulate naı ¨ve Th cells by upregulation of major histocompatibilty complex (MHC) class II antigen

complexes in combination with specific co-stimulatory pathways that activate Th2 cells. These facilitate

immunoglobulin (Ig)E class switching of B-cells and the activation and recruitment of eosinophils, basophils and

mast cells. TLR: toll-like receptors; TSLP: thymic stromal lymphopoietin; IL: interleukin; ATP: adenosinetriphosphate; TCR: T-cell receptor; BCR: B-cell receptor.

h

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associated with A. fumigatus . Therefore, it appears that next to environmental factors such asnutritional status, co-infection and long-term immune suppression, genetic variations in thesystems underlying A. fumigatus recognition, clearance and Th2 skewing may also drive patient-specific ABPA susceptibility. The identification of ABPA-related disease mechanisms will becrucial for future development of therapeutics that control immune-related tissue destructionwithout impairment of fungal clearance. Figure 3 illustrates the immunopathogenecity of ABPA.

Clinical features and diagnostic approach

Patients with ABPA typically present with symptoms such as a low-grade fever, productive cough,bronchial hyperreactivity, chest pain, wheezing, haemoptysis and expectoration of brownishsputum plugs. Sometimes patients are asymptomatic and diagnosed during routine screening testsin patients with asthma or CF. Physical examination can reveal wheezing or coarse crackles onauscultation, clubbing of the fingers in 15% of patients and complications such as pulmonary hypertension and/or respiratory failure [99, 100]. The diagnostic criteria for patients with asthmaare summarised in table 1. Because the primary disease symptoms in patients with CF can closely

resemble ABPA, adapted criteria for ABPA have been formulated within this patient category (table 2). In CF, ABPA is diagnosed in the presence of the following: 1) acute or subacute clinicaldeterioration not attributable to another aetiology; 2) total serum IgE concentration of .500 IU?mL-1; 3) immediate cutaneous reactivity to A. fumigatus or in vitro demonstrationof IgE antibody to A. fumigatus ; and 4) either precipitins to A. fumigatus or in vitro demonstrationof IgG antibody to A. fumigatus or new or recent abnormalities on radiological tests (CT scan orchest radiograph).

Skin testing

In patients with bronchial asthma Aspergillus skin testing is recommended for screening purposes.Intradermal injection is more sensitive in comparison to the skin-prick test [64, 102, 103].A positive reaction to recombinant antigens of A. fumigatus termed rAsp f 4 and/or 6 reached asensitivity of 86.8% (95% CI 73.5–100%) and a specificity of 92% (95% CI 83.9–100%) in a study with 50 CF patients [102]. Of those 50 patients, 12 suffered from ABPA, 21 were sensitised forA. fumigatus and 17 were control patients. However, less promising results were obtained by DE OLIVEIRA et al. [104] who subjected 65 patients with asthma and a positive skin-prick test to

Table 1. Criteria for the diagnostis of allergic bronchopulmonary aspergillosis (ABPA) in patients with asthma

Criteria Minimal essentialcriteria

For ABPA central bronchiectasis

Asthma YesCentral bronchiectasis, inner two thirds of chest CT field Yes

Immediate cutaneous reactivity to Aspergillus sp. or A. fumigatus Yes

Total serum IgE concentration .417 kU?L-1 /1000 ng?mL-1 Yes

Elevated serum IgE and or IgG to A. fumigatus Yes

Chest roentgenographic infiltrates No

Serum precipitating antibodies to A. fumigatus No

For ABPA seropositive

Asthma Yes

Immediate cutaneous reactivity to Aspergillus sp. or A. fumigatus Yes Total serum IgE concentration .417 kU?L-1 /1000 ng?mL-1 Yes

Elevated serum IgE and or IgG to A. fumigatus YesChest roentgenographic infiltrates No

CT: computed tomography; A. fumigatus : Aspergillus fumigatus : Ig: immunoglobulin. Reproduced from [101]

with permission from the publisher.

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recombinant antigen testing. 19 patients tested positive for at least one recombinant antigen;however, only six of them met the classical criteria for ABPA.

Essential laboratory testing

Total serum IgE is the most important laboratory test for ABPA and is essential for the diagnosisand monitoring of the disease. Normal levels of total serum IgE in patients that do not receiveglucocorticoid therapy exclude ABPA as a diagnosis. In patients with asthma the total IgE levelsshould be .1,000 IU?mL-1, whereas in CF patients IgE levels of .1,500 IU?mL-1 can be detected.IgE levels are also used to monitor treatment. A reduction of 35–50% during treatment withsystemic steroids is considered as a remission [105].

Increased levels of specific serum IgE antibodies to A. fumigatus distinguish ABPA fromA. fumigatus hypersensitivity (AH), which is defined as a positive skin test, and other allergicconditions in asthmatics [106, 107]. The serum levels of Aspergillus -specific IgE are at least twice ashigh in ABPA compared with AH [108]. In patients with CF, specific serum IgE antibodies Asp f 3and Asp f 4 are specific for ABPA and not for Aspergillus hypersensitivity [109].

Supportive tests

The presence of serum precipitins, i.e . precipitating IgG antibodies, are supportive to the diagnosis

of ABPA [110, 111]. Peripheral eosinophilia is also regarded important in diagnosis; however, itmay have relatively low specificity or sensitivity [112]. A total of .1,000 cells?mL-1 has been set as acut-off value. The differential diagnosis of peripheral eosinophilia includes a range of otherdisorders such as tuberculosis, sarcoidosis, drug-induced eosinophilia and Churg–Strausssyndrome that should all be carefully ruled out. Sputum cultures are rarely used for diagnosingABPA as fungi can be prevalent in the lungs of many immunocompromised patients. Pulmonary function testing is not suitable as a diagnostic test and is only useful as a rough indicator for the

Table 2. Diagnostic criteria for allergic bronchopulmonary aspergillosis (ABPA) in cystic fibrosis (CF) patients

as proposed during the 2003 CF Foundation Consensus Conference (Bethesda, MD, USA)

Classic case

1. Acute or subacute clinical deterioration (cough, wheeze, exercise intolerance, exercise-inducedasthma, decline in pulmonary function, increased sputum) not attributable to another aetiology.

2. Serum total IgE concentration of .1000 IU?mL-1 (2400 ng?mL-1), unless the patient is receiving

systemic corticosteroids (if so, retest when steroid treatment is discontinued).

3. Immediate cutaneous reactivity to Aspergillus (prick skin test wheal of 3 mm in diameter withsurrounding erythema while the patient is not being treated with systemic antihistamines) or

in vitro presence of serum IgE antibody to A. fumigatus.

4. Precipitating antibodies to A. fumigatus or serum IgG antibody to A. fumigatus by an in vitro test.5. New or recent abnormalities on chest radiograph (infiltrates or mucus plugging) or chest CT

(bronchiectasis) that have not cleared with antibiotics and standard physiotherapy.Minimal diagnostic criteria

1. Acute or subacute clinical deterioration (cough, wheeze, exercise intolerance, exercise-induced

asthma, change in pulmonary function, or increased sputum production) not attributable to

another aetiology.2. Total serum IgE concentration of .500 IU?mL-1 (1200 ng?mL-1). If ABPA is suspected and the total

IgE level is 200–500 IU?mL-1, repeat testing in 1–3 months is recommended. If the patient is taking

steroids, repeat when steroid treatment is discontinued.3. Immediate cutaneous reactivity to Aspergillus (prick skin test wheal of 13 mm in diameter with

surrounding erythema, while the patient is not being treated with systemic antihistamines) or

in vitro demonstration of IgE antibody to A. fumigatus .

4. One of the following: precipitins to A. fumigatus or in vitro demonstration of IgG antibody to A. fumigatus ; or new or recent abnormalities on a chest radiograph (infiltrates or mucus plugging)

or chest CT (bronchiectasis) that have not cleared with antibiotics and standard physiotherapy.

Ig: immunoglobulin; A. fumigatus : Aspergillus fumigatatis ; CT: computed tomography. Reproduced from [19]

with permission from the publisher.

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severity of lung disease in general [113]. A promising serological test is for thymus and activation-regulated chemokine (TARC). Diagnostic accuracy was proven to be greater for TARC (93%) thanfor total IgE (74%), rAsp f 4 (75%) or rAsp f 6 (79%) in a small diagnostic study with 12 CFpatients with ABPA and 36 control patients [114]. The definition of the diagnostic accuracy wasthe number of correctly positively categorised patients plus the correctly negatively categorisedpatients as a percentage of the total.

Radiology

Radiological imaging in most patients with ABPA shows centrally located, cylindrical bronchiectasis,while the presence of distal bronchiectasis is rare [115]. The radiological classification haspredominantly prognostic implications as it cannot distinguish between bronchiectasis caused by ABPA or another factor [116]. HRCT scanning is regarded as the gold standard to identify bronchiectasis as a morphological diagnosis and correlates with the functional lung capacity of patients [117, 118]. Chest radiography lacks the sensitivity needed to rule out bronchiectasis and,therefore, HRCT is required if no abnormalities appear and ABPA is suspected. In ABPA, HRCT canbe used to monitor disease progression and is directive for the therapeutic strategy.

Treatment

The treatment of ABPA depends upon two important factors: 1) glucocorticoids to dampen theimmunological activity, and 2) antifungal agents to suppress the antigenic load.

Although glucocorticoids are the mainstay in ABPA treatment, no well-designed studies have beencarried out. Neither the optimal dose regimen nor the optimal duration of therapy has ever beendetermined [119]. In asthmatics the optimal dose and treatment scheme as regarded by expertopinion is prednisone 0.5–1.0 mg?kg-1?day -1 for 2 weeks, followed by an alternate day regimen,

which is tapered to zero during a 3–6-month period. In CF patients the prolonged use of glucocorticoids may induce severe side-effects such as glucose intolerance, growth suppression,cataracts and osteoporosis [120–122]. Therefore, the use of monthly pulses with methylpredni-solone has been suggested as a treatment for ABPA in CF patients. Two small studies with 13 CFpatients showed clinical and laboratory improvement after 0.3–1 mg?kg-1?day -1 and 10–15 mg?kg-1?day -1, respectively [123, 124]. Figure 4 illustrates the effect of systemic steroids in aCF patient with ABPA.

Inhaled glucocorticoids

Recently it was reported that inhaled glucocorticoids are significantly linked with the prevalence of Aspergillus in lungs of CF patients [125], which might increase their risk of suffering from ABPA. Theefficacy of inhaled steroids in patientswith ABPA has never been docu-mented and hence this treatment isnot recommended in patients withCF. Some small case series in patientswith asthma and ABPA indicatesome beneficial effects of inhaledglucocorticoids [126, 127]. How-

ever, the single largest study withinhaled beclomethasone shows nobeneficial effect at all [128]. There-fore, the use of inhaled glucocorti-coids seems limited in CF patientsand implicates limited value forpatients with asthma.

a) b)

Figure 4. Chest radiograph of a 12-year-old cystic fibrosis patient

with allergic bronchopulmonary aspergillosis a) before and b) after a6-week course of systemic steroids.

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Antifungal agents

It has been suggested that itraconazole modifies the immunological activation associated withABPA and can improve clinical outcome, at least over a 16-week period. The largest multicentrerandomised controlled trial found significantly lower need for steroids decreased serum IgEconcentrations and improved clinical findings in patients using itraconazole when compared withthose who did not [129].

The most recent Cochrane review (updated in 2010) on the efficacy of itraconazole in thetreatment of patients with CF concluded that evidence is limited and that further research isrequired [13]. Itraconazole might be used as an adjuvant to glucocorticoid treatment, presumably lowering the required dosage and thereby the side-effects of systemic steroids. The dosage of itraconazole is generally accepted to be 200 mg twice a day with a start dosage of 200 mg threetimes a day for 3 days. Liver function tests should be monitored monthly to prevent toxicity. Apotential concern in patients using both inhaled corticosteroids and itraconazole is adrenalsuppression due to an increase in steroid levels in serum [130].

Immunomodulatory therapy

With the progressing knowledge in the immunological mechanisms involved in patients withABPA, the possibility of developing a more cause-related therapy becomes ever more apparent. Inexperimental settings some successes have been achieved. For example Asp f 1-derived peptide P1,prophylactically and therapeutically administrated to BALB/c mice is effective in regulating anallergic response to allergens/antigens of A. fumigatus [131]. The first results obtained by theadministration of allergen-derived peptides to shift an Aspergillus specific Th2 response to aprotective Th1 are promising.

An example of immunomodulative therapy in a clinical setting is the introduction of omalizumabin children with CF and ABPA. Omalizumab is a humanised monoclonal antibody against IgE.Currently, as documented in case reports, a total of seven children who were described asirresponsive to glucocorticoid treatment were found to have improved lung function after using300–375 mg omalizumab subcutaneously every 2 weeks [132–135]. However, in order to introduceomalizumab in daily clinical routine, more clinical trials are warranted.

Conclusion

The aim of this chapter was to provide an overview of the clinical features of ABPA, the diagnostic

criteria and the underlying pathophysiological immune mechanisms. ABPA consists of an A. fumigatus -driven hypersensitivity reaction in predominantly asthmatic and CF patients.Polymorphisms in genes that drive innate and adaptive immune mechanisms, as well as loss-of-function mutations in CFTR, are associated with the development of a strong Th2 response andABPA. Continuous inhalation of A. fumigatus and resulting chronic infections, in combinationwith genetic predisposition, fuel a chronic inflammatory hypersensitivity response that eventually results in airway remodelling and functional impairment of the lung. The diagnostic process ischaracterised by a combination of tests evaluating lung function, serum hypersensitivity parameters(aspecific and specific for A. fumigatus ), and radiological characteristics such as bronchiectasis.Treatment consists of dampening the immune response by the use of glucocorticoids and

suppressing the fungal burden by antifungal agents.

Recent insights into the pathogenesis, diagnostic measures and treatment possibilities illustrate theongoing effort aimed at preventing ABPA from causing invalidating lung disease. Promisingexamples are the establishment of CFTR mutations in ABPA pathogenesis, the superior testcharacteristics of TARC regarding the diagnosis of ABPA in CF patients, and the beneficial role of itraconazole to glucocorticoids in treatment.

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None declared.

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Chapter 8

Nontuberculous

mycobacterial

infectionsC.L. Daley

Summary Nontuberculous mycobacteria (NTM) represent a large groupof bacteria that have been isolated from environmental sources.When NTM are inhaled by a susceptible individual, infectioncan occur and lead to progressive lung disease. Epidemiologicalstudies have described increases in the prevalence of NTMdisease in multiple areas worldwide. Risk factors for diseaseinclude chronic lung diseases, such as bronchiectasis and

chronic obstructive pulmonary disease, as well as various formsof immune deficiency. Patients typically present with eitherfibrocavitary or nodular bronchiectatic disease. Isolation of NTM from respiratory specimens does not always indicatedisease so clinicians must evaluate clinical, radiographic andmicrobiologic information in order to diagnosis NTM-relatedlung disease. The American Thoracic Society has developeddiagnostic criteria that can aid clinicians but the criteria cannotaccount for all clinical scenarios or for all NTM species giventhe large spectrum of pathogenicity encountered. Treatmentusually consists of at least two antibiotics but the exact regimen will vary depending on the species and there is some variation inrecommendations.

Keywords: Bronchiectasis, mycobacteria, Mycobacteriumavium complex, nontuberculous mycobacterial infections

Correspondence: C.L. Daley, Divisionof Mycobacterial and Respiratory Infections, National Jewish Health,1400 Jackson Street, Denver, CO80206, USA, [email protected]


N

ontuberculous mycobacteria (NTM) comprise ,140 species, many of which have been

reported to cause disease in humans. Based on their rate of growth in subculture, NTM havetraditionally been divided into slowly and rapidly growing species (table 1) [1–3]. Also referred toas environmental mycobacteria, NTM have been isolated from natural and drinking watersupplies, as well as soil [4–7]. The presumed source of infection is exposure to these environmentalreservoirs because human-to-human transmission has not been documented. When inhaled by susceptible individuals, such as those with chronic obstructive lung disease or bronchiectasis,infection with NTM can lead to a chronic, progressive and sometimes fatal lung disease.

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Despite their frequent isolation in the environment and human specimens, NTM were notwidely recognised as a cause of human disease until the late 1950s. Since that time, the numberof new species of NTM has grown dramatically [3] and the rate of disease related to NTM hasalso increased, overtaking the rate of tuberculosis (TB) in some areas [8]. Diagnosis andtreatment of NTM lung disease remains challenging for clinicians and depending on the extentof disease and species involved, a cure may be difficult to achieve. When considering treatment,clinicians must weight the potential benefits of therapy against the cost and potential side-effects of current regimens.

Epidemiology

Incidence and prevalence

The epidemiology of NTM disease has been difficult to determine because reporting is notmandatory in most countries and differentiation between infection and disease is often difficult.Although the incidence and prevalence of NTM infections have varied significantly across studies,recent studies have reported high rates of NTM pulmonary disease, particularly in olderpopulations [9–12]. Among 933 patients with at least 1 NTM isolate in Oregon (USA), 527 (56%)met the American Thoracic Society (ATS) microbiological definition for disease giving anannualised prevalence of 5.6 cases per 100,000 for pulmonary disease [9]. The prevalence wassignificantly higher in females (6.4 cases per 100,000) than males (4.7 cases per 100,000) and was

highest in persons aged .50 years (15.5 cases per 100,000). In another report from Oregon, theoverall 2-year prevalence of NTM pulmonary disease was 8.6 cases per 100,000 and increased to20.4 cases per 100,000 in those aged o50 years [10]. The annualised prevalence of NTM lungdisease within four integrated healthcare delivery systems in the USA ranged from 1.4 to 6.6 per100,000 [11]. Among persons aged o60 years, annual prevalence was 26.7 per 100,000.

Studies from Canada [8], Australia [12], Taiwan [13], the Netherlands [14] and the USA [11, 15]have reported increases in the incidence or prevalence of NTM. MARRAS et al. [8] reported anincrease in the number of pulmonary NTM isolates in Ontario (Canada) from 9.1 per 100,000 in1997 to 14.1 per 100,000 in 2003. Difficulty in eradicating NTM infections resulted in a prevalencehigher than that of tuberculosis [16]. More recently, two studies from the USA reported increasesin NTM pulmonary disease [11, 15]. In a study examining the prevalence of NTM lung disease infour integrated healthcare delivery systems, there was a 2.6% and 2.9% increase per year in femalesand males, respectively [11]. Pulmonary NTM hospitalisations increased significantly among bothmales and females between 1998 and 2005 in a study involving 11 states in the USA [15]. Annualprevalence increased among males and females in Florida (3.2% and 6.5%, respectively) andamong females in New York (4.6% per year) with no significant changes in California.

Table 1. Examples of slowly growing and rapidly growing nontuberculous mycobacteria that have been

reported to cause lung disease

Slowly growing mycobacteria Rapidly growing mycobacteria

Mycobacterium arupense Mycobacterium kubicae Mycobacterium abscessus Mycobacterium fortuitum

Mycobacterium asiaticum Mycobacterium lentiflavum Mycobacterium alvei Mycobacterium mageritense

Mycobacterium avium Mycobacterium malmoense Mycobacterium boenickei Mycobacterium massiliense

Mycobacterium branderi Mycobacterium palustre Mycobacterium bollettii Mycobacterium mucogenicum

Mycobacterium celatum Mycobacterium saskatchewanse Mycobacterium brumae Mycobacterium peregrinum Mycobacterium chimaera Mycobacterium scrofulaceum Mycobacterium chelonae Mycobacterium phocaicum

Mycobacterium flavescens Mycobacterium shimodei Mycobacterium confluentis Mycobacterium septicum

Mycobacterium florentinum Mycobacterium simiae Mycobacteium elephantis Mycobacterium smegmatis

Mycobacterium heckeshornense Mycobacterium szulgai Mycobacterium goodii Mycobaterium thermoresistible

Mycobacterium intermedium Mycobacterium triplex Mycobacterium holsaticum

Mycobacterium interjectum Mycobacterium terrae

Mycobacterium intracellulare Mycobacterium xenopi

Mycobacterium kansasii

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I N F E C

T I O N S



Earlier descriptions of pulmonary NTM disease described a male predilection for disease.However, in three recent studies from the USA, a higher proportion of disease was observed infemales than males [9–11]. Over an 8-year period from 1998 to 2005, the overall prevalence rate of hospitalisations for NTM pulmonary disease in the USA was highest in females aged o70 years(9.4 per 100,000) compared with similarly age matched males (7.6 per 100,000) [11].

The reasons for the increase in incidence and prevalence have not been explained although

increased awareness of the disease and improved diagnostic techniques could be factors. A trueincrease in incidence could be related to changes in the host such as an aging population, anincreased prevalence of chronic lung disease or an increase in the number of immunocompro-mised individuals. The observation of a decreased incidence of pulmonary TB and an increasedincidence of pulmonary NTM [8] could be explained by cross-immunity between mycobacterialspecies. Finally, an increase in the prevalence or virulence of organisms in the environment orchanges in human behaviour that would lead to increased exposure to organisms could becontributors. In support of the latter, the frequency of skin reactivity to purified proteinderivative-B, which used antigens from Mycobacterium intracellulare , increased from 11.2% in1971–1972 to 16.6% in 1999–2000 [17].

Risk factors for NTM infection and disease

Studies utilising delayed type hypersensitivity reaction to subcutaneously injected mycobacterialantigens have estimated that 11–33.5% of the population in the USA has been exposed to NTM[18–21]. A prospective study using skin testing data from Palm Beach, Florida reported that 32.9%of 447 participants in a population-based random household survey had a positive reaction toMycobacterium avium sensitin [21]. Predictors of a positive reaction included Black race, birthoutside the USA and .6 years cumulative exposure to soil. Using data from the National Health andNutrition Examination Survey (NHANES), investigators reported similar findings with regards tosensitisation to M. intracellulare [17]. Male sex, non-Hispanic Black race and birth outside the USAwere each independently associated with sensitisation. These two studies are interesting in that skintest reactivity to either M. avium or M. intracellulare antigens was associated with factors probably associated with soil exposure. However, at least in the USA, disease seems to be more common inolder Caucasian females. Thus, the risk factors for exposure and infection may be different fromthose associated with disease.

Historically male sex has been considered a risk factor for NTM lung disease and males continueto make up the majority of patients in some areas [14]. However, studies from the USA and SouthKorea have noted a female predominance. In Oregon, as noted previously, the rate of NTMpulmonary diseases was higher in females than males and females made up 60% of cases. Why the

shift to a female predominance remains unclear. However, there is likely a genetic link becausemany females who develop bronchiectasis and NTM infection share a similar body typecharacterised by tall slender status with a higher frequency of pectus excavatum, kyphoscoliosisand mitral valve prolapse than females who do not have NTM infection [22–24]. This conditionwas first described by PRINCE et al. [25] in 1989 and later referred to as the ‘‘Lady WindermereSyndrome’’ after the character in Oscar Wilde’s play Lady Windermere’s Fan, the referencereferring to fastidious behaviour in the character [26]. Recently, investigators reported that femalepatients with pulmonary NTM disease were taller, thinner and weighed less than matched controlsubjects [22]. To date, extensive evaluation of the immune system of these patients has beenunrevealing but mutations in the cystic fibrosis transmembrane conductance regulator gene are

common [22, 27].

Most NTM are significantly less pathogenic than Mycobacterium tuberculosis and probably requiresome degree of host impairment to result in disease. Impairment can be caused by immune defectsor chronic lung disease of which the latter appears to be most common. NTM disease has beendescribed in association with cystic fibrosis (CF), chronic obstructive pulmonary disease in-cluding a1-antitrypsin deficiency, cavitary lung disease, pneumoconiosis, bronchiectasis, prior TB,

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pulmonary alveolar proteinosis and chronic lung injury due to aspiration from gastro-oesophagealdisorders [28–34]. Bronchiectasis is an almost universal finding in females with NTM infectionand it is seen in many males with NTM infection. However, NTM infections have been reported tooccur in only 1–2% of bronchiectasis patients in two small series from the UK [35, 36]. Incontrast, studies have documented a high prevalence of NTM from sputum cultures in patientswith CF, with estimates ranging from 3% to 19.5% [37, 38].

Pulmonary disease due to NTM has been described in several other immunocompromised patientpopulations including transplant recipients [39–42], individuals taking tumour necrosis factor-ainhibitors [43–45], and patients with mutations in interferon (IFN)-c receptor 1, IFN-c receptor2, interleukin (IL)-12 p40 and the IL-12 receptor [46, 47]. Most of these patients present withdisseminated disease. Scientists have hypothesised that in slender, older females, decreased leptin,increased adiponectin and/or decreased oestrogens may account for the increased susceptibility toNTM infections [48]. Additionally, anomalies of fibrillin that lead to the expression of theimmunosuppressive cytokine transforming growth factor-b may further increase susceptibility toNTM lung disease [48].

Diagnosis and managementChronic pulmonary disease is the most common clinical presentation of NTM disease. In order todiagnose pulmonary NTM infection clinicians must weigh clinical, bacteriologic and radiographicinformation. Diagnostic criteria have been developed to aid the clinician in the diagnosticevaluation of persons suspected of having pulmonary NTM disease (table 2) [3, 49]. Although thediagnostic criteria provide a useful approach for the evaluation of patients with suspected NTMdisease, the approach has yet to be validated and it is impossible for a single set of diagnosticcriteria to be appropriate for all patients and species of NTM.

Unlike with TB, a single positive sputum culture for NTM is not diagnostic of pulmonary disease.

However, when two or more sputum cultures are positive the diagnosis of disease is more likely.For example, 98% of patients with two or more positive sputum cultures for M. avium complex (MAC) had evidence of progressive disease in a study from Japan [50]. Whether this microbiologiccriterion holds true for other NTM species is not known but given the wide range of pathogenicity among the various NTM species it is unlikely. Patients who are suspected of having NTM lungdisease but do not meet the diagnostic criteria should be followed clinically until the diagnosis iseither firmly established or excluded.

Laboratory diagnosis

Ultimately, the diagnosis of NTM disease is based on isolation of these organisms from clinicalspecimens. Both solid and broth media should be used for detection of mycobacteria and a semi-quantitative reporting of colony counts is recommended [3]. Most NTM grow within 2–3 weeks

Table 2. Microbiological criteria for diagnosis of nontuberculous mycobacteria lung disease

Respiratory specimen Culture and histopathological results

ATS recommendations BTS recommendations

Sputum specimen At least two separate positive cultures Positive cultures from specimens

obtained at least 7 days apart

Bronchial wash/lavage One positive culture Not described Tissue biopsy Compatible histopathology

(granulomatous inflammation) and a

positive biopsy culture and/or a positive

sputum or bronchial wash/lavage culture

Not described

ATS: American Thoracic Society; BTS: British Thoracic Society. Data from [3, 49].

1 1 8

N T M

I N F E C

T I O N S



on subculture and rapidly growing mycobacteria usually grow within 7 days of subculture.Identification of specific species can be based on phenotypic, chemotaxonomic and molecularmethods [3]. However, none of these procedures are sufficient to differentiate all NTM.

The clinical usefulness of drug susceptibility testing in the management of patients with NTMdisease remains controversial because in vitro results do not correlate well with clinical outcomesfor some mycobacterial species. Unfortunately, there is no single susceptibility method that is

recommended for all species of slowly growing mycobacteria. For MAC, a broth-based culturemethod with both microdilution and macrodilution methods are considered acceptable [3]. Initialisolates, as well as those from patients who fail or relapse, should be tested to clarithromycin.Isolates of Mycobacterium kansasii should be tested to rifampin as resistance to rifampin isassociated with treatment failure/relapse [3]. Broth microdilution minimum inhibitory con-centration (MIC) determination for susceptibility testing is recommended for rapidly growingmycobacteria.

As noted previously, skin test reactions to mycobacterial antigens are common in people living inendemic areas and, thus, are unable to distinguish NTM infection from disease. Tests that coulddistinguish infection from disease would be very helpful for clinicians. Measurement of anti-A60

immunoglobulin (Ig)G was reported to have a sensitivtity of 87% and specificity of 97% fordetection of Mycobacterium abscessus disease in patients with CF [51]. In Japan, KITADA et al. [52]evaluated the performance of an assay that detects serum IgA antibody to glycopeptidolipid coreantigen for the diagnosis of MAC lung disease. The sensitivity and specificity of the assay fordetecting MAC lung disease were 84% and 100%, respectively. Antibody levels were higher inpatients with nodular bronchiectatic disease compared with fibrocavitary disease and levelscorrelated with extent of disease by chest computed tomography (CT) scans. In a follow-up study of patients who underwent bronchoscopy, the sensitivity, specificity, positive predictive andnegative predictive values were 78.6%, 96.4%, 95.7% and 81.8%, respectively [53]. The sensitivity and specificity of the test for MAC pulmonary disease in patients with rheumatoid arthritis was

43% and 100%, respectively [54]. Although these serologic assays are not widely available, they may eventually find their way into diagnostic algorithms.

Slowly growing mycobacteria

The slowly growing mycobacteria include organisms with wide ranging pathogenicity such asM. kansasii and Mycobacterium szulgai , which are probably second only to M. tuberculosis in termsof disease producing capability and Mycobacterium gordonae and Mycobacterium terrae , whichrarely cause lung disease (table 1). MAC is typically the most common NTM to cause pulmonary disease but the frequency of M. avium versus M. intracellulare has varied between studies.

Recommendations for treatment vary between guidelines as highlighted in table 3 [3, 49, 55].

Mycobacterium avium complex

MAC includes the NTM species M. avium, of which there are several subspecies, M. intracellulare,and some that are as yet poorly described species. The traditionally recognised presentation of MAC lung disease has been as apical fibrocavitary lung disease similar to TB, usually in older maleswho have a history of cigarette smoking and alcohol abuse (fig. 1). MAC lung disease also presentswith nodular and interstitial nodular infiltrates frequently involving the right middle lobe orlingula, predominantly in post-menopausal, nonsmoking Caucasian females. This form of disease,

termed nodular/bronchiectatic disease, tends to have a much slower progression than cavitary disease. Nodular/bronchiectatic MAC lung disease is radiographically characterised by chest high-resolution CT (HRCT) findings that include multiple small centrilobular pulmonary nodules andbronchiectasis (fig. 2).

Treatment of MAC pulmonary disease involves a two to three drug regimen, which includesethambutol, a rifamycin (rifampicin or rifabutin) and a macrolide (clarithromycin or azithromycin).

1 1 9

C . L . D A L E Y



Unfortunately, treatment outcomes havevaried significantly between studies [3, 56].In a randomised controlled clinical trialconducted by the British Thoracic Society (BTS) comparing clarithromcyin versus ciprofloxacin in combination with rifam-picin and ethambutol for treatment of

pulmonary MAC, the clarithromycin-con-taining arm was associated with a higherall-cause mortality (48% versus 30%) butlower rates of failure and relapse (13% versus 23%) compared with the ciprofloxacin-containing arm [55]. In a previous BTSstudy, rifampicin and ethambutol were asso-ciated with a failure and relapse rate of 41%compared to 16% in the comparator arm,which contained isoniazid. Because the

macrolides are the only antimicrobial agentsfor which there is a correlation between in vitro susceptibility and clinical response andthe high rate of poor outcomes reportedwith rifampicin and ethambutol, the ATSrecommends inclusion of a macrolide inall patients. [57–62]. Therapy three times aweek is recommended for patients with non-cavitary disease [3]: this recommendation isbased on a study that demonstrated poor

bacteriological responses in patients whowere treated three times a week and hadevidence of cavitary disease [63]. Inter-mittent therapy with ethambutol may be associated with a lower rate of opticneuritis [64].

In patients with extensive radiographicdisease, cavitary disease, marolide resistancedisease or treatment failure, an injectable

aminoglycoside (amikacin or streptomycin)should be considered. A randomised trialfrom Japan reported that patients whoreceived streptomycin three times a week for the initial 3 months of therapy alongwith three other drugs had a faster sputumconversion rate compared with those thatwere in the placebo arm [65]. However,long-term relapse rates were not differentbetween arms.

Macrolide-resistant MAC lung disease isassociated with a poor prognosis [66]. Thetwo major risk factors for macrolide-resistant MAC disease are macrolide mono-therapy or treatment with macrolide andinadequate companion medications. The

T a b l e 3 .

R e c o m

m e n d a t i o n s f o r t h e t r e a t m e n t o f s e l e c t s l o w l y g r o w i n g n o n t u b e r c u

l o u s m y c o b a c t e r i a

O r g a n i s m

A T S r e c o m m e n d

a t i o n s

B T S

r e c o m m e n d a t i o n s

C o m m e n t s

D r u g s

D u r a t i o n

m o n t h s

#

D r u

g s

D u r a t i o n

m o n t h s

M A C

R i f a m p i c i n

E t h a m b u t o l

M a c r o l i d e

1 2 +

R i f a m

p i c i n

E t h a m

b u t o l

2 4

A T S : t h r e e t i m e s w e e k l y t h e r a p y i s r e c o m

m e n d e d f o r t h o s e w i t h

n o n - c

a v i t a r y d i s e a s e

. I n c a v i t a r y d i s e a s e

, a n a m i n o g l y c o s i d e

i s r e c o m m e n d e d f o r t h e f i r s t 2 m o

n t h s o f t h e r a p y

.

M y c o b a c t e r i u m

k a n s a s i i

R i f a m p i c i n

E t h a m b u t o l

I s o n i a z i d

1 2 +

R i f a m

p i c i n

E t h a m

b u t o l

9

B T S : i n p a t i e n t s w i t h c o m p r o m i s e d

i m m u n e d e f e n c e s

c o n t i n u e t r e a t m e n t f o r 1 5

– 2 4 m o n t h s

o r u n t i l t h e s p u t u m

h a s b e e n n e g a t i v e f o r 1 2 m o n t h s

.


m a l m o e n s e

R i f a m p i c i n

E t h a m b u t o l I s o n i a z i d ¡

f l u o r o q u i n o l o n e o r m a c r o l i d e

1 2 +

R i f a m

p i c i n

E t h a m

b u t o l

2 4

A T S : s p e c i f i c c o m b i n a t i o n s o f t h e s e d r u

g s a r e n o t d e s c r i b e d

.


x e n o p i

R i f a m p i c i n

E t h a m b u t o l

M a c r o l i d e I s o n i a z i d ¡ a m i n o g l y c o s i d e

1 2 +

R i f a m

p i c i n

E t h a m b u t o l ¡

m a c r o l i d e

2 4

A T S : a f l u o r o q u i n o l o n e c o u l d b e s u b s t i t u t e d

.

B T S

: a d d i t i o n o f c l a r i t h r o m y c i n m a y b e b e s t i n t e r m s o f

e f f i c a c y b u t w o u l d b e l i k e l y t o i n c r e a s e

r i s k o f s i d e - e

f f e c t s

.

A T S : A m e r i c a n T h

o r a c i c S o c i e t y ; B T S : B r i t i s h T h o r a c i c S o c i e t y ; M A C : M y c o b a c t e r i u m a v i u m c o m p l e x

. # : t r e a t m e n t s h

o u l d c o n t i n u e f o r 1 2 m o n t h s b e y

o n d t h e d a t e o f c u l t u r e

c o n v e r s i o n

. D a t a f r o m

[ 3 ,

4 9

, 5 5 ] .

1 2 0

N T M

I N F E C

T I O N S



treatment strategy associated withthe most success for macrolide-resistant MAC lung disease includesthe use of a multidrug regimenincluding a parenteral aminoglyco-side (streptomycin or amikacin) andsurgical resection (debulking) [66].

Clofazimine, in combination withethambutol and a macrolide, hasbeen used successfully to treat pul-monary MAC infections and, thus,may be a possible alternative drug formacrolide-resistant disease [67].

Mycobacterium kansasii

M. kansasii is one of the most co-

mmon causes of NTM lung diseasein the USA, as well as some parts of Europe and Asia. While most pa-tients with M. kansasii lung diseasehave upper lobe fibro-cavitary abnor-malities similar to TB (fig. 3), essen-tially any pattern of radiographicabnormality can occur, particularly in HIV-infected patients [68].

According to the ATS, the re-commended regimen for treatingM. kansasii pulmonary disease in-cludes daily rifampicin (600 mg?day -1), isoniazid (300 mg?day -1) andethfoambutol (15 mg?kg-1?day -1), alladministered for 12 months beyondthe date of culture conversion [3].However, the BTS recommends ri-fampicin and ethambutol therapy for

a total of 9 months [49]. Substitutionof clarithromycin for isoniazid hasbeen associated with good short-termtreatment results with daily [69] andintermittent therapy [70].

Patients whose M. kansasii isolateshave become resistant to rifampi-cin as a result of previous therapy have been treated successfully witha regimen that consists of high-dose daily isoniazid (900 mg), high-dose ethambutol (25 mg?kg-1

?day -1) and sulfamethoxazole (1.0 g three times per day) combinedwith several months of streptomycin or amikacin [71]. The excellent in vitro activity of clarithromycin and moxifloxacin against M. kansasii suggests that multidrug regimenscontaining these agents are likely to be even more effective for treatment of a patient withrifampicin-resistant M. kansasii disease.

a)

b)

Figure 1. A 59-year-old male smoker with cavitary Mycobacterium

avium complex lung disease. The patient, who presented withcough, fatigue and weight loss, was found to have acid-fast bacilli

on smear microscopy. Previous treatment with rifampicin and

clarithromcyin resulted in macrolide resistance. a) Chest radiographshowing cavitary consolidation in right upper lobe, volume loss,

pleural thickening and scattered nodular opacities. b) Computed

tomography slice showing large cavity in right upper lung withadjacent consolidation and bilateral severe emphysema.

1 2 1

C . L . D A L E Y



Mycobacterium malmoense

Mycobacterium malmoense is con-sidered the second most seriouspathogen after MAC in northernEurope, although the clinical rele-vance of M. malmoense isolates has

varied between studies. For exam-ple, in the Netherlands [72, 73],70–80% of isolates are reported tobe clinically relevant whereas inthe USA, M. malmoense is seldomconsidered clinically significant. Pa-tients with M. malmoense lungdisease frequently have pre-existingobstructive lung disease and presentwith radiograph findings similar to

other cavitary NTM lung diseasepathogens.

In a recent report, clarithromycin,rifampicin and ethambutol werecompared with a regimen consist-ing of ciprofloxacin, rifampicin andethambutol [55]. Overall, a morefavourable response to therapy wasreported with the macrolide-con-

taining regimen, although overall mortality was not different between the two regimens.Although the optimal management of M. malmoense has yet to be determined [55, 73, 74] a twoto four drug regimen is recommended that would include, at a minimum, ethambutol andrifampicin [73].

Mycobacterium xenopi

Mycobacterium xenopi is a com-mon cause of NTM lung disease inCanada, the UK, and some parts of Europe [75]. Radiographic find-

ings with M. xenopi pulmonary disease are variable but most ofteninclude upper lobe cavitary changescompatible with TB. M. xenopi isolates were reported to have fa-vourable in vitro MICs to isoniazid,rifampin and ethambutol in a study from the Netherlands [75]; how-ever, studies have failed to find acorrelation between in vitro drug

susceptibility results and treatmentoutcomes [76].

To date, the optimal treatmentregimen has not yet been deter-mined. In a multicentre, rando-mised trial comparing a regimen of

Figure 2. A 65-year-old nonsmoking female with history of cough,

fatigue and sinopulmonary infections for several years. Her sputum

was culture positive for Mycobacterium avium complex. Chestcomputed tomography slice showing right middle lobe and lingular

bronchiectasis with atelectasis and consolidation. Note the cen-

trilobular nodules in the dependent areas of the lower lobesbilaterally.

Figure 3. A 58-year-old female with Mycobacterium kansasii lung

disease. The patient presented with cough, fever and weight loss.She was treated as a tuberculosis suspect initially but her sputum

specimen grew M. kansasii . Chest computed tomography slice

demonstrating a large right upper lobe cavity.

1 2 2

N T M

I N F E C

T I O N S



clarithromycin, rifampin and ethambutol with ciprofloxacin, rifampin and ethambutol [55],there was no difference in the treatment success, failure or relapse rates between groups.All-cause mortality was relatively high and somewhat higher in the ciprofloxacin arm, butdeath directly related to M. xenopi was low. Even with variable treatment regimens,antimicrobial treatment cured 58% of patients who met ATS criteria for M. xenopi lung diseasein a retrospective study from the Netherlands [75]. Currently, the BTS recommendsethambutol and rifampicin for 24 months of therapy whereas the ATS recommends the

addition of a macrolide and isoniazid and possibly an aminoglycoside depending on theseverity of disease.

Rapidly growing mycobacteria

Because many rapidly growing mycobacteria are not pathogenic in humans it is important toidentify organisms within this group to the species level since this could affect both treatment andprognosis (table 1).

Mycobacterium abscessus complex M. abscessus is one of the most common NTM infections in the USA and accounts for 65–80% of lung infections due to rapidly growing mycobacteria [29, 77]. Recent studies have demonstratedthat M. abscessus consists of three species, M. abscessus (sensu stricto ) Mycobacterium massiliense and Mycobacterium bolettii [78, 79]. In the USA, most patients with pulmonary disease due toM. abscessus complex are nonsmoking, Caucasian females with a median age of ,60 years[29, 80]. Similarly, in South Korea the median age of patients with pulmonary disease is 55 yearsand almost all of the patients are nonsmoking females [81]. However, in the Netherlands, over half of the patients are male many of whom have predisposing lung disease [82].

The chest radiograph usually shows multi-lobar, reticulonodular or mixed reticulonodular-alveolaropacities [29]. HRCT findings include the presence of cylindrical bronchiectasis with multiple smallnodules, similar to MAC lung disease (fig. 4) [29, 83, 84]. Cavitation has been reported in 10–44% of patients [29, 80, 81].

Unfortunately , M. abscessus hasdemonstrated in vitro activity toonly a few antimicrobial agents.The ATS recommends therapy with 2–4 months of intravenousantibiotics such as imipenem orcefoxitin plus amikacin given daily or three times per week [3]. Oralagents that have demonstrated in vitro activity should be included inthe treatment regimen. Unfortu-nately, macrolides are the only oralagents typically active in vitro against M. abscessus . Studies havedemonstrated the presence of anerythromycin ribosomal methylasegene, erm(41), in M. abscessus ,which could result in the develop-ment of macrolide resistance andpossibly affect treatment responses[77, 85]. Other drugs that some-times demonstrate in vitro activity

Figure 4. A 70-year-old nonsmoking female with several year historyof cough, fatigue and weight loss. The patient had a history of severe

gastro-oesophageal reflux and recurrent pneumonias. Her sputum

cultures were consistently positive for Mycobacterium abscessus .Chest computed tomography slice showing diffuse bronchiectasis

with scattered centrilobular and subcentimeter nodules. There is an

area of airspace of opacity in the posterior left lower lobe.

1 2 3

C . L . D A L E Y



include linezolid and tigecycline, however, both drugs are associated with frequent adverse effects[86, 87].

Because of the high levels of in vitro resistance, cure is difficult to achieve in patients with lungdisease due to M. abscessus . In South Korea, JEON et al. [81] reported the outcomes of 65 patientswith pulmonary disease who were treated with a standardised regimen. Patients were hospitalisedand treated with intravenous cefoxitin and twice daily amikacin plus oral clarithromycin,

ciprofloxacin and doxycycline. After 1 month the intravenous drugs were stopped and the oralmedications continued for a total of 24 months and at least12 months beyond the date of cultureconversion [81]. 83% of the patients reported improvement in symptoms and 74% hadradiographic improvement as documented by HRCT. Sputum conversion and maintenance of negative sputum cultures for .12 months was achieved in 38 (53%) patients. However, drug-related adverse events were common. Neutropenia and thrombocytopenia associated withcefoxitin developed in 33 (51%) and four (6%) patients, respectively. Drug-induced hepatoxicity occurred in 10 (15%) patients. Cefoxitin had to be stopped, and in some cases switched toimipenem, in the majority of patients.

In a recent report from Denver, CO, USA, the outcomes of 107 patients treated for pulmonary

M. abscessus disease were reported [80]. Treatment regimens varied but followed current ATSrecommendations. Cough, sputum production and fatigue remained stable, improved or resolvedin 80%, 69% and 59% of patients, respectively. Treatment outcomes were disappointing: 20 (29%)out of 69 patients remained culture positive, 16 (23%) patients converted but relapsed, 33 (48%)patients converted to negative and did not relapse and 17 patients (16%) died during the study period.

As noted previously, speciation of the rapidly growing mycobacteria may be important becauseoutcomes may vary based on the species of NTM. KOH et al. [77] reported significant differencesin the clinical, radiographic and microbiologic outcomes in patients treated for M. abscessus versus

M. massiliense . Sputum conversion and maintenance of negative cultures occurred in 88% of patients with M. massiliense compared with 25% of patients with M. abscessus , despite receiving asimilar treatment regimen. When isolates of M. abscessus were incubated with clarithromycin, allbecame resistant within 7 days and the MIC continued to increase at day 14. In contrast, none of the M. massiliense isolates acquired resistance upon exposure to clarithromycin. The erm(41) genewas present in all of the M. abscessus isolates but was partially deleted in the M. massiliense isolates.

A combination of surgical resection and chemotherapy may increase the chance of cure in patientswho have focal lung disease and who can tolerate resection. Among 14 (22%) patients withpulmonary M. abscessus infection in South Korea who underwent surgical resection, negativesputum culture conversion was achieved within a median of 1.5 months and was maintained in

88% of those with pre-operative culture-positive sputum. Similarly, in a study from the USA,patients who had surgical resection plus medical therapy were more likely to convert their culturesto negative and not relapse compared with medical therapy alone (65% versus 39%; p50.041)[80]. Moreover, significantly more patients who underwent surgery converted sputum cultures tonegative and remained negative for at least 1 year when compared with those who receivedmedical therapy alone (57% versus 28%; p50.022).

Mycobacterium chelonae and Mycobacterium fortuitum

Although Mycobacterium chelonae and Mycobacterium fortuitum are less likely to cause lung

disease than M. abscessus the clinical and radiographic presentations are similar [29, 88]. Of 26patients in South Korea who grew M. fortuitum from two or more sputum specimens, 25 were nottreated and none showed evidence of progressive disease over a median of 12.5 months of follow-up [88].

Isolates of M. chelonae are usually susceptible to the macrolides, linezolid, tobramycin andimipenem and uniformly resistant to cefoxitin [89–91]. Other active drugs may include amikacin,

1 2 4

N T M

I N F E C

T I O N S



clofazimine, doxycycline and fluoroquinolones. The ATS recommends that treatment of M. chelonae infections should consist of at least two drugs to which in vitro drug susceptibility has been demonstrated. Unlike M. abscessus and M. fortuitum, M. chelonae does not appear topossess a copy of erm(41) [85].

In contrast to M. abscessus and M. chelonae , M. fortuitum demonstrates broader in vitro su-sceptibility to both oral and intravenous antimicrobial drugs including the newer macrolides,

fluoroquinolones, tetracycline derivatives, sulfonamides and intravenous drugs imipenem andcefoxitin [3]. Although most isolates of M. fortuitum are susceptible in vitro to the macrolides, they should be used with caution because of the presence of erm(41) [92]. As with M. chelonae ,M. fortuitum lung disease should be treated with at least two drugs to which in vitro susceptibility has been demonstrated [3].

Surgical therapy for NTM lung disease

Patients who have failed a standard therapeutic regimen, particularly those who harbour resistantorganisms, may benefit from surgical resection of the most affected areas. In 12 published series

involving a total of 602 patients (range 8–236), the post-operative sputum culture conversion rateranged from 82% to 100% with a mean conversion rate of 94% [93]. Long-term relapse was notreported in all studies but ranged from 0% to 13%.

The benefits must be weighed against the possible complications of surgery. In seven surgicalseries reported during the macrolide era, the rate of complications varied from 0% to 44%averaging approximately 25% [94–100]. In the largest study to date in Colorado (USA),MITCHELL et al. [99] reported the outcomes of 236 patients who underwent lung resection forNTM pulmonary disease over a 23-year period. Minor complications were reported in 18.5% of the patients with 31 (11.7%) suffering from serious complications. Bronchopleural fistula

occurred in 11 (4.2%) cases. No operative mortality was reported in six case series and post-operative mortality ranged from 0% to 11%. In the study from Colorado, seven (2.6%) patientsdied as a result of the procedure; however, the mortality rate was only 0.6% for the last 162patients that were operated on from 2001 to 2006. Many of these latter patients underwentvideo-assisted thoracoscopic surgery. Because case volume may be associated with outcomes,surgery should be performed by thoracic surgeons with extensive experience in performing thistype of surgery [99].

Conclusion

NTM represent a broad array of organisms with varying prevalence and pathogenicity. Pulmonary infections due to NTM appear to be increasing and the epidemiology is shifting toward a femalepredominance in some areas. Clinicians must consider clinical, radiographic and bacteriologicinformation when diagnosing NTM pulmonary infection. Although diagnostic criteria exist, thesehave yet to be prospectively validated. Consideration of the species of NTM is an increasingly important element of diagnosis and may impact the outcomes of therapy. Treatment regimensvary by NTM species as do treatment outcomes. Future areas of research should focus on theepidemiology of NTM infections, transmission of infection, risks for disease progression,development of new diagnostics and ultimately development of new drugs and treatmentregimens. Until we have a better understanding of the transmission and pathogenesis of these

difficult to treat infections, it will be difficult to formulate a rationale plan for prevention of infection.


None declared.

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56. Field SK, Fisher D, Cowie RL. Mycobacterium avium complex pulmonary disease in patients without HIV

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58. Griffith DE, Brown BA, Girard WM, et al. Azithromycin activity against Mycobacterium avium complex lungdisease in patients who were not infected with human immunodeficiency virus. Clin Infect Dis 1996; 23: 983–989.

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60. Dautzenberg BD, Piperno P, Diot C, et al. Clarithromycin in the treatment of Mycobacterium avium lung

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61. Wallace RJ Jr, Brown BA, Griffith DE, et al. Clarithromycin regimens for pulmonary Mycobacterium avium

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62. Kobashi Y, Yoshida K, Miyashita N, et al. Relationship between clinical efficacy of treatment of pulmonary

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63. Lam PK, Griffith DE, Aksamit TR, et al. Factors related to response to intermittent treatment of Mycobacterium

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65. Kobashi Y, Matsushima T, Oka M. A double-blind randomized study of aminoglycoside infusion with combined

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66. Griffith DE, Brown-Elliott BA, Langsjoen B, et al. Clinical and molecular analysis of macrolide resistance in


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72. Hoefsloot W, van Ingen J, de Lange WC, et al. Clinical relevance of Mycobacterium malmoense isolation in the

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79. Adekambi T, Berger P, Raoult D, et al. rpoB gene sequence-based characterization of emerging non-tuberculous

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80. Jarand J, Levin A, Zhang L, et al. Clinical and microbiologic outcomes in patients receiving treatment for

Mycobacterium abscessus pulmonary disease. Clin Infect Dis 2011; 52: 565–571.

81. Jeon K, Kwon OJ, Lee NY, et al. Antibiotic treatment of Mycobacterium abscessus lung disease: a retrospective

analysis of 65 patients. Am J Respir Crit Care Med 2009; 180: 896–902.

82. van Ingen J, de Zwaan R, Dekhuijzen RP, et al. Clinical relevance of Mycobacterium chelonae -abscessus groupisolation in 95 patients. J Infect 2009; 59: 324–331.

83. Kim JS, Tanaka N, Newell JD, et al. Nontuberculous mycobacterial infection: CT scan findings, genotype, and

treatment responsiveness. Chest 2005; 128: 3863–3869.

84. Han D, Lee KS, Koh WJ, et al. Radiographic and CT findings of nontuberculous mycobacterial pulmonary

infection caused by Mycobacterium abscessus . AJR Am J Roentgenol 2003; 181: 513–517.

85. Nash KA, Brown-Elliott BA, Wallace RJ Jr. A novel gene, erm(41), confers inducible macrolide resistance to

clinical isolates of Mycobacterium abscessus but is absent from Mycobacterium chelonae . Antimicrob Agents

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86. Wallace RJ Jr, Brown-Elliott BA, Ward SC, et al. Activities of linezolid against rapidly growing mycobacteria.

Antimicrob Agents Chemother 2001; 45: 764–767.

87. Ntziora F, Falagas ME. Linezolid for the treatment of patients with [corrected] mycobacterial infections

[corrected] a systematic review. Int J Tuberc Lung Dis 2007; 11: 606–611.88. Park S, Suh GY, Chung MP, et al. Clinical significance of Mycobacterium fortuitum isolated from respiratory

specimens. Respir Med 2008; 102: 437–442.

89. Wallace RJ Jr, Brown BA, Onyi GO. Skin, soft tissue, and bone infections due to Mycobacterium chelonae :

importance of prior corticosteroid therapy, frequency of disseminated infections, and resistance to oral

antimicrobials other than clarithromycin. J Infect Dis 1982; 166: 405–412.

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90. Brown BA, Wallace RJ Jr, Onyi GO, et al. Activities of four macrolides, including clarithromycin, against

Mycobacterium fortuitum, Mycobacterium chelonae , and Mycobacterium chelonae-like organisms. Antimicrob


91. Swenson JM, Wallace RJ Jr, Silcox VA, et al. Antimicrobial susceptibility testing of 5 subgroups of Mycobacterium

fortuitum and Mycobacterium chelonae . Antimicrob Agents Chemother 1985; 28: 807–811.

92. Nash KA. Intrinsic macrolide resistance in Mycobacterium smegmatis is conferred by a novel erm gene, erm (38).

Antimicrob Agents Chemother 2003; 47: 3053–3060.

93. van Ingen J, Verhagen AF, Dekhuijzen PN, et al. Surgical treatment of non-tuberculous mycobacterial lung

disease: strike in time. Int J Tuberc Lung Dis 2010; 14: 99–105.

94. Nelson KG, Griffith DE, Brown BA, et al. Results of operation in Mycobacterium avium-intracellulare lung

disease. Ann Thorac Surg 1998; 66: 325–330.

95. Shiraishi Y, Fukushima K, Komatsu H, et al. Early pulmonary resection for localized Mycobacterium avium

complex disease. Ann Thorac Surg 1998; 66: 183–186.

96. Shiraishi Y, Nakajima Y, Takasuna K, et al. Surgery for Mycobacterium avium complex lung disease in the

clarithromycin era. Eur J Cardiothoracic Surg 2002; 21: 314–318.

97. Lang-Lazdunski L, Offredo C, Le Pimpec-Barthes F, et al. Pulmonary resection for Mycobacterium xenopi

pulmonary infection. Ann Thoracic Surg 2001; 72: 1877–1882.

98. Watanabe M, Hasegawa N, Ishizaka A, et al. Early pulmonary resection for Mycobacterium avium complex lung

disease treated with macrolides and quinolones. Ann Thoracic Surg 2006; 81: 2026–2030.

99. Mitchell JD, Bishop A, Cafaro A, et al. Anatomic lung resection for nontuberculous mycobacterial disease. Ann

Thoracic Surg 2008; 85: 1887–1892.

100. Koh WJ, Kim YH, Kwon OJ, et al. Surgical treatment of pulmonary diseases due to nontuberculous

mycobacteria. J Korean Med Sci 2008; 23: 397–401.

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Chapter 9

Ciliary dyskinesias:

primary ciliary

dyskinesia in adultsL.J. Lobo*, M.A. Zariwala # and P.G. Noone*

Summary Primary ciliary dyskinesia (PCD) is a genetic disorder of ciliastructure and function, chronic infections of the respiratory tract, fertility problems and disorders of organ laterality.Establishing a definitive diagnosis can be challenging, requiring a compatible phenotype and detection of ciliary functional andultra-structural defects, along with newer screening tools suchas nasal nitric oxide and genetics testing. 10 known PCD-

causing mutations within two genes are now available in aclinical panel, and in the future, comprehensive genetic testing may serve to identify young infants with PCD to improve thelong-term outlook for patients with the disease. Therapy includes regular pulmonary function testing and monitoring of sputum flora to allow a targeted approach to treatment.Referral to an academic centre with expertise in bronchiectasisand/or PCD is prudent to ensure access to the most recentdiagnostic testing and therapies. With increased understanding of the disease it is likely that we will expand the definitions of classic and non-classic PCD, as well as its relationship to lesscommon ciliopathies.

Keywords: Bronchiectasis, cilia, dynein, mucociliary clearance,nitric oxide, primary ciliary dyskinesia

*Division of Pulmonary Diseases, and#Dept of Pathology and Laboratory Medicine, University of NorthCarolina, Chapel Hill, NC, USA.

Correspondence: P.G. Noone, CB7020, Pulmonary Division, University of North Carolina School of Medicine, Chapel Hill NC 27599-7020, USA, [email protected]


C iliary dyskinesia refers to a syndrome of oto-sino-pulmonary disease with otheraccompanying phenotypic features. It is often referred to as primary ciliary dyskinesia

(PCD) and sometimes referred to as immotile cilia syndrome (ICS) or Kartagener syndrome, oroccasionally the motile ciliopathies [1–3]. PCD is currently the preferred term [4]. Althoughsecondary ciliary dyskinesia may be seen in diseases associated with acute and chronic airway inflammation and infection, this chapter will focus primarily on the genetically transmitted formof the disease, that is PCD, rather than nongenetic, generally secondary forms of the syndrome [5].Since the hallmarks of the disease are chronic lung disease with bronchiectasis, a brief discussion of the major respiratory features (bronchiectasis) is included, as well as a brief review of airway host

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defence. This will allow a better understanding of the role of cilia in health and disease. Thischapter will focus on disease in adults, as an excellent review of PCD in children was recently published [6].

PCD is a rare, usually autosomal recessive disease characterised by oto-sino-pulmonary disease,including bronchiectasis, organ laterality defects and male infertility. First described early in the 20thcentury, its disease origins as a defect in ciliary structure and function were described in Sweden in

the 1970s [7, 8]. The last decade or so has seen resurgence in interest in PCD, specifically a new focushas emerged from several groups worldwide on more precisely defining the major aspects of thedisease phenotype, including elucidating the molecular basis for the ciliary abnormalities. Such datawill help clinicians establish a diagnosis of PCD (which can be difficult in many circumstances),which in turn, will hopefully allow more targeted therapeutic approaches. Cystic fibrosis (CF) haslong been recognised as a prototype genetic disease associated with severe pulmonary disease andbronchiectasis, with intense research activity devoted to CF pathogenesis and treatment over the lastseveral decades. PCD offers a similar disease model to CF, albeit with a different basic aetiology,offering complementary insights into significant human disease associated with dysregulation of themucociliary clearance (MCC) apparatus in the respiratory tract.

The major clinical characteristics of PCD are chronic ear, sinus and lower airways symptoms andsigns from birth because of the failure of one of the major airway defence mechanisms, that of MCC. By adulthood, bronchiectasis is invariable and is characterised by an abnormal andpermanent dilation of bronchi. It is the consequence of inflammation and destruction of thestructural components of the bronchial walls, usually in the walls of the medium-sized airways,often at the level of segmental and sub-segmental bronchi. Most experts accept that a ‘‘viciouscycle’’ of infection and inflammation is created by the basic defect in airway host defence. Thisgenerates airway damage and further impairment of airway clearance, eventually with chroniccolonisation/infection with a variety of microorganisms, leading to further infection andinflammation and eventually destruction of conducting airways and even alveolar surfaces. In its

most severe form, bronchiectasis may lead to respiratory failure and death. For the clinician facedwith a patient with bronchiectasis, the diagnostic algorithm involves sifting through the variouscauses of the disease, with a predominant cause often elusive; thus, it may be labelled either asidiopathic or, with an appropriate history, as post-infectious bronchiectasis [9]. However, acareful clinical history, together with focused tests, may find an underlying cause such as CF orPCD, which is almost always helpful from genetic, prognostic, therapeutic and healthcare systemstandpoints.

Thus, structural and functional abnormalities of motile cilia and human flagellated cells (sperm)explain the complex PCD phenotype involving various organ systems. The motile cilia in the

respiratory tract are vital components of the mucociliary apparatus used in airway clearance andthe flagellated structures are important in the male and female reproductive systems. Left–rightasymmetric organ defects may also be part of the phenotype, for example, situs inversus totalis ,commonly known as Kartagener syndrome [10].

Normal cilia structure and function

In addition to humoral, cellular and innate immune systems, the respiratory tract has developedcomplex local physical defences to protect the airways from the myriad of inhaled pathogens,allergens and other inhaled noxious particles. One such mechanism is the mucociliary escalator,

which mechanically eliminates bacteria and particulates that deposit on the epithelial surface of therespiratory tract.

Cilia are hair-like attachments found on the epithelial surfaces (,200 per cell) of various organsand are anchored on by a basal body to the apical cytoplasm and extend from the cell surface intothe extracellular space. Each cilium is composed of approximately 250 proteins organised intolongitudinal microtubules, which make up the basic axonemal structure [11]. Based on the

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arrangement of the microtubules,cilia are classified into motile cilia,primary cilia and nodal cilia [12].Motile cilia are the cilia found inthe apical surfaces of the upper andlower respiratory tract, the epen-dymal cells lining the ventricles of

the central nervous system, theoviducts of the female reproductivetract and the flagellum of the malesperm. Motile cilia are organisedinto nine microtubule pair doub-lets, surrounding a central paircreating a distinctive 9+2 arrange-ment (fig. 1) [3]. The central pairis linked to the surrounding pairdoublet through an array of radial

spoke proteins and the surround-ing pair doublets are linked to one another via nexin linked proteins. Through ATP-containingdynein arms on the peripheral microtubules, the microtubules slide by one another to produceciliary motion [13]. The protein links between the microtubules limit the degree of sliding andallow the cilium to bend. Dyneins can be sub-divided into axonemal and cytoplasmic dyneins.Axonemal dyneins move cilia and flagella, as described previously, while cytoplasmic dyneins areinvolved in the organisation of spindle poles during mitosis [14]. Axonemal dyneins form twostructures, the inner and outer arms, and are attached to the microtubules of the nine outerdoublets throughout the length of the axoneme, thus they are central to the process of the bendingof the cilium or sperm tail. Through coordinated and synchronised bending, wave like movements

occur at ,16 Hz, which function to propel mucus and adherent particles/bacteria on the surfaceof the airway. Integral to the normal function of cilia is normal airway periciliary fluid layercomposition and function. One of the main pathogenetic mechanisms in CF is thought to bedysregulation of this fluid layer, which bathes cilia with a thin mucus layer on top [15]. It can bereadily seen, therefore, that two discrete abnormalities of MCC, one involving the cilia themselves,the other involving the fluid that bathes the cilia, may result in a broadly similar airway phenotype(bronchiectasis).

Finally, nodal cilia occur during embryonic development. In contrast to the 9+2 structure of motile cilia, they have a 9+0 configuration. They have a very interesting rotational movement,

resulting in leftward flow of extracellular fluid, which is important for cell signalling during thedevelopment of normal human left–right asymmetry (situs solitus ) [12]. Defects in the nodal ciliamay cause errors with left–right body orientation; for example, dextrocardia, situs inversus totalis and situs ambiguous [16–18]. This explains the association of organ laterality defects in PCD, aswell as other rare genetic diseases such as polycystic kidney disease, Senior–Loken syndrome,Alstrom syndrome, Bardet–Biedl syndrome and retinitis pigmentosa [19].

Clinical manifestations

The clinical signs and symptoms of PCD are shown in table 1.

The clinical phenotype that occurs with defective ciliary structure and function is fairly predictable. Cells lining the nasopharanx, middle ear, paranasal sinuses, the lower respiratory tractand the reproductive tract contain cilia and are generally affected in PCD when the disease is fully expressed. In contrast to CF, pancreatic function is preserved, and hepatobiliary disease is usually not a feature. In general, the clinical course of the disease is milder, with absence of the systemicproblems associated with CF such as nutritional issues and diabetes. Although there are few data

Outer dynein arm

Inner dynein arm

Microtubule A

Microtubule B

Radial spoke

Central complex

Figure 1. Diagram of a cross-section of the basic ciliary structure.

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on life expectancy in PCD, it is believed from clinical experience, and some cross-sectional and

longitudinal studies, that PCD carries a more favourable prognosis than CF [20, 21]. Nonetheless,the disease may be quite severe and some patients develop respiratory failure requiringconsideration for lung transplant [21].

As with CF, a clue to the diagnosis is a family history of PCD, particularly in populations with highlevels of consanguinity [22]. For example, there is a reported 1 in 2,200 prevalence of PCD in theAsian population of Britain [23]. The prevalence of PCD in the general population is unknown,although estimates based on mass radiology studies in differing countries (Scandinavia and Japan)suggest a range of ,1:16,000 to 1:40,000 depending on the techniques and calculations involved,and taking into account the likelihood that its prevalence is almost certainly underestimated, even

in these focused studies [6].

Oto-sino-pulmonary disease

At birth, newborns with PCD often present with a clinical syndrome of neonatal respiratory distress, indicating the importance of ciliary function in clearing the fetal lung [24, 25]. It is usefulto consider PCD with this clinical history, whether in later childhood or adulthood (althoughadult recall of neonatal events may not be reliable). Early childhood atelectasis, pneumonia,hypoxaemia or respiratory failure can be seen [4, 26]. Frequently, these problems may beattributed to other aetiologies (for example wet lung, aspiration or pneumonia), and PCD maybeoverlooked for some time. This is borne out by data showing the mean age at diagnosis in childrenwith PCD was .4 years even when persistent pulmonary symptoms occurred, such as chroniccough and persistent rhinitis [27]. Children with wheezing may also be labelled as having‘‘atypical’’ asthma that is unresponsive to appropriate therapy [28]. Frequently, infants and youngchildren have recurrent upper respiratory tract symptoms, including chronic rhinosinusitis andchronic otitis media [27]. Nasal polyps and conductive hearing loss from the recurrent infectionsand inflammation is common [29]. Most expert paediatricians discourage placement of drainage

Table 1. Clinical signs and symptoms of primary ciliary dyskinesia

By system affected By age of presentation

Middle ear Family history

Chronic otitis media with tube placement Communities or ethnicities with consanguinity

Conductive hearing loss Close (usually first degree) relatives with clinicalsymptomsNose and paranasal sinuses

AntenatalNeonatal rhinosinusitis

Heterotaxy on prenatal ultrasoundChronic nasal congestion and mucopurlent rhinitisNewborn periodChronic pansinusitis

Continuous rhinorrhoeaNasal polyposis

Respiratory distress or neonatal pneumoniaLung

ChildhoodNeonatal respiratory distressChronic productive coughChronic cough (lifelong)

Atypical asthma unresponsive to therapyRecurrent pneumonia

Idiopathic bronchiectasisBronchiectasisChronic rhinosinusitisGenitourinary tract

Recurrent otitis media with effusionMale and female fertility problem or history of

in vitro fertilisation Adolescence and adult life

Laterality defects Same as for childhood

Situs inversus totalis Subfertility and ectopic pregnancies in females

Heterotaxy (¡ congenital cardiovascularabnormalities)

Infertility in males with immotile sperm

Central nervous system

Sputum colonisation with smooth/mucoid

pseudomonas, other Gram-negative organisms,

or nontuberculous mycobacteriaHydrocephalus (rare)

Eye

Retinitis pigmentosa

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tubes (‘‘grommets’’), as these frequently lead to otorrhoea, worsening of the tympanic scarringand hearing loss over the long term [6, 25]. Although adult nutritional issues are generally not afeature of PCD, infants with PCD may have significant issues with severe gastro-oesophagealreflux, feeding and ability to obtain adequate nutrition and tend to be on the lower end of thegrowth curve [30]. In later childhood and early adulthood, the impaired MCC in the lowerrespiratory tract leads to recurrent episodes of bronchitis and pneumonias, which eventually leadsto bronchiectasis of the middle and lower lobes [31, 32]. In all age groups, chronic cough is a

predominant feature of the disease (often reported by family members), both in response to thechronic inflammation and as a compensatory mechanism for defective ciliary function and MCC[33]. Adults may develop clubbing as a marker of long standing pulmonary disease. By the timepatients present to adult clinics, many adults frequently have a history of lobectomy in early life,prior to the diagnosis being established. Since this procedure cannot usually correct what is, afterall, a general problem in the lung, it can rarely be recommended [21]. Typically the diseasemanifests itself as intermittent exacerbations of infectious symptoms, but always with a baselinelevel of chronic symptoms (as is usual for most patients with bronchiectasis, whatever the cause)[34]. At all stages of the disease the focus should be on minimising symptoms, improving quality of life and slowing declines in lung function (see later). Another unusual, but recently reported

complication of chronic airway diseases in older patients with PCD is that of lithoptysis, that is,expectoration of stone-like masses from the airways [35]. The hypothesis is that calcite stoneformation is a bio-mineralisation response to the chronic airway inflammation and retention of infected airway secretions in some patients with PCD.

Airway microbiology/imaging

It is not infrequent that adults present to bronchiectasis clinics having rarely had sputum cultures[21]. However, monitoring of the flora of the airway is important, since older adults often harbourproblematic organisms that may require specific treatment [21]. Based on monitoring protocols

developed for CF and small studies in PCD, it is recommend that airway cultures be performedevery 3 to 6 months [20, 21]. Initially, cultures of airway secretions (sputum cultures) grow Haemophilus influenzae, Streptococcus pneumoniae and Staphylococcus aureus . Once bronchiectasisis evident on chest imaging (high-resolution computed tomography (HRCT)), smooth andmucoid Pseudomonas aeruginosa and other opportunistic pathogens such as nontuberculousmycobacteria (NTM) may be present. In cross-sectional studies series, all adults .30 years of agehad evidence of bronchiectasis, with an increasing prevalence of these organisms [21, 36].

Pulmonary function testing

Most patients demonstrate progressive obstructive defects with advancing age. Although there arefew longitudinal data, cross-sectional studies suggest that the disease is milder than CF in terms of the progression of loss of lung function [21, 36]. Nonetheless, it is important in order to guidetreatment, to obtain baseline and serial measures of lung function and assess disease severity andprogression, as some patients will develop severe or end-stage lung disease [21]. Ongoing studies,involving larger numbers of patients in multiple centres, will better define longitudinal markersand the natural history of the disease.

Radiology

With more abundant and specialised imaging, bronchiectasis is being observed more frequently ingeneral. Thus, PCD may be considered in patients with HRCT-proven bronchiectasis. Thecomputed tomography scan characteristics of bronchiectatic airways are well described [37].However, HRCT features alone do not usually allow a confident distinction between cases of idiopathic versus post-infectious bronchiectasis versus known causes or associations of bronchiectasis, although there are certain patterns of disease distribution that support a diagnosisof PCD, for example, a predilection for the middle and lower lobes has been reported in patients

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with PCD, in contrast to the upper lobe distribution of cylindrical bronchiectasis in patients withCF [38]. Some authors suggest that absence of bronchiectasis on a HRCT scan may have a role inexcluding the diagnosis of PCD, at least in adults [31].

Reproductive tract abnormalities

Infertility in both males and females is also a prominent feature. 98–99% of males with PCD have

impaired spermatozoa motility secondary to defective sperm flagella [39]. Data are scattered infemales, but a consistent feature is that of normal or delayed fertility in some, while other femalesshow impaired fertility with an increased risk of ectopic pregnancy, presumably because of impaired ciliary function in the oviduct [40].

Organ laterality and other anatomic defects

During the embryonic period, thoraco-abdominal orientation is determined via the unidirec-tional, rotating beat of nodal cilia. With abnormal nodal ciliary structure and function, thoraco-abdominal organ orientation is random. This leads to situs inversus with reversal of the thoracicand abdominal organs in ,50% of patients with PCD [16, 21]. Occasionally, laterality defects arenot ‘‘pure’’, that is, situs ambiguous /heterotaxy may be present. This is the phenomenon of left–right asymmetry within specific organ systems, leading to either sole or randomly combinedanatomical deformities of the heart, liver and spleen. A recent series found that at least 6% of patients with PCD have heterotaxy, including complex congenital heart defects [17]. Defects in theouter dynein arm (ODA) may be a more common cilia abnormality in patients with laterality defects than that of the inner dynein arm (IDA) or central apparatus [17].

Rare associations of PCD

PCD is occasionally seen with rare diseases linked to abnormalities in primary cilia or sensory cilia,

for example in the kidney, retina and embryonic node, which may lead to a wide spectrum of clinical features. An example is PCD with retinitis pigmentosa. Mutations in the X-linked retinitispigmentosa GTPase regulator gene (RPGR) gene have been identified in a few cases of PCD co-segregating with retinitis pigmentosa [41, 42]. Ciliary dysfunction in both respiratory epitheliumand the photoreceptors of the retina seems to be the common factor [42]. Hydrocephalus may beseen in mice with PCD, but its association in humans is less clear, the problem may be secondary to the impaired cilia that line the ventricular ependymal cells of the central nervous system, whichhelps cerebrospinal fluid flow through the sylvian aqueduct [43–45].

Diagnostic approaches

Overview

Since the first reports of abnormal ciliary structure as the cause of PCD, the diagnosis of PCD hasusually been established by obtaining nasal samples of airway cilia for examination under light andelectron microscopy. With appropriate techniques, ciliary motion (absent or dyskinetic in PCD) may be defined and ciliary ultra-structure examined for abnormalities, the classic being absent or short/stubby dynein arms. However, these tests are quite dependent on technical factors and local expertise,and thus it can sometimes be a challenge to definitively diagnose PCD. Recently, however, thediagnostic work-up for PCD has evolved to encompass other methodologies, for example, measures

of nasal nitric oxide (NO), more sophisticated analyses of ciliary structure and function and genetictesting (see later). Often, the resources needed to make a definitive diagnosis are only available inspecialised centres. Nonetheless, a history yielding the symptomatic clues above should promptconsideration of the diagnosis and, if necessary, referral to the growing number of centres with aninterest and expertise in the diagnosis and treatment of PCD and related diseases. An algorithm of currently available tests is presented to help the clinician work through the process (fig. 2). It goeswithout saying that prior to consideration of the diagnosis of PCD, and embarking on a detailed

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work-up, other diseases can be considered and ruled out as appropriate [9]. As there are widevariations in PCD presentation and phenotype there may be overlap with CF, immunologicaldeficiencies, allergic bronchopulmonary aspergillosis (ABPA) and other causes of bronchiectasis.Other chapters in this Monograph address these diseases in considerable detail.

Clinical suspicion of PCD

CT chest scan with bronchiectasis(middle/lower lobe predominantlyand/or heterotaxy)

NoPCD unlikely#

Other aetiologies of bronchiectasisruled out

Yes

Yes

Yes

Yes

Yes

No

NoNasal NO level reduced (usually 5– 20% of normal) PCD unlikely#

Cilia examinationvia nasal biopsy

Ciliary beat frequency and pattern PCD not ruled out¶

Abnormal

Electron microscopy withultra-structural defect in cilia

Normal beat frequency, pattern andultra-structure makes PCD unlikely,but could be non-classic disease

PCD likely

Consider genetic testing for DNAI1 andDNAH5 using clinical panel at selectinstitutions (accounts for ~40%) and thereare select genetic tests and gene analysisavailable at specific academic centres

Normal

Normal

Rule out cystic fibrosis with a sweat chloridetest and/or CFTR gene mutation analysis

Rule out connective tissue disorders withRF, ANA and ANCA

Consider ABPA, asthma, allergic rhinitis, gastro-oesophageal reflux disease and α

1-antitrypsin

deficiency

Rule out primary immunodeficiencieswith Ig levels (IgG, IgA and IgM) and serumelectrophoresis and consider vaccine response

Figure 2. Diagnosis algorithm for primary ciliary dyskinesia (PCD) in adults. For clinical signs refer to table 1.

CT: computed tomography; NO: nitric oxide; CFTR: cystic fibrosis transmembrane conductance regulator;

Ig: immunoglobulin; RF: rheumatoid factor; ANA: antinuclear antibodies; ANCA: antineutrophil cytoplasmic

antibodies; ABPA: allergic bronchopulmonary aspergillosis. #: if clinical suspicion is still high for PCD other,more specific tests may be undertaken; ": normal ciliary beat frequency and pattern does not completely rule

out PCD.

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Screening tests versus diagnostic tests

Tests of ciliary function can be divided into those that are indirect and may be used to screenpatients (e.g. the nasal saccharin test) and those that definitively assess function and structure(ciliary beat frequency (CBF)/pattern tests and electron microscopy studies). Newer screening/diagnostic tests currently undergoing study include nasal NO, which may reflect ciliary structurefunction indirectly, immunofluorescent analysis of ciliary proteins, high-speed video-microscopy

to quantitate ciliary motion and clinically available panels of genetic tests known to be associatedwith ciliary structural abnormalities.

MCC: the saccharin test

The saccharin test is cheap and can be readily performed in the clinical setting as a screening test.However, it is subject to an array of technical factors that render it less reliable than othermethodologies. A 1–2 mm particle of saccharin is placed on the inferior nasal turbinate 1 cm fromthe anterior end (if too far anterior cilia actually beat forwards from the nose). The difficult part isthat the patient must sit quietly with the head bent forward without sniffing, sneezing, coughing,

eating or drinking. The time it takes for the patient to taste the saccharin is a rough measure of nasal MCC. Generally, tasting saccharin in ,30 minutes is normal. Patients with rhinosinusitiscommonly taste it within 60 minutes. If it is not tasted within 60 minutes, PCD can be considered.The test is not suitable for small children who will not sit still for 60 minutes, patients with a poorsense of taste and patients with a cold within the past 6 weeks [46].

NO levels

NO is present in high concentrations in the upper respiratory tract and is produced by theparanasal sinus epithelium [47]. NO is produced enzymatically from L-arginine by several

isoforms of NO synthase. NO appears to contribute to local host defence, modulate ciliary motility and serve as an aerocrine mediator in helping to maintain adequate ventilation–perfusionmatching in the lung [48]. Abnormal values of nasal NO have been reported in various sinus andlung diseases; for example, acute and chronic sinusitis, CF and nasal polyposis [48]. Quitefortuitously, low nasal NO levels were first reported in PCD in the early 1990s by a Scandinaviangroup researching exhaled NO in a variety of normal and diseased states [49]. The observation hasbeen replicated on several occasions and, although not fully understood at a mechanistic level, itseems to be a robust index of classic PCD [21, 50]. In individuals with PCD, levels of exhaled NOare extremely low (,10% of normal values) even when compared with patients with CF and othersinus disorders, where nasal NO may be low, although not usually in the PCD range [51, 52].

Interestingly, in one study, carriers (nonsmoking parents of patients with PCD) had intermediatelevels of nasal NO [21]. Confirmation of the diagnosis of PCD requires further diagnostic tests.Nevertheless, the highly reproducible nature of low nasal NO levels make it a valuable screeningtool [53].

Ciliary function

Transnasal brushings or nasal scrape samples may be obtained fairly readily via direct visualisationof the inferior turbinate, without local anaesthesia or sedation [54]. Ciliary beat patterns andfrequency can be seen under direct visualisation using a microscope, and classed as qualitatively

normal, dyskinetic or immotile [21, 55]. For more quantitative measures, CBF can be measuredand the ciliary waveform can be analysed using high-speed digital video imaging to differentiatebetween abnormal beating cilia and the normal beat patterns [56]. A cilium can be viewed in slow motion or frame by frame, with 40 to 50 frames per ciliary beat cycle [57]. Normal cilia beatforward and backwards within the same plane, with no sideways recovery sweep. Recent advancesin computer image processing software may help standardise measures of waveform and directionof multiple cilia, as a measure of the effectiveness of ciliary transport [58, 59]. This software may

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also efficiently compute ciliary activity with accuracy and reproducibility. CBF and beat patternabnormalities have been associated with specific ultra-structural defects such as isolated outer armdefects, isolated inner arm or radial defects or transposition defects [58]. If patients have both anormal CBF and a normal beat pattern, then classic PCD can reasonably be excluded. However, if one or the other is abnormal, further studies are necessary. As with any studies of cilia structureand function, it is critical to exclude ongoing inflammation as a cause of secondary ciliary dysfunction leading to false positives [5].

Ciliary structure

In patients with an appropriate phenotype, suspicion for PCD for other reasons (for example,respiratory symptoms and a sibling with disease) or positive screening tests (saccharin test, nasalNO or CBF abnormalities), the axonemal structure of the respiratory cilia should be studied usingtransmission electron microscopy (TEM) [8]. Inflammatory influences can be avoided by sampling the patient in a stable state, post-antibiotics or, if in vitro testing, by culturing theepithelial cells in an inflammation-free environment. The yield may be higher in patients withsino-pulmonary symptoms rather than isolated upper or lower respiratory tract symptoms [60].

There are a number of structural phenotypes associated with PCD [61]. Most cases of PCD are dueto a lack of ODA, or a combined lack of both IDA and ODA [21]. Less common defects includeIDA defects alone or defects in combination with radial spoke defects, or central microtubule pairdefects such as transposition or central microtubular agenesis [62–64]. In a proportion of patientswith PCD, no structural defects were defined using existing TEM techniques [53, 60]. This, despitea strong phenotype, defined ciliary functional abnormalities and demonstrated genetic defects,underscoring the notion that the disease is almost certainly under-diagnosed, due to the hithertoreliance on TEM as the ‘‘gold standard’’ for diagnosis of the disease. As seen later, advances inmolecular techniques will probably allow a broader definition of PCD (classic and non-classicPCD, akin to the situation with CF), leading to more efficient diagnosis with subsequent beneficial

downstream effects for earlier diagnosis, treatment and improved long-term clinical outcomes.

Immunofluorescent stains

Immunofluorescent analysis using antibodies directed against the main axonemal components hasrecently been used to facilitate identification of structural abnormalities of cilia, and is used indiagnosis in some centres in Europe [65, 66]. PCD patients with ODA defects have absence of DNAH5 staining from the entire axoneme and accumulation of DNAH5 at the microtubule-organising centre as compared with normal individuals with normal DNAH5 staining along theciliary axoneme [66]. Recent work has also shown that antibody-based techniques can diagnose

not only ODA but also IDA abnormalities caused by KTU mutations in PCD [67]. In the future, itmay be possible to develop a panel of antibodies directed towards multiple ciliary proteins thatmay enable the screening of respiratory epithelial samples.

Genetic testing

Overview

As the molecular underpinnings and the genetics of PCD become more defined, genetic testingmay overcome some of the drawbacks of the currently available diagnostic tests. Given the

complexity of ciliary structure and the genetic heterogeneity of PCD, finding gene mutationscausative for PCD has been challenging. Fortunately, non-human models have helped in theprocess of discovery. Since the basic structure of cilia is highly conserved across species, anexample being a simple green alga, Chlamydomonas reinhardtii , extensive information has beengleaned regarding the structure, function and genetics of human cilia, specifically identifyingcandidate proteins and genes from mutant Chlamydomonas that are critical for normal ciliary function(e.g. slow swimmers with ODA defects and mutant c-heavy chain dynein) [68]. Initial mutations

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found using the candidate gene approach include mutations in DNAI1, homologous to theChlamydomomas genes IC78. This was discovered in PCD patients with ODA defects andfunctional ciliary abnormalities [69, 70]. Since then, there have been several more PCD-causinggene mutations published, using a variety of approaches (table 2). Homozygosity mapping in largefamilies that may or may not be consanguineous, but have multiple affected and unaffected siblingscan be successfully used to identify disease-causing genes. This method utilises the marker analysisto look for the shared region of the genome from affected and unaffected individuals, to identify thechromosomal locus/loci shared between the affected siblings. Genes within the shared locus/loci arecandidates, which can be further aided by the candidate gene approach to prioritise the genes to betested from the shared locus. OMRAN et al. [91] successfully used this method to localise the sharedlocus in affected individuals from a large consanguineous family and identified mutations in theDNAH5 gene. Genome-wide linkage analysis, another approach to find disease-causing mutations,using 31 multiplex families with PCD failed to identify disease-causing genes [92]. The mainlimitation of genome-wide linkage analysis is the extensive genetic and ultra-structuralheterogeneity in PCD that limits the comparison of data across the families to get meaningfullog of odds (LOD) genetic linkage scores that helps indicate the possible disease-causing loci. Othermethodologies include the comparative computational analysis approach, which identifiescandidate genes using the DNA information collected from various sequencing projects fromvarious distinct species. It assumes that higher-level organisms independently lost certain geneticinformation during evolution once the information coding for the specific processes was obsolete.Using subtraction analysis it is possible to find candidate genes necessary for cilia formation andfunction by comparing the genome of a ciliated eukaryote with eukaryotes not dependent on cilia[93, 94]. A comprehensive discussion of the molecular basis of PCD is beyond the scope of thischapter; the reader is referred to KNOWLES et al . [4].

DNAI1 and DNAH5 are associated with ODA defects in PCD

Mutations in DNAI1 and DNAH5 [69, 70, 71–73, 76–78] that encode dynein axonemalintermediate chain 1 and heavy chain 5, respectively, have been well documented in several studiesas causative for PCD. DNAI1 accounts for ,2–10% of patients with PCD, although if one‘‘selected’’ the phenotype to include patients with ODA defects alone, this increases to ,4–14%.

Table 2. Primary ciliary dyskinesia-causing genes in humans showing extensive locus heterogeneity

Human gene Chromosomal

location

Axonemal

component

Ultra-structure of

patients with mutations

[Ref.]

DNAI1 9p13.3 ODA IC ODA defects [69–73]

DNAI2 7q25 ODA IC ODA defects [74, 75]DNAH5 5p15.2 ODA HC ODA defects [76–78]

DNAH11 7p21 ODA HC Normal ultra-structure [79–83]

TXNDC3 7p15.2 ODA IC/LC ODA defects [84]KTU/PF13 14q21.3 Cytoplasmic# ODA +IDA defects [67]

LRRC50 16q24.1 Cytoplasmic# ODA +IDA defects [85, 86]

CCDC39 3q26.33 Ciliary Axoneme Axonemal disorganisation [87, 88]

CCDC40 17q25.3 Ciliary axoneme Axonemal disorganisation [87, 89]RSPH4A 6q22.1 RS Transposition defect [90]

RSPH9 6p21.1 RS CP defects and normal

ultra-structure

[90]

DNAI1: dynein, axonemal, intermediate chain 1 gene; DNAI2 : dynein, axonemal, intermediate chain 2 gene;DNAH5 : dynein, axonemal, heavy chain 5 gene; DNAH11: dynein, axonemal, heavy chain 11 gene; TXNDC3 :

thioredoxin domain containing 3 (spermatozoa) gene; KTU/PF13 : Kintoun; LRRC50 : leucine-rich repeat

containing 50; CCDC: coiled-coil domain containing; RSPH4A : radial spoke head 4 homologue A gene;RSPH9 : radial spoke head 9 homologue; ODA: outer dynein arm; IC: intermediate chain; HC: heavy chain; LC:light chain; RS: radial spokes; IDA: inner dynein arm; CP: central pair. #: cytoplasmic protein required for the

dynein arms assembly.

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The commonest mutation (founder mutation) in DNAI1 is IVS+2_3insT, accounting for .50% of mutations. DNAH5 is a heavy chain dynein and mutations in the gene were initially found in alarge inbred family of Arab descent. Subsequent studies show mutations in DNAH5 to be presentin ,15–28% of patients with PCD. Together therefore, DNAI1 and DNAH5 account for ,20–40%of patients with classic disease with ODA defects. Despite extensive allelic heterogeneity, fourexons in DNAI1 and five exons in DNAH5 represent mutation clusters, which became the basis of development of the clinical genetic testing for PCD.

Miscellaneous other mutations associated with PCD

Mutations have been identified in other genes in patients with PCD, specifically, DNAH11, DNAI2 ,KTU , RSPH9 , RSPH4A, TXNDC3 and LRRC50, CCDC39 and CCDC40 (table 2) [26, 67, 74, 79–81,84, 85, 88–90]. Some genotype–phenotype associations have been defined amidst the plethora of mutations found, primarily at the ultra-structural level (rather than at the clinical level). Mutationsin DNAH5 , DNAI1 and DNAI2 are exclusively seen in patients with ODA defects, whereasmutations in KTU and LRRC50 are exclusively seen in patients with combined ODA+IDA defects[4]. The genetics of the DNAH11 (which encodes dynein axonemal heavy chain 11) mutation are

quite interesting as it was found in a patient with proven CF and situs inversus . It was not clear if thispatient had PCD/Kartagener syndrome, or isolated situs inversus , as there is an obvious phenotypicoverlap between the CF and PCD. However, the patient had abnormal ciliary beat pattern as seen inPCD, normal ciliary ultra-structure, but with a mutation in the DNAH11 gene that was assumed tobe linked to the situs inversus [95, 96]. Subsequently, mutations in DNAH11 were unequivocally shown to be PCD causing in a large German kindred and more recently two patients with PCD werefound to harbour mutations in DNAH11 [80, 81]. All of the patients with DNAH11 mutationspresented with normal dynein arms. This phenotype highlights the difficulty in diagnosis in thosepatients with a strong clinical phenotype, but with normal cilia on TEM analysis. Mutations inDNAI2 that encode for a dynein axonemal intermediate chain 2 have been identified in 4% of PCD

patients with ODA defects [79]. In contrast to the above proteins and genes, which encode fordynein proteins, KTU is a cytoplasmic protein, required for the assembly of the dynein complex [67]. First noted to be mutated in Mekada fish with laterality defects, and subsequently Chlamydomonas , it was then found to be mutated in PCD patients with both IDA and ODA defects(logical since it is required for normal ODA and IDA assembly and transportation). Mutations inKTU are seen in ,12% of PCD patients with combined ODA and IDA defects. RSPH9 , whichencodes for the radial spoke head protein 9, was identified as being a PCD-causing gene usinghomozygosity mapping in two Arab Bedouin families. Subsequently, an identical homozygous 3-bpinframe deletion mutation was identified in both families. Interestingly, the ultra-structure analysisof patients from one family depicted 9+2 or 9+0 microtubular configuration, and from the other

family normal ciliary ultra-structure was seen [90]. Using homozygosity mapping in three inbredPakistani families, RSPH4A was identified as a PCD-causing gene that encode another radial spokehead protein 4A. Ultra-structural analysis showed transposition defects with the absence of a centralpair and 9+0 or 8+1 configuration. TXNDC3 (encoding thioreduxin domain-containing protein 3)is a component of the sperm flagella ODA, and a nonsense mutation on one allele and a splicemutation on the other allele were found in one PCD patient [84]. Large genomic deletions, as wellas point mutations involving LRRC50 (leucine-rich repeat containing 50), are responsible for adistinct PCD variant that is characterised by a combined defect involving assembly of the ODA andIDA. Functional analyses shows that LRRC50 deficiency disrupts assembly of distally andproximally DNAH5 and DNAI2 containing ODA complexes, as well as DNALI1-containing IDA

complexes, resulting in immotile cilia [85]. Multiple other candidate genes have been tested inpatients and families with PCD, and were found to be negative.

Other genetic associations

X-linked retinitis pigmentosa, sensory hearing deficits and PCD have been associated via mutations in the RPGR, essential for photoreceptor maintenance and viability [41]. In addition, a

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single family was reported with a novel syndrome that is caused by oral-facial-digital type 1 gene(OFD1) mutations, and characterised by X-linked recessive mental retardation, macrocephaly andPCD [45].

Future directions

Animal models for PCD have been reported to occur in nature, although they have rarely been

studied in depth [97]. Similarly animals with a PCD phenotype have been constructed usingmolecular techniques, mainly in mice [4]. Other than the Mdnah 5 deficient mouse and the Dpcd/

poll knock out mouse, the causative gene in the other models are unknown. The Mdnah 5 deficientmice were created via transgenic insertional mutagenesis that leads to a frame shift mutation. Themice have the classic PCD phenotype and the ultra-structural analysis reveals absent ODA [98,99]. The Dpcd/poll knock out mice present a phenotype of sinusitis, situs inversus , hydrocephalus,male infertility and ciliary IDA defects [43]. Recently, a murine mutation of the evolutionarily conserved adenylate kinase 7 (Ak7) gene resulted in animals presenting with pathologic signscharacteristic of PCD, including ultra-structural ciliary defects and decreased CBF in respiratory epithelium [100]. The mutation is associated with hydrocephalus, abnormal spermatogenesis,

mucus accumulation in paranasal passages and a dramatic respiratory pathology upon allergenchallenge. Ak7 appears to be a marker for cilia with 9+2 microtubular organisation. Mutations of the human equivalent may underlie a subset of genetically uncharacterised PCD, although nohuman mutations have been identified as yet. Finally, a novel method of developing a mousemodel with a PCD phenotype was recently published [101]. A transgenic mouse lacking an ODAwas developed by deleting Dnaic1, a mouse intermediate chain dynein. Importantly, the mice didnot develop many of the problems that usually result in an early death for the animals, such ashydrocephalus or other severe developmental defects. Thus, the survival of the animals allowed theinvestigators to show that the animals did experience problems consistent with defective MCC, atleast in the upper airway (severe rhinosinusitis). Objective measures of MCC were also consistent

with defective ciliary function in the nasal passage, though interestingly not in the lower airway,possibly reflecting differing turnover of ciliated epithelium in various regions of the respiratory tract (upper versus lower). This animal model may allow studies that attempt to dissect out therelative importance of the various components of the MCC apparatus in different airway regions.

Summary: an algorithm for testing

As there is no easy, single diagnostic test to diagnose PCD, it is recommended that the diagnosis bebased on multiple contributing pieces of data (fig. 2). A typical clinical presentation to suggestadditional testing for PCD includes recurrent respiratory tract infections (either upper or lower, or

both), neonatal respiratory distress, childhood ear infections, adult bronchiectasis in the absenceof a diagnosis and male/female fertility problems. Additional features to provoke further testsinclude organ laterality defects, and complex congenital heart or other organ defects and retinitispigmentosa. Ciliary dyskinesia, sperm immotility or identification of specific defects of axonemalstructures on electron microscopy are also suggestive of the diagnosis. The reader should bear inmind that patients with PCD with atypical histories may have no demonstrable ciliary ultra-structural defects on standard TEM. Nasal NO, if available, helps exclude the disease if normal orvery high and, if very low, strongly suggests the diagnosis. Recently, clinically available genetictesting, a rapidly evolving field, may assist in an increasing number of patients with PCD.

Therapeutic approaches

Overview

The goal for the management of PCD is to prevent exacerbations and complications as much aspossible, and to slow the progression of disease. As the disease is generally not as severe as CF, and

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the diagnosis may be delayed, adults with the disease may not fully appreciate or understand thenature and/or severity of the disease. Thus, education as to the diagnosis, prognosis andtherapeutic avenues need to be discussed thoroughly with the patients once the diagnosis is secure(usually on several occasions). Although there are few literature-based studies in PCD, there areenough studies in CF and non-CF bronchiectasis to allow significant extrapolation (although nottotal, see later) into patients with PCD, to at least frame a plan of treatment depending on diseaseseverity, sputum microbiology and patient circumstances. Medical therapy has been shown to slow

the deterioration in lung function [20, 102]. ELLERMAN and BISGAARD [20] reported longitudinallung function in 24 patients diagnosed before and after the age of 18 years. They observed worselung function in patients diagnosed in adulthood, but did not find further deterioration in lungfunction in either group once the diagnosis was established and routine care initiated. Thissuggests that aggressive treatment could prevent further lung damage. It should be noted, however,that other larger patient cohorts followed for a longer time period suggest that PCD may be aserious threat to lung function as early as pre-school, with a high degree of variation in the loss of lung function once diagnosed [103]. There was no link to either age or level of lung function atdiagnosis and early detection did not slow the rate of decline in lung function. These data supportthe genetic and phenotypic heterogeneity of PCD. Despite this, regular clinical surveillance is

strongly recommended to establish trends of disease progression, and to detect exacerbations early to attempt to prevent irreversible lung damage. This should include at least lung function testing,sputum or throat cultures to assess airway microbiology and annual chest radiographs [104].Pulmonary function in PCD patients appears to decline slower compared with patients with CFand the majority of patients with PCD seem to have a normal to near normal life span [21].However, there are patients that develop progressive bronchiectasis, leading to severe lung diseaseand respiratory failure.

Specific therapies

There are no therapies to date that have been shown to correct ciliary dysfunction in PCDpatients. Some pilot or single case reports suggest benefit for some of the underlyingpathogenetic pathways in PCD, but none are yet available on a general basis, or proven inrandomised controlled studies (although patients will often inquire as to their availability)[33, 105, 106]. Thus, therapies to enhance airway clearance, as well as to suppress or kill bacteriaare the cornerstones to PCD care.

Airway clearance

As with CF, routine airway clearance with cardiovascular exercise, percussion vests, chest physical

therapy and various valve/positive expiratory pressure devices should be performed on a daily basis. The aims of respiratory physiotherapy include mobilising and aiding expectoration of broncho-pulmonary secretions, improving efficiency of ventilation, maintaining or improvingexercise tolerance, improving knowledge and understanding and reducing breathlessness and chestpain. There are no data in either CF or PCD to support any one method of airway clearance overanother, and in adults a good practice is to facilitate a consultation with a chest physiotherapist foran education ‘‘class’’, and to determine what modality of airway clearance and what devices thepatient prefers. As with any chronic lung disease, exercise is highly recommended forcardiovascular fitness and specifically for airway clearance. Even though a chronic cough is amajor complaint, it should not be suppressed as it is a compensatory mechanism for mucusclearance with dysfunctional cilia [33].

Antibiotics

Antibiotics are the mainstay of treatment for bacterial infections of the airways associated withPCD. The microbiological flora of the airways is broadly similar to that of CF, although with adelayed appearance of P. aeruginosa . Antibiotic therapy should be based on regular sampling of

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airway secretions for Gram-positive, Gram-negative and acid fast pathogens to build a pattern of the main pathogens in any given patient’s airways [21, 107]. In adults, sputum is usually easy toacquire and bronchoscopy is not usually necessary to gather specimens. When PCD patients havesymptoms of a respiratory tract infection, they require treatment with antibiotics based on airway cultures and sensitivities. H. influenzae, S. aureus , and S. pneumoniae are commonly isolated fromthe airways of PCD patients. There are no randomised placebo-controlled studies evaluating theefficacy of antibiotics in exacerbations in adults or children although numerous studies indicate

that antibiotics can improve symptoms and hasten recovery. Antibiotics are recommended forexacerbations that present with an acute deterioration (usually over several days) with worseninglocal symptoms (cough, increased sputum volume or change of viscosity, increased sputumpurulence with or without increased wheeze, breathlessness and haemoptysis) and/or a decrease inlung function based on lung function testing. Expert consensus is that 2 weeks of therapy isreasonable. The choice of antibiotics may be initially empirical, based on the likely microbial agentor guided via previous sputum cultures in an individual (hence the recommendation to gatherserial samples). The recommended route of antibiotics needs further study to address the optimalregimen, but most clinicians use oral antibiotics for milder exacerbations and combined anti-pseudomonal intravenous drugs for more significant deteriorations. Previous studies suggest that

the combination of intravenous and inhaled antibiotics might have greater efficacy thanintravenous therapy alone [34]. In patients chronically colonised with P. aeruginosa , the additionof nebulised tobramycin to high-dose oral ciprofloxacin for 14 days led to a greater reduction inmicrobial load at day 14 although there was no clinical benefit [108]. Attempts at early eradicationof newly acquired bacteria are recommended as in CF, although there are no data that show thatsuch an approach prevents the progression of lung disease. Long-term antibiotics or nebulisedantibiotics (tobramycin, colomycin or aztreonam) may be used in patients with chronic orfrequent exacerbations. Some patient do well on ‘‘rotating’’ cycles of oral antibiotics, althoughthere are no data to support such an approach and there is a general concern about incitingmicrobial resistance.

Modulation of airway secretions

In the CF population, nebulised hypertonic saline (7% hypertonic saline) is beneficial by modulating the liquid content of the periciliary fluid layer, thereby thinning thick secretionsand triggering a cough reflex [109, 110]. However, in PCD, its utility is less clear as itstimulates cough to help clear secretions but its role in thinning secretions is not known [111].A small study of 24 patients with non-CF bronchiectasis showed that hypertonic saline resultedin greater expectorated sputum weight and a greater reduction in sputum viscosity comparedwith the active cycle of breathing technique alone [112]. Thus, it may be considered in the

PCD population as it can augment mucus clearance with little to no risk, other than time.Other aerosolised hypertonic agents such as dry powder mannitol are currently beinginvestigated and may be promising in the future [113]. Deoxyribonuclease (dornase alfa), anenzyme that hydrolyses eukaryotic DNA released from decaying neutrophils to diminishmucus viscosity and enhances clearance, is beneficial in CF patients, but its use by extrapolation into PCD patients remains unproven and may even be detrimental to lungfunction [114, 115].

Other airway treatments

Bronchodilators are not particularly effective in PCD or CF unless a coexisting asthmaticcomponent exists [116]. PCD patients may be initially misdiagnosed as asthmatics unresponsive toconventional therapy, including b-agonists and inhaled corticosteroids. b-Adrenoceptor agonistshave been shown to augment CBF in functional cilia but there is little data in the dyskinetic ciliaseen in the PCD population [117]. Anti-inflammatory strategies such as alternate-day prednisolone have not been shown to be effective in CF; there are no studies in PCD [118].Inhaled steroids may or may not be of benefit in individual patients with PCD; a recent Cochrane

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review concluded no benefit in non-CF bronchiectasis overall [119]. As with other inflammatory diseases of the lung, the macrolide antibiotics may exert long-term benefits for the modulation of airway inflammation and thus disease expression [106, 120].

Miscellaneous lung treatments

L-Arginine might hypothetically have a therapeutic role in PCD patients, in augmenting the

production of airway NO, theoretically enhancing CBF (although the exact role of NO in thisprocess is unknown). However, in the small studies performed, L-arginine did not normalise nasalNO levels and no improvement in lung function was observed [121]. Uridine-5-triphosphate(UTP), or its analogues, is also a potential therapy for CF and similar diseases [122]. UTPstimulates chloride ion secretion and mucin release in goblet cells, therefore increasing airway fluidhydration and enhancing cough clearance in healthy individuals. A small acute clinical trial of nebulised UTP in PCD demonstrated enhanced airway clearance during cough, but no long-termbenefits in pulmonary function have been shown [33]. Localised surgery may be considered insituations that resemble that of CF or idiopathic bronchiectasis, where occasionally very localisedlung disease is considered to be problematic in causing severe systemic symptoms, frequent

exacerbations and/or life threatening haemoptysis [123, 124]. Patients with such localised disease,haemoptysis or refractory pulmonary infections, have undergone surgical resection of thebronchiectatic lung but the long-term effects are unknown [124]. If PCD does progress to end-stage lung disease, lung transplantation must be considered. PCD patients have undergonesuccessful heart-lung, double lung or living donor lobar lung transplant [125]. In patients withsitus inversus , the anatomic disorientation adds an extra challenge when considering theanastomotic sites but is not a contraindication. The long-term survival appears similar to otherlung transplant recipients.

Treatment of extrapulmonary disease in adults

As PCD affects other aspects of the respiratory tract other than the lungs, treatment of those areasmust be considered. Chronic rhinitis and sinusitis may cause significant morbidity in patients withPCD. As of now, no treatments have been shown to be unequivocally effective, although mostpatients are treated with intranasal corticosteroids, sinus lavage procedures and antibiotics.Antibiotics should be used sparingly for sinus symptoms as resistance occurs quickly andantibiotics should be reserved for more pressing pulmonary symptoms. If sinus symptoms persistdespite aggressive medical management or are severe, endoscopic sinus surgery can be used topromote drainage and better delivery of topical medications [126]. Male infertility due to spermimmotility can be overcome by assisted fertilisation techniques such as intracytoplasmic sperminjections [127]. Females, who are infertile secondary to fallopian tube dysfunction, can havedirect ovum harvesting from the ovaries and can get in vitro fertilisation.


P.G. Noone is principal investigator on an industry sponsored study (multicentre) looking at theeffects of inhaled mannitol in non-cystic fibrosis bronchiectasis (Pharmaxis). He is also principalinvestigator on an industry sponsored study (multicentre) looking at the effects of inhaledaztreonam in non-cystic fibrosis bronchiectasis (Gilead).

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CD000996.

120. Saiman L, Marshall BC, Mayer-Hamblett N, et al. Azithromycin in patients with cystic fibrosis

chronically infected with Pseudomonas aeruginosa : a randomized controlled trial. JAMA 2003; 290:

1749–1756.

121. Grasemann H, Gartig SS, Wiesemann HG, et al. Effect of L-arginine infusion on airway NO in cystic fibrosis andprimary ciliary dyskinesia syndrome. Eur Respir J 1999; 13: 114–118.

122. Deterding RR, Lavange LM, Engels JM, et al. Phase 2 randomized safety and efficacy trial of nebulized denufosol

tetrasodium in cystic fibrosis. Am J Respir Crit Care Med 2007; 176: 362–369.

123. Balkanli K, Genc O, Dakak M, et al. Surgical management of bronchiectasis: analysis and short-term results in

238 patients. Eur J Cardiothorac Surg 2003; 24: 699–702.

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124. Smit HJ, Schreurs AJ, Van den Bosch JM, et al. Is resection of bronchiectasis beneficial in patients with primary

ciliary dyskinesia? Chest 1996; 109: 1541–1544.

125. Rabago G, Copeland JG III, Rosapepe F, et al. Heart-lung transplantation in situs inversus . Ann Thorac Surg 1996;

62: 296–298.

126. Parsons DS, Greene BA. A treatment for primary ciliary dyskinesia: efficacy of functional endoscopic sinus

surgery. Laryngoscope 1993; 103: 1269–1272.

127. Gerber PA, Kruse R, Hirchenhain J, et al. Pregnancy after laser-assisted selection of viable spermatozoa

before intracytoplasmatic sperm injection in a couple with male primary cilia dyskinesia. Fertil Steril 2008; 89:

9–12.

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Chapter 10

Channelopathies in

bronchiectasisI. Sermet-Gaudelus* ,#,",+, A. Edelman* ,# and I. Fajac* ,+,1

Summary

Channelopathies are diseases caused by dysfunction of ion

channel subunits. They result in impaired mucociliary clearanceand may therefore lead to bronchiectasis.

The main channelopathy associated with bronchiectasis iscystic fibrosis (CF), an autosomal recessive disease caused by mutations in the CFTR gene, which encodes the chloride CFTR channel.

Bronchiectasis can be associated to channelopathies infollowing cases: 1) patients with already known typical CF; 2)patients with bronchiectasis who, on investigation, are found

to have a single-organ manifestation of CF; 3) patients withonly one or none mutation of CFTR with abnormal sweat testor nasal potential difference (PD) where CFTR mutations play the role of a modifier deleterious gene; and 4) patients withonly one or no mutation of CFTR with normal sweat test ornasal PD, who may still have an undefined channelopathy. Inthese last two cases, it may be that, CFTR mutation combined with another ion transport abnormality, in a situation of transheterozygosity, creates the conditions for abnormalairway surface liquid (ASL) hydration regulation and defectivemucociliary clearance.

Keywords: Airway surface liquid, bicarbonate, calcium-dependent chloride channel, cystic fibrosis, cystic fibrosistransmembrane conductance regulator, epithelial sodiumchannel

*Universite Paris Descartes,#INSERM Unite 845,"

Service de PneumoPediatrie, HopitalNecker-Enfants Malades,+Assistance Publique Hopitaux deParis, and1Service de Physiologie-ExplorationsFonctionnelles, Hopital Cochin,Paris, France.

Correspondence: I. Sermet-Gaudelus,Service de PneumoPediatrie,Universite Paris Descartes, HopitalNecker-Enfants Malades, 149 rue deSevres, 75015, Paris, France, [email protected]


Bronchiectasis is defined as an abnormal dilation of proximal medium-sized bronchi due to

weakening or destruction of the muscular and elastic components of the bronchial walls [1]. Itis caused by a vicious cycle of transmural infection and inflammation, resulting in retainedsecretions that damage the airways and impair mucociliary clearance.

Bronchiectasis can appear as either a local obstructive process or a diffuse disease involving bothlungs. In the latter case, a systemic condition must be sought. These can include autoimmunedisease, a1-antitrypsin deficiency, connective tissue disorders, immunodeficiency states, allergic

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bronchopulmonary aspergillosis and primary ciliary dyskinesia. Channelopathies, defined asdiseases caused by dysfunctioning ion channel subunits, are another possibility. Channels arepore-forming proteins that provide pathways for the controlled movement of ions into or out of cells, and are hence important in regulating mucociliary clearance [2]. The present chapter focuseson the role of channelopathies as causative factors for the development of bronchiectasis.

The link between ion transport and mucus transport inthe airways

Two opposing transport systems tailored to controlling the volume of liquid on theepithelial surface

The thin film of liquid covering airway surfaces, called airway surface liquid (ASL), is partitionedinto two compartments, the mucus layer, which entraps particles and pathogens and has lubricantactivity, and the periciliary liquid (PCL) layer, which facilitates ciliary beating and separates themucus layer from the mucins tethered to the cell surface [3]. Normal airway surface epithelia can

regulate ASL volume by setting the height of the PCL to approximately the height of the extendedcilia (,7 mM) [3]. The coordination of sodium and chloride ion transport regulates ASLhomeostasis to provide efficient mucus transport.

Under resting conditions, airway surface epithelia display net salt and fluid absorption (fig. 1),driven by active apical Na+ absorption through the amiloride-sensitive epithelial sodium channel(ENaC), passively accompanied by Cl-, in part, via a transcellular pathway, mainly the cysticfibrosis transmembrane conductance regulator (CFTR), and, in larger part, via the paracellularpathway [3]. This absorptive pattern occurs due to basolateral sodium–potassium adenosinetriphosphatase (Na+,K+-ATPase), which generates an electrochemical gradient favourable forapical Na+ absorption. ASL remains isotonic under basal conditions because of the airway

epithelium’s permeability to water (due to the relative leakiness of the tight junctions) and the iso-osmotic conditions of ion transport.

When ASL volume is depleted, normal airway epithelium exerts dynamic regulation by switching itsstatus from net NaCl absorption to net secretion (fig. 2) [3, 4]. This requires the accumulation of Cl-

within the cell through the action of the Na+/K+/2Cl- cotransporter located in the basolateralmembrane. Cl- then exits the cellacross the apical Cl- channels, at thesame time as apical Na+ absorptionslows and Na+ moves paracellu-

larly to maintain electroneutrality.Adenosine triphosphate (ATP), re-leased on to the airway surface, isthe main sensor for this regulation[5]. Its actions are mediated by twopurinergic receptor subtypes, thepertussis-toxin-insensitive G-pro-tein (Gq)-coupled ATP/uridine tri-phosphate (UTP)-sensing P2Y2

P2Y receptor and the stimulatory

G-protein (Gs)-coupled A

2B

adeno-sine receptor. Activation of the A2B

purinoreceptor raises cell cyclic ade-nosine monosphosphate (cAMP),which, in turn, activates the CFTR sufficiently to provide CFTR-depen-dent Cl- secretion and negative ENaC

K+

Na+

Cl-

Na+

ENaC

Cl-

Luminal Basolateral

Cl-

Cl-

CFTR PKA

K+ Na+, K+-ATPase

+

-

Figure 1. Cellular models of electrolyte secretion: absorption

pathway. In airway epithelial cells, under resting conditions, Na+ is

taken up by a luminal epithelial sodium channel (ENaC); Cl-

istransported via the paracellular shunt and probably via cystic fibrosis

transmembrane conductance regulator (CFTR) Cl- channels. Na+ is

pumped out of the cell by the basolateral sodium–potassiumadenosine triphosphatase (Na+,K +-ATPase), whereas Cl- and K +

leave the cell via Cl- and K + channels, respectively. PKA: protein

kinase A. -: inhibition; +: stimulation.

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E T A L .



regulation by the CFTR. Higher ATPconcentrations then activate the P2Y2

receptor, promoting, on the onehand, the inhibition of Na+ absorp-tion and, on the other, Cl- secretion,mediated by another apical channel,the calcium-activated chloride chan-

nel (CaCC).

Finally, when ASL volumes are de-pleted, the epithelium rehydrates air-way surfaces by: 1) inhibiting absorp-tion (in the surface epithelium); and2) activating secretion (in the sub-mucosal glands).

Ion transporters involved in

mucociliary clearance

Consistent with these fundamentalobservations, most of the chan-nelopathies identified as possiblecauses of the impaired clearance of bronchial tree secretions appear toinvolve Cl-, Na+ and bicarbonatetransport.

Cl -

transporters

Cystic fibrosis transmembraneconductance regulator

The CFTR is a member of theATP-binding cassette transportersuperfamily, principally expressed

in the apical membrane of epithelia. It plays a fundamental role in transepithelial fluid andelectrolyte transport because it functions as an anion channel and a regulator of ion transporters

in epithelial cells. The CFTR is a cAMP- and ATP-regulated Cl-

channel that permits Cl-

to bereleased from the cell [6]. Recent data also suggest that the CFTR pore may switch dynamically from a conformation permeable to Cl- to a conformation permeable to large anions, such asglutathione and HCO3

-, and may, therefore, be involved in pH regulation of the ASL andmucus [7].

Apart from its secretory function, the CFTR has the regulatory function of other epithelialchannels. The CFTR inhibits ENaC activity and, therefore, conveys reduction in Na+

resorption [8]. The CFTR upregulates an outwardly rectifying chloride channel (ORCC)following its activation by protein kinase A (PKA) [9]. The CFTR can also interact via itsextreme C-terminal amino acid sequence with PDZ-domain-containing proteins, which areimportant organisers for receptors, ion transporters and regulatory elements present in air-way epithelium [10]. For example, reciprocal activation between the CFTR and the solutecarrier (SLC) 26 transporter (SLC26T) family of HCO3

-/Cl- exchangers has been shown todepend upon PDZ domain interaction and binding of the sulfate transporter and anti-sfactor antagonist (STAS) domain of SLC26T family proteins to the CFTR regulatory (R)domain [11].

Apical Basolateral

Na+ H2O

Na+

Cl-

HCO3

-

-

AdenosineATPUTP

Cl-

Na+ H2O

PKAcAMPCa2+

K+

K+

KV7.1

KCa3.1

K+

Na+

2Cl-

K+Na+, K+-ATPase

CaCC

ENaC

Na+ /K+ /2Cl- cotransporterCFTR

Figure 2. Cellular models of electrolyte secretion: secretorypathway. In airway cells, under conditions triggering secretion, Cl-

is taken up from the basolateral (blood) side by the Na+ /K + /2Cl-

cotransporter. K + recycles through basolateral K + channels. This

leads to basolateral membrane hyperpolarisation, which, in turn,electrically drives Cl- to the luminal side of the epithelium and

stimulates Cl- secretion through the cystic fibrosis transmembraneconductance regulator (CFTR) and/or calcium-activated chloride

channels (CaCCs). Activation of the A 2B adenosine receptor results

in raised cell cyclic adenosine monosphosphate (cAMP) levels,which, in turn, activate the CFTR sufficiently to provide CFTR-

dependent regulation of the epithelial sodium channel (ENaC) and

Cl- secretion, together with activation of the cAMP-dependent

potassium channel (K V 7.1). Higher ATP concentrations activate theP2Y 2 P2Y receptor, inhibiting Na+ absorption and activating both

CFTR-dependent and CFTR-independent Cl- secretion, the latter

mediated by the release of cytoplasmic Ca2+, which, in turn,activates the CaCC and the calcium-activated potassium channel

(K Ca3.1). Na+ is pumped out of the cell by sodium–potassium

adenosine triphosphatase (Na+,K +-ATPase). Na+ is secreted via the

paracellular shunt following the electrical driving force generated bythe negative transepithelial voltage in the lumen. ATP: adenosine

triphosphate; UTP: uridine triphosphate; PKA: protein kinase A.

q: increased; -: inhibition.

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Calcium-activated chloride channels

Airway epithelial cells display Ca2+-dependent Cl- secretion through CaCCs in response tomucosal nucleosides. The mechanism relies on the stimulation by ATP or UTP of the G q-coupledP2Y2 purinergic receptors, which increases inositol 1,4,5-trisphosphate (IP3) production andsubsequently cytosolic Ca2+ release [12].

Transmembrane protein 16A (TMEM16A), which generates Ca

2+

-activated Cl

-

currents withsimilar biophysical and pharmacological properties to those in native epithelial tissues, is a very likely candidate for these CaCCs [13].

Chloride channel-2

Chloride channel (ClC)-2 is a member of the pH- and voltage-activated chloride channel family and is present on the apical membranes of airway epithelial cells [14]. Activation of ClC-2 ishypothesised to provide a parallel pathway for Cl- secretion [15].

Indirect activation of Cl- secretion by K+ channels

Activation of K+ channels at the basolateral side of the epithelium causes hyperpolarisation of thebasolateral membrane, which electrically drives Cl- to the luminal side of the epithelium andstimulates Cl- secretion through the CFTR and/or CaCCs. At least two different populations of K+

channel are located on the basolateral side of airway epithelial cells that are activated by an increasein either intracellular cAMP (cAMP-dependent potassium channel (KV7.1)) or Ca2+ (calcium-activated potassium channel (KCa3.1)) [16].

Na+ transporters

The ENaC is a heteromultimer composed of distinct but homologous a-, b- and c-subunitsknown to be activated by selective endoproteolysis [17]. As pointed out above, it provides themain pathway for apical Na+ absorption at the apical membrane [3, 4]. The ENaC and the CFTR physically associate in mammalian cells [18], an interaction that may impede ENaC proteolyticcleavage and inhibit stimulation of the channel open probability [19].

HCO3

- transport

HCO3

- plays a critical role in determining the viscosity of mucins and mucus by decondensingmucin granules. Intracellularly, mucins are condensed in granules by high concentrations of Ca2+

and H+ that shield the repulsive forces of the anionic sites of mucin glycoproteins. As granules aresecreted, Ca2+ and H+ have to dissociate quickly from the mucin to unshield the negative sites, sothat Na+ can replace Ca2+ to allow mucin network hydration, swelling and dispersion. HCO3

- iscritical for sequestration of Ca2+ and H+ and maintenance of a low concentration of these freecations in solution, which, in turn, favour their disassociation from mucins [20, 21]. Moreover, anormal pH is necessary for effective mucociliary clearance, as assessed by several observations. Forexample, a reduction in extracellular pH of 0.5 reduces mucociliary beat frequency by 22% inbronchi and 16% in bronchioles [22].

As stated above, the CFTR clearly plays a role in HCO3

- transport. Cell membrane ion transporters

besides CFTR may also be involved in ASL and/or gland fluid pH regulation [23]. These includethe following.

Na+/HCO3

- cotransporters

The basolaterally located isoform sodium bicarbonate cotransporter (NBC) 1 permits the basalinflux of HCO3

- followed by efflux through the apical CFTR [24].

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E T A L .



Cl-/HCO3

- exchangers

Based on an analogy to SLC26A3 function in HCO3

- secretion by the pancreatic duct epithelium,WHEAT et al . [25] proposed a model for HCO3

- transport in the airway epithelium: Cl-/HCO3

-

exchange activity, governed by SLC26A3 in the apical membrane, might secrete HCO3

- into theASL, with Cl- recycling through the CFTR. However, experiments in polarised airway epithelialcells failed to confirm this hypothesis [26]. The role of Cl-/HCO3

- exchangers in ASL pH

regulation at the apical membrane therefore remains speculative.

Investigation of ion transport in airway epithelium

Transepithelial potential difference (PDte) results from ion movements across both the basolateraland apical membrane and leakiness of tight junctions. Its assessment has been applied in vivo toboth nasal and bronchial mucosa [27]. Nasal potential difference (PD)-based outcomes includethe stable maximum baseline (basal PD) and the successive net voltage changes after perfusion of the mucosa with: 1) amiloride (an ENaC inhibitor), to assess Na+ transport (Damiloride); 2) low-chloride solution, to drive Cl- secretion (Dlow-chloride); and 3) isoproterenol in low-chloridesolution (Disoproterenol), to stimulate the cAMP-dependent Cl- conductance related to the CFTR (fig. 3). The sum of Dlow-chloride and Disoproterenol serves as an index of CFTR function [28].

This PDte can also be measured in Ussing chambers, using either epithelial biopsy specimens orairway epithelial cells in culture. This system measures transepithelial ion transport by evaluatingPDte in volts [29], by either applying a PD and measuring the resulting change in current(technique of voltage clamping) or short-circuiting the tissue, i.e. clamping PDte at 0 V andmeasuring the amount of current required.

Channelopathies: cystic fibrosis

Pathophysiology

Cystic fibrosis (CF) is one of the principal channelopathies resulting in abnormal mucus clearance.It is an autosomal recessive disease caused by mutations in the CFTR gene (CFTR ), which encodesthe CFTR Cl- channel [30].

In CF, defects in the mechanisms governing both Na+ absorption and Cl- secretion severely disruptASL volume regulation on airway surfaces. Specifically, they accelerate the basal rate of netepithelial Na+ absorption in CF airway epithelia, causing isotonic volume hyperabsorption that

reflects the absence of the tonic inhibitory effect of CFTR on ENaC activity [31, 32]. Themechanism linking the missing CFTR and increased Na+ absorption in CF airway epithelia may bethe failure to protect ENaC from proteolytic cleavage and consequent activation [33].

CF airway epithelia also lack the capacity to enhance Cl- transport [34]. Therefore, whereas non-CFepithelium can rehydrate when ASL volumes are depleted, by activating secretion and inhibitingabsorption, CF epithelium cannot switch from net absorption to net secretion [31]. This inability may be due to its dependence on ATP signalling alone, in contrast to the dual signalling (ATP andadenosine) systems that control ASL volume in normal epithelia [35]. In this model, ATP can inhibitENaC and activate CaCC, via the P2Y2 receptor, but the A2B pathway is blocked because the CFTR isnot functional. Under resting conditions, the P2Y2 pathway may be sufficient to produce an ASL

volume consistent with mucus transport. It may, however, be overwhelmed in a context of respiratory infections, e.g. virus infections, which are frequent in early life. These infections and theireffect on this system might, therefore, be the initiating event of CF disease [31].

The resultant reduction in ASL volume is shared by the two layers: 1) the water content of themucus layer is reduced, producing a highly viscoelastic adhesive material; and 2) the water contentof the periciliary environment is depleted, causing the collapse of this layer and a loss of its

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C H A N N E L O P A

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lubricant activity. The combinationof the PCL and ASL defects causesthe mucus to adhere to the airway [36]. Evidence of adhesion is avail-able from early pathological studiesof CF airways, which reveal bron-chiolar mucous plugs within 48 hours

of birth [37], and from radioparticledeposition studies that show theinability of the cough manoeuvreto clear mucus adhering to airway surfaces [38].

A recent hypothesis suggests that adefect in HCO3

- secretion plays acritical role in the pathophysiology of CF [39]. As pointed out above,

the level of monovalent cations inASL in CF patients is normal andconstant, whereas it is the concen-tration of HCO3

- that is notably subnormal, because of reducedsecretion due to the CFTR defect[40]. Several studies have shown arelatively acidic ASL [41] and anintrinsic acidification defect in fluidgland secretion in CF [42]. This

reduced HCO3

-

level is associatedwith increased mucus viscosity dueto reduced Ca2+ chelation, necessary for rapid mucin swelling and dis-persion [21]. Importantly, the ex-tent of these defects correlates withthe level of HCO3

-, which suggests arelationship between disease sever-ity and the degree of impairment inHCO3

- secretion [43, 44].

One consequence of mucus stasisis the formation of thick mucousplaques and plugs, in which micro-organisms are embedded. Severalfeatures of this thickened adherentCF mucus promote persistent bio-film growth [45]. First, the increasedconcentration of mucins limits bacterial motility, increases their binding to mucin epitopes and feedsthem. Thus bacteria deposited in CF mucus may proliferate densely in the area of droplet deposition.Secondly, the concentrated mucin gel also limits the effectiveness of secondary defence mechanismsthat might normally resolve a bacterial infection, such as neutrophil migration or diffusion of antimicrobial substances. Finally, cellular oxygen is consumed at high rates in CF airway epitheliumto fuel this increased Na+ transport, thereby creating hypoxic zones in adherent mucous plaques nearthe cell surface that link the special CF low-oxygen environment and infection [46]. Pseudomonas aeruginosa , specifically, adapts to the hypoxic zones by producing alginate and forming biofilm, thussetting the stage for chronic infection. The persistence of chronic bacterial infection of the airway

Ringer

Time seconds

-50

-40

-30

-20

-10

0

BasalPD

∆amiloride ∆low

chloride

∆isoproterenol

∆ l o w - c

h l o r i d

e − ∆ i s o p r o t e r e n o l

BasalPD

∆amiloride

Ringer+amilorideLow chloride+amiloride

Low chloride+amiloride

+isoproterenol

P D

m V

-50a)

b)

-40

-30

-20

-10

0

P D

m V

Figure 3. Nasal potential difference (PD) trace showing theresponse to perfusion of various solutions in a) a healthy control and

b) a cystic fibrosis (CF) patient. Baseline nasal PD (basal PD) is

measured after perfusion of nasal epithelium with saline solution.Nasal PD changes (D) were recorded after perfusion with the

following solutions: 100 mM amiloride in saline solution (Damiloride),

100 mM amiloride in low-chloride solution (Dlow-chloride), and100 mM amiloride plus 10 mM isoproterenol in low-chloride solution

(Disoproterenol). The sum of Dlow-chloride and Disoproterenol

(Dlow-chloride–Disoproterenol) serves as an index of transepithelial

cystic fibrosis transmembrane conductance regulator (CFTR)-

dependent Cl-

transport because it reflects the cyclic adenosinemonosphosphate (cAMP) activation of nasal mucosal Cl- perme-

ability. In CF patients: 1) basal PD is more negative than in healthycontrols because of increased Na+ transport (high depolarisation

following amiloride perfusion); and 2) there is no response following

low-chloride perfusion and isoproterenol administration, showingthe absence of Cl- permeability.

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E T A L .



lumen then stimulates airway defences and induces a chronic hyperinflammatory response, mainly via the nuclear factor (NF)-kB-mediated pathway [47].

Taken together, these findings indicate that the combination of abnormal Na+ and Cl- transport inCF leads to ASL volume regulation failure, mucus stasis, bacterial infection and inflammation.These, in turn, result in inhibition of mucociliary and cough clearance, and, as a final consequence,induction of bronchiectasis.

Clinical description

The diagnosis of CF is based on an abnormal sweat test result (sweat Cl- level of .60 mM) and thefinding of two CF-causing mutations in the CFTR and/or an abnormal PDte [30]. In the lattercase, the response to amiloride is increased because of lack of inhibition of Na+ resorption, and Cl-

secretion is absent in the presence of low-chloride solution and isoproterenol. CF clinicalpresentation can be divided into two types: 1) classic disease, readily diagnosed based on clinicaland laboratory data; and 2) less-severe disease that manifests later in life and yields ambiguousgenetic testing results [48].

In the first case, CF is a life-limiting multisystemic disorder that affects the Cl-

transport system inexocrine tissues. The hallmark is a classic triad of symptoms, most often from infancy orchildhood: progressive obstructive lung disease with sputum infected by Staphylococcus aureus orP. aeruginosa , exocrine pancreatic insufficiency, and a high sweat Cl- level. In males, this triad isassociated with congenital absence of the vas deferens, leading to sterility. Other specific clinicalphenotypes include CF-related liver disease, meconium ileus, CF-related diabetes, pansinusitis andnasal polyposis. Mortality occurs mainly due to progression of lung disease and respiratory insufficiency [49]. In children, bronchiectasis is a marker of respiratory disease severity, because itis associated with increased morbidity and accelerated decline in pulmonary function [50]. It canappear as early as 3 months in CF children [38]. In a cohort of 125 Australian children (from birth

to 6 years) diagnosed with CF after newborn screening, 22% showed evidence of bronchiectasis,and the prevalence increased with age [51]. In the paediatric (but not adult) population, thepresence and severity of bronchiectasis is significantly related to respiratory infection withP. aeruginosa [52], and, more specifically, mucoid P. aeruginosa [53].

In the second case, advances in basic CF science have broadened the clinical spectrum of CF andhighlighted less-severe, so-called CFTR-related, presentations. Most of these patients carry oneCF-causing mutation and one or two mutations retaining residual CFTR function [54]. It is notclear whether CFTR-related bronchiectasis, in such cases, is a single-organ manifestation of CF ora condition in which CFTR mutations play the role of a modifier deleterious gene, acting with anenvironmental contribution.

Several studies [55–66] have investigated the frequency of CFTR mutations in patients withdisseminated bronchiectasis (table 1). The prevalence of CFTR mutations in this population iscontroversial. Four studies [55–58] found no evidence of an increased prevalence of CFTR abnormalities compared with the general population. Other series [57–64] observed very few patients finally diagnosed with CF on the basis of carriage of two CF-causing mutations and/orelevated sweat Cl- levels (approximately 7% of all of the patients enrolled in those studies). Mostpatients had at least one non-CF-causing mutation, including mutations classified as ‘‘associatedwith CFTR-related disorder’’ [54]. Some of these mutations were associated with normalor borderline sweat Cl- levels (substitution of aspartic acid 1152 with histidine (Asp1152His

or D1152H), cytosine to thymidine substitution 10 kb downstream of nucleotide 3849(3849+10 kbC.T), 5T allele of polythymidine tract in intron 8 (IVS8-5T) and Arg117His). Itshould be pointed out that many of the sequence variations identified are not recognised as CFTR mutations, and still less as CF-disease-causing mutations, mainly because of the lack of establishedor substantiated knowledge of their pathogenic potential. In these cases, CFTR functionalevaluation in epithelium might help in identifying patients with CFTR-related disease [28, 66]. Acohort of patients with bronchiectasis and a sweat Cl- level of ,60 mM were investigated [66];

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15 patients carried two CFTR mutations and exhibited abnormal ion transport in the nasalmucosa (i.e. increased Na+ transport and decreased Cl- secretion). They were finally diagnosedwith a CFTR-related disorder. In the same series, 22 patients carried only one mutation butdisplayed abnormal ion transport in the nasal mucosa, intermediate between the normal and theCF range. This led to the hypothesis that an as yet unidentified other factor, genetic orenvironmental, may trigger the pathogenic role of a unique CFTR mutation. Among thepossibilities, abnormalities in ion tranporters other than CFTR should be considered.

Other channelopathies

The epithelial sodium channel

There are two principal, and rare, human clinical disorders that occur due to ENaC mutations[67]. The first is Liddle’s syndrome, caused by gain-of-function mutations leading to enhancedNa+ resorption in the renal tubule, and characterised by volume-expanded low-renin hypertensionand apparently no respiratory disease [68]. The other is pseudohypoaldosteronism (PHA) type I,due to loss-of-function mutations [69]. In addition to kidney impairment, characterised by renalsalt wasting, hyperkalaemia and metabolic acidosis, such children also show defective Na+

transport in the sweat gland, which leads to elevated sweat Cl- and Na+ concentrations. Moreover,

children with PHA-I frequently exhibit respiratory tract diseases that involve increasedmucociliary clearance and decreased mucus viscosity [69].

Recently, ENaCs have been shown to play a critical role in the physiology of mouse airways.Transgenic mice with airway-specific overexpression of the ENaC (b-subunit) develop CF-like lungdisease with mucous obstruction and poor bacterial clearance. The airway surfaces of these miceabsorb three times more Na+, causing ASL volume depletion, increased mucus concentration,delayed mucus transport and increased mucus adhesion to airway surfaces [70]. These events causespontaneous and severe lung disease that shares features with CF, including mucous obstruction,goblet cell metaplasia, neutrophilic inflammation and poor bacterial clearance. This outstandingproof-of-concept study demonstrates that increasing airway Na+ absorption creates all of theconditions for the onset of bronchiectasis and initiates a CF-like lung disease [71]. Further supportfor this mechanism comes from the following two observations: 1) modulation of ENaC activity inCF patients may potentiate disease severity, as suggested by studies showing an enhanced response toamiloride solution in patients with poor respiratory function [72] or chronic P. aeruginosa colonisation [66]; and 2) Na+ transport is significantly higher in bronchiectatic patients, even inthose with no or only one CFTR mutation, compared with control subjects [66].

Table 1. Studies showing an increased prevalence of cystic fibrosis transmembrane conductance regulator

(CFTR) mutation in patients with bronchiectasis of unknown origin

First author [ref.] Subjects n Controls n CFTR mutations

Two One

PIGNATTI [60] 16 Healthy 66; COPD 33; non-

obstructive RD 36; atopic 85

0 4; IVS8-5T: 9

GIRODON [61] 32 0 5 6BOMBIERI [62] 23 Healthy 33 0 11HUBERT [63] 601 0 45 43C ASALS [64] 55 Local historical cohort 0 14; IVS8-5T: 4

ZIEDALSKI [65] 50 0 3 18B IENVENU [66] 122 Healthy 26; obligate heterozygotes 38;

typical CF 9215 22

COPD: chronic obstructive pulmonary disease; RD: respiratory disease; IVS8-5T: 5T allele of polythymidine

tract in intron 8; CF: cystic fibrosis.

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E T A L .



The role of ENaCs in non-CFTR-related bronchiectasis has been investigated in a few studies.SHERIDAN et al . [73] studied 20 patients with diffuse bronchiectasis and elevated sweat Cl-

concentrations but without two CFTR mutations and identified four patients with five missensemutations and one splicing mutation in ENaC genes. Moreover, among 55 patients with idiopathicbronchiectasis who did not have two mutations in the CFTR coding regions, 10 were identified withan ENaC mutation [74, 75]. This was higher than the expected frequency, and, as these variants hadnot been previously described, they are unlikely to be common polymorphisms. Moreover, six

patients showed evidence of abnormal ion transport, in either sweat glands or nasal epithelium.Hence, although these variants were each found in a heterozygous state, they might be expected toresult in abnormal ENaC function. This hypothesis is further supported by recent evidence of ENaCmutations leading to proved channel dysfunction and associated with atypical CF [76].

Other Cl- channels

The model of ASL homeostasis suggests that dysfunction of other Cl- channels may alter ASLhomeostasis. ClC-2 mutations have been identified in people with idiopathic generalised seizures, butthey are not associated with a history of lung disease [77]. Moreover, the ClC-2 knockout mouse

undergoes normal lung development, possibly because it has multiple alternative Cl-

channel con-ductance pathways. A ClC-2 abnormality may, therefore, not be related to any human lung disease [15].

To date, no human disease has been linked to a defect in Ca 2+-dependent Cl- channels. However,mice that do not express TMEM16A, the best candidate for CaCCs, show greatly reducedmucociliary clearance [13]. Therefore, the role of this channel in human bronchiectasis requiresfurther investigation.

Indirect inactivation of Cl- transport

A defect in basal K+ channels may affect the driving force necessary for Cl- to migrate to the apical

membrane, as shown by the strong reduction in Cl- transport in nasal, tracheal and bronchial cellscarrying mutations of KV7.1 and KCa3.1 [16, 78]. However, no lung disease has been reportedamong patients with these channelopathies [16].

Alternatively, defective interaction between an ion transporter and a mutated protein modulatingits function may impair the channel function, as demonstrated for CFTR and SLC26A3. Theinteraction between these two proteins leads to their reciprocal functional activation [11]. WhenSLC26A3 displays a mutation identified in humans, i.e. responsible for congenital Cl- diarrhoea, itsinteraction with the CFTR is altered, and CFTR activation suppressed [11, 79]. Therefore,mutations in proteins that interact with the CFTR, and specifically other SLC26T members, may

affect the CFTR and induce a CF-like phenotype.

Bicarbonate

There is evidence that defective HCO3

- secretion is associated with abnormal mucus hydration andimpaired mucociliary clearance [20]. The amount of mucus discharged is significantly reducedwhen HCO3

- secretion is impeded in the intestines [80] and uterine cervix [43]; a similarmechanism might be anticipated in airways. Extracellular acidification also favours inflammation,by inducing neutrophil activation [81] and delaying neutrophil apoptosis [82].

CF is clearly associated with a defect in ASL pH regulation. Defects in HCO3

- transporters other

than the CFTR can be envisioned, but require further investigation.

Transheterozygosity

After extensive genetic screening, 33–50% of patients with diffuse bronchiectasis are characterisedas heterozygous for the CFTR [66]. As the theoretical frequency of this heterozygosity in the

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general population is 3.3%, this highly elevated frequency suggests that heterozygosity for theCFTR may have pathogenic consequences. It may predispose to the development and severity of bronchiectasis by potentiating other genetic factors affecting airway physiology or add todeleterious environmental factors.

Further support for this hypothesis comes from evidence of an abnormal nasal electrophysio-logical phenotype in patients with bronchiectasis carrying one CFTR mutation, intermediate

between control subjects or patients with no CFTR mutations, on the one hand, and patients withtwo CFTR mutations on the other [66]. However, the absence of any increased prevalence of bronchiectasis in obligate heterozygotes [83], although they display abnormal Cl- transport [84],suggests that carrying a single CFTR mutation is not solely responsible for development of thedisease.

A total of 55 patients with diffuse idiopathic bronchiectasis were studied and an unexpectedly highproportion (5%) of heterozygosity was found for both CFTR and ENaC mutations [75]. As theexpected frequency of such transheterozygosity in the general population is 0.3%, the finding of sohigh a prevalence of mutations of both ion transporters suggests that it is clinically relevant. Slightdefects in both channels, which separately would not be sufficient to alter ASL homeostasis, are

likely to combine their deleterious effects and lead to deficient ENaC/CFTR interaction. Along thisline, we speculate that transheterozygosity of a single CFTR mutation and a mutation in anotherion channel might create the conditions for abnormal ASL hydration regulation and defectivemucociliary clearance.

Conclusion

It is likely that the true incidence of cases of ion-transport-related bronchiectasis among allbronchiectasis is underestimated, given the lack of specific symptoms. Although much is now known about the CFTR, the study of other channelopathies is only just beginning. Except for

typical CF and CFTR-related syndrome, it is difficult to demonstrate a causal relationship betweenbronchiectasis and ion transport defects. The continuum of ion transport dysfunction fromnormal to disease phenotype makes it difficult to define a clear-cut level for the involvement of iontransport defect in the physiopathology of bronchiectasis [85]. Therefore, in order to ascertain therole of channelopathies in the genesis of bronchiectasis, mutations in a given channel and therelated ion transport function should be systematically investigated in bronchiectatic patients.Such studies may point to interesting therapeutic pathways aimed at normalising the first cause of the pathogenic cascade resulting in bronchiectasis.

Statement of interestNone declared.

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Chapter 11

Bronchiectasis

associated with

inflammatory bowel

diseasePh. Camus* and T.V. Colby #

Summary

The two major inflammatory bowel diseases (IBD), ulcerativecolitis and Crohn’s disease (CD), can involve the respiratory system in several ways. The most typical pattern of involvementis in the form of airway inflammation and narrowing, which

may involve specific areas of the tracheobronchial tree from thetrachea to the bronchioles or which can be diffuse. Markedinflammation, which can be granulomatous in CD, causes, attimes, marked airway obstruction. This pattern of involvementis amenable to different forms of inhaled and oral corticosteroidtherapy. Drugs used to treat IBD are though to have noresponsibility in causing the syndrome. This is in contrast toparenchymal lung disease in IBD. Colectomy may trigger theonset of airway involvement and will not improve or cureestablished airway inflammation in IBD.

Keywords: Airway inflammation, bronchiectasis, bronchiolitisobliterans-organising pneumonia, granulomatous inflammation,inflammatory bowel disease

*Dept of Pulmonary Disease andIntensive Care, University MedicalCenter Le Bocage and MedicalSchool, Universite de Bourgogne,Dijon, France.#Dept of Pathology, Mayo Clinic,Scottsdale, AZ, USA.

Correspondence: Ph. Camus, Dept of Pulmonary Disease and IntensiveCare, University Medical Center LeBocage and Medical School,Universite de Bourgogne, POB77908- F-21079, Dijon, France, [email protected]


Patients with either of the two major inflammatory bowel diseases (IBD), ulcerative colitis(UC) and Crohn’s disease (CD), may develop a host of unusual, well-defined thoracic

manifestations (table 1) [1–6]. Among these manifestations, a distinctive pattern of airway

inflammation and scarring involving the major and minor airways (depending on the patient) hasemerged clinically, endoscopically and pathologically as a consistent and increasingly recognisedform of respiratory involvement in IBD. The severity ranges from the asymptomatic state tocopious and disabling bronchorrhea or acute asphyxia. In addition, IBD is also associated withinterstitial lung disease (ILD) with a variegated pattern on high-resolution computed tomography (HRCT), sterile necrobiotic neutrophilic nodules and pleuropericardial involvement. It isimportant to appreciate that therapy with several IBD-modifying drugs can also produce diffuse ILD,

1 6 3

P h

. C A M U S A N D T

. V . C O L B Y



T a b l e 1 . A i r w a y

i n v o l v e m e n t i n i n f l a m m a t o r y b o w e l d i s e a s e

F r e q u e n c y /

i n c i d e n c e

O n s e t

p o s t - c o l e c t o m y

U C

v e r s u s

C D

E v i d e n c e b a s e f o r

a s s o c i a t i o n w i t h

M a i n c o m p e t i n g d i a g n o s i s

D r u g s

I B D

A i r w a y i n f l a m m a

t i o n /

d e f o r m i t y / s c a r r i n g

+ + +

+ + +

U C . C D

N o

S t r o n g

G l o t t i s , l a r y n x , s

u b g l o t t i c r e g i o n

+

A N C A r e l a t e d ( g r a n u l o m a t o s i s w i t h

p o l y a n g i i t i s ( W e g e n e r ’ s

) ) , T B , s a r c o i d o s i s

T r a c h e a

+ +

H e r p e s v i r u s , p o l y c h o n d r i t i s , T B ,

m a l i g a n c y , p

a p i l l o m a

M a i n b r o n c h i

+ + +

C l a s s i c c h r o n i c b r o n c h i t i s / s

m o k i n g b r o n c h i e c t a s i s

S m a l l / p e r i p h e r a l a i r w a y s

#

+ +

O t h e r c a u s e s o f a c u t e / c

h r o n i c b r o n c h i o l i t i s

I n f i l t r a t i v e l u n g d

i s e a s e

+ +

U n k n o w n

U C , C D

D i f f u s e I L D

I L D d u e t o d r u g s / o t h e r c a u s e s ,

m e t a s t a t i c l y m p h a

n g i t i c s p r e a d

N S I P

+

S t r o n g

M o d e r a t

e

I L D d u e t o d r u g s / o t h e r c a u s e s

P u l m o n a r y i n f i l t r a t e s w i t h

e o s i n o p h i l i a

+ +

S t r o n g

L o w

P I E d u e t o d r u g s / o t h e r c a u s e s

B O O P

+ + +

U C . C D

M o d e r a t e

S t r o n g

B O O P o f o t h e r c a u s e s

I L D w i t h g r a n

u l o m a s

+ + +

C D . .

U C

W e a k

S t r o n g w i t h

C D

T B , s a r c o i d o s i s , H S P

D e s q u a m a t i v e i n t e r s t i t i a l

p n e u m o n i a

V e r y r a r e

U n k n o w n

U n k n o w n

L o c a l i s e d m a s s

o r m a s s e s a n d

n o d u l e s

M a l i g n a n c y

G r a n u l o m a t o u s i n f l a m m a t i o n

+

C D . .

U C

L o w

S t r o n g w i t h

C D

T B , s a r c o i d o s i s

L o c a l i s e d B O

O P

+ +

U C . C D

W e a k

M o d e r a t

e

N e c r o b i o t i c n

o d u l e s

"

U n c o m m o

n

U C . .

C D

N o

M o d e r a t

e

B a c t e r i a l i n

f e c t i o n

T h e r a p y - r e

l a t e d

l u n g d i s e a s e

D o e s n o t a p

p l y

D r u g - i n d u c e d p

n e u m o n i t i s

+ + +

D o e s n o t a p p l y

U C , C D

O p p o r t u n i s t i c i n

f e c t i o n s

+ +

D o e s n o t a p p l y

P l e u r a l s u r f a c e

+ +

+

U C , C D

W e a k

M o d e r a t

e

M a l i g n a n c y , i n f e c t i o

n , a u t o i m m u n e

S e r o s i t i s

+ +

E f f u s i o n

+ +

P e r i c a r d i a l s u r f a

c e

+ +

+

U C , C D

M o d e r a t e

M o d e r a t

e

M a l i g n a n c y , i n f e c t i o

n , a u t o i m m u n e

P e r i c a r d i t i s

+ +

P e r i c a r d i a l e f f u s

i o n o r t a m p o n a d e

+

1 6 4

I N F L A M M A T O R Y B O W E L D I S E A S E



involvement of the pleural space or cardiac hyper-sensitivity reactions. Several drugs used to treat IBD,such as anti-tumour necrosis factor (TNF)-a therapy,put patients at risk of developing opportunisticpulmonary infections, including pulmonary tubercu-losis and should be considered in the list of dif-ferential diagnoses.

This chapter will focus on airway inflammation inIBD which can occur in both UC and CD, withgreater incidence in the former. Although someoverlap exists, the inflammation associated with eachcondition has distinct clinical and pathologic features.Notably, granulomatous inflammation is observed inthe airways and/or lung parenchyma in CD, whilenon-granulomatous inflammation is seen in UC.

The evidence that IBD is causally associated with

airway inflammation is based on: 1) the steady flow of consistent clinical descriptions of an associationworldwide since the 1960s; 2) the common embryo-logic ancestry of the bronchi and bowel suggests co-involvement in the same disease process; 3) thefrequent reports of airway involvement occurringpost-colectomy in individuals with UC with nohistory of lung disease [1, 7]; 4) the impressiveresponse of airway inflammation to inhaled or oralcorticosteroid therapy at least in patients with mild

or moderate disease [1, 8–11]; and 5) epidemiologicstudies showing greater prevalence of bronchitis inIBD patients overall [12]. Taken together, thesefindings suggest a true causal association of IBDwith airway inflammation [12, 13].

In approximately 75% of IBD patients who developairway involvement, the onset of respiratory symp-toms is weeks to years after the development of clinically confirmed IBD. Post-colectomy patientsare not immune to the development of airway

involvement (which may be very severe) andcolectomy may even be a risk factor for onset andprogression of severe airway involvement in UC[1, 7]. Less often, IBD-related airway involvementpre-dates the onset of the IBD (raising difficultdiagnostic issues), develops concomitantly with theinaugural flare of the IBD, or parallels flare ups of theIBD [1, 6]. Contrasting with ILD (the other majorpattern of respiratory involvement in IBD), many IBD patients who develop airway involvement do so

at a time when they are no longer exposed to IBD-modifying drugs, either because the IBD is quiescentor because of their post-colectomy status.

Airway involvement in IBD is generally inflamma-tory in nature and therefore typically amenable totherapy with inhaled or oral corticosteroids, may

T a b l e

1 . C o n t i n u e d .

F r e q u e n c y /

i n c i d e n c e

O n s e t

p o s t - c o l e c t o m y

U C

v e r s u s

C D

E v i d e n c e b a s e f o r

a s s o c i a t i o n w i t h

M a i n c o m p e t i n g d i a g n o s i s

D r u g s

I B D

O t h e r t h o r a c i c m

a n i f e s t a t i o n s

+

–

V e n o u s / p u l m o n

a r y

t h r o m b o e m b o l i s m

+ +

U C , C D

N o

S t r o n g ; o d

d s

r a t i o , 3

F i s t u l a s

1

+

S t r o n g

L o w s e r u m

a l b u

m i n a n d

p u l m o n a r y o e

d e m a

V e r y r a r e a t p r e s e n t

U C : u l c e r a t i v e c o

l i t i s ; C D : C r o h n ’ s d i s e a s e ; I B D :

i n f l a m m a t o r y b o w e l d i s e a s e ; B O

O P : b r o n c h i o l i t i s o b l i t e r a n s - o r g a

n i s i n g p n e u m o n i a ; I L D : i n t e r s t i t i a l l u n g d i s e a s e ; N S I P :

n o n s p e c i f i c i n t e r s t i t i a l p n e u m o n i a ; A N C A : a n t i n e u t r o p h i l c y t o p l a s m i c a n t i b o d y ; T B : t u

b e r c u l o s i s ; P I E : p u l m o n a r y i n f i l t r a

t e s a n d e o s i n o p h i l i a ; H S P : h y p e r

s e n s i t i v i t y p n e u m o n i t i s .

– : n o / n e v e r ; + : u n

u s u a l ; + + : o c c a s i o n a l ; + + + : c o m m

o n a m o n g I B D - r e l a t e d r e s p i r a t o

r y m a n i f e s t a t i o n s ( o v e r a l l i n c i d e n c e i s l o w w i t h 1 7 7 i n s t a n c e s i n 1 5 5 p a t i e n t s i n 2 0 0 7 [ 6 ] ;

. : g r e a t e r , . . : f a r g r e a t e r ; , : l o w e r ; , : e q u a l t o .

# : . 7 t h g e n e r a t i o n ;

" : a l s o n a m e d p u l m o n a r y P y o d e r m a g a n g r e n

o s u m ;

1 : c o l o b r o n c h i a l o r o e s o t r a c h e a l .

1 6 5

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. V . C O L B Y



localise from the glottis to the smallest airways depending on patient and stage of the disease, may be localised or diffuse in the airways, or may lead to a reduction in airway patency which, wheninvolving the upper airway (in particular larynx, vocal cords or glottis), carries the risk of rapidly progressive life-threatening airway obstruction [1, 14, 15].

The diagnosis of any respiratory manifestation in IBD is one of exclusion and the main competingdiagnoses are listed in table 1. Differential diagnoses include other systemic conditions capable of

involving the central airways, such as sarcoidosis, relapsing polychondritis, tracheal amyloidosis orpapillomatosis, antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (granulomatosiswith polyangiitis (Wegener’s)), idiopathic subglottic stenosis, chronic bronchitis, bronchiectasis orsuppurative airway disease of other causes [16, 17]. One must also consider drug-induced disease,since the IBD-modifying drugs sulfasalazine and mesalazine can produce adverse reactions in thelung or heart [18]. Similarly, therapy with corticosteroid drugs and anti-TNF-antibody therapy increases the risk of developing opportunistic pulmonary infections including tuberculosis.Therefore, IBD patients who present with ILD, purulent necrobiotic nodules, acute bronchiolitis andgranulomatous airway inflammation need to be carefully investigated to exclude infection and druginduced changes [3, 19, 20].

Literature milestones

The first report on airways disease in UC by LOPEZ BOTET and R OSALEM ARCHER [21] described theessentials of a unique disease, subsequently identified in many patients in several studies. Theauthors reported the occurrence of aggressive ulcerous bronchitis and bronchiectasis (confirmedon contrast bronchography), associated with profuse bronchorrhoea and haempotysis, in a 38-

year-old female 10 years after colectomy for UC. Prednisolone treatment improved her symptomstemporarily before she developed refractory airways disease, amyloidosis and eventually died. Theauthors suggested that the two manifestations reflected one single disease, and that the

inflammatory process may have shifted to the airways.

In 1976, KRAFT et al . [22] drew attention to the potential association of IBD and disabling airway disease. In their seminal paper they described six adult IBD patients; five UC and one with regionalenteritis (CD). All of the patients were nonsmokers who developed chronic, otherwise unexplained,bronchorrhea 3–13 years after the onset of their IBD. In two patients, the airway disease developedfollowing total proctocolectomy. There was a correlation of bowel and respiratory symptoms in fourpatients. Five patients had an obstructive pattern of pulmonary dysfunction. Bronchiectasis wasevidenced using contrast bronchography in four patients. Oral corticosteroid therapy used to treatthe underlying IBD was not reported to notably influence the course of airway involvement.

HIGENBOTTAM et al. [8] described 10 nonsmoking patients with UC who presented with a chronicproductive cough, which was not felt to be due to sulfasalazine treatment. Bronchial epithelialbiopsies from four patients revealed basal reserve cell hyperplasia, basement membrane thickeningand submucosal inflammation. Treatment with inhaled corticosteroid (beclomethasone diproprio-nate) relieved the cough in seven patients. These investigators highlighted the possibility that airway involvement in UC might be explained by the common embryologic ancestry of the bronchial andintestinal epithelium, representing a new extra-intestinal manifestation (EIM) of the disease.

These observations were expanded in a study by CAMUS et al. [1] of 33 IBD patients (UC n527,CD n56) of whom 20 presented with airway involvement. Three out of these 20 patientspresented with severe upper airway inflammation narrowing and tortuosity, 15 with central airway inflammation or suppurative airways disease (trachea or major bronchi), of whom six haddocumented bronchiectasis, and two with small airway involvement or bronchiolitis. In the threepatients with central airway involvement and upper airway obstruction, airway endoscopy showedfriable, velvety airway inflammation with cobble stoning and haemorrhage. Airway patency wasreduced to 20% of normal in one case and appearance of the mucosa in the airway wasreminiscent of that in the colon. In the 15 patients who presented with large airway inflammation,

1 6 6




airway endoscopy also showed severe inflammation with glittering erythema and oedema severely narrowing the airway lumen with effacement of bronchial cartilaginous rings. The bronchoalveolarlavage (BAL) showed increased neutrophil counts, which diminished in responders oncecorticosteroid therapy was administered in parallel with the resolution of the airways symptoms of cough and sputum. Pulmonary function (notably forced expiratory volume in 1 second) alsoimproved dramatically by o50%, even in patients with bronchiectasis. Six further patientspresented with febrile pulmonary infiltrates corresponding pathologically to bronchiolitis

obliterans-organising pneumonia (BOOP), a disease of the transitional zone of the lung that istraditionally considered an ILD. However in IBD, BOOP was notable for prominent ulcerative orsuppurative involvement of the distal bronchioles, raising the question of the dominant site of involvement in IBD-related BOOP. Inhaled corticosteroids were effective in controlling thesymptoms of cough, sputum and airway pathology in those patients with chronic bronchitis (in,60%), but were less efficacious in doing so in patients with bronchial suppuration,bronchiectasis or chronic bronchiolitis (,30%) in whom oral corticosteroid were effective. Aliterature review indicated that upper airway involvement accounted for 11.1% of the reportedcases, large and small airway involvement 83.3% and 5.6%, respectively, and that about half thecases of IBD-associated airway involvement had developed post-coletomy.

GARG et al . [23] described the HRCT features of airway inflammation in seven patients with UC(five post-colectomy) who presented with cough and recurrent respiratory infections. Fibreopticbronchoscopy in six patients showed diffuse mucosal erythema and oedema that were most severein the proximal airways. Sinus imaging showed mucosal thickening in six patients, a feature thathas not been described previously. HRCT features included bronchiectasis in six patients,peripheral airway involvement in four patients and a rigid and stenotic trachea in three patients.

CASEY et al. [24] reviewed their experience with 11 lung biopsies from CD patients who presentedwith diffuse or localised pulmonary opacities. Workup for an infection was negative in all 11 cases.The major pathologic features in four patients were chronic bronchiolitis with non-necrotising,

non-coalescent granulomatous bronchocentric inflammation. Two further patients had acutebronchiolitis associated with a neutrophil-rich bronchopneumonia with suppuration and vaguegranulomatous features resembling that seen in UC. The remaining five patents were diagnosedwith ILD or organising pneumonia.

In 2007, BLACK et al . [6] reviewed the literature on 171 instances of respiratory pathology (99 withairway involvement) in 155 IBD patients. Large airway involvement was found to be the mostcommon pattern of involvement, accounting for 67% of the cases overall, with bronchiectasisbeing the most frequently reported pattern. Involvement of the upper airway (glottis and larynx)and small airway accounted for 15% and 17% of the cases, respectively.

Several other notable papers have consistently described similar, if not identical, cases and/orreviewed earlier literature. Taken together, these studies further confirm a true association of IBDand large or small airway involvement, and the beneficial effect of corticosteroid therapy in many cases [3, 9, 11, 20, 25–30].

Epidemiology: risk factors

Clinically apparent airway involvement is uncommon in IBD. KRAFT et al . [22] calculated aprevalence rate of 0.21% in their IBD clinic. In a recent study of 165 patients with bronchiectasisdetected on computed tomography scans, an underlying cause was identified in 122 (74%)

patients; five patients had a history of IBD (up to 10 years earlier in one case), two were post-colectomy and in one patient the diagnosis was made during a flare up of IBD [17].

Figures for prevalence may be higher if subclinical airway involvement is defined by subnormalpulmonary physiology (a common occurrence in IBD, particularly during flare ups) [31–34],increased exhaled nitric oxide [35], minimal changes of uncertain significance on imaging [36] orchanges in induced sputum cytology [35, 37, 38]. However, although subclinical changes in BAL

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cell profile have been found in IBD [35, 39], there is no current evidence to suggest a link betweenthese subtle changes and the likelihood of developing overt airway or parenchymal lunginvolvement at a later time. Females outnumber males with an approximate ratio of 1.8–2.1 [1, 6].Colectomy has been suspected to be a risk factor for the development of IBD (mainly UC)-relatedairway involvement [1, 8, 22]. Recently, KELLY et al. [7] confirmed this in 10 patients with IBD(CD n55) and bronchiectasis. Eight of these patients had developed respiratory symptoms fromwithin a few weeks to decades after colectomy. One may question whether IBD-associated airway

involvement is linked to colectomy per se , or occurs as a result of IBD-modifying drug withdrawalpost-colectomy. However, the long time delay of several decades in some patients tends to supportthe notion that airway involvement in IBD is an EIM of the disease, rather than a complication of drugs or a result of drug withdrawal. Furthermore, colectomy in patients with IBD and airway involvement may lead to deterioration of the respiratory condition and should not be proposed inan attempt to cure the airway involvement [1]. A high rate (52%) of EIM other than in the lungwas noted in IBD patients with airway involvement. Smoking is unlikely to play a causal role asmost patients with the association are nonsmokers or reformed smokers [1, 40].

Clinical presentationsUpper airway obstruction: glottic and subglottic

This presentation is unusual and it is the most worrisome pattern of involvement in IBD as this may cause rapidly progressive, severe airway compromise and acute asphyxia. IBD-related upper airway obstruction has been described in both UC and CD, often in association with active IBD, having asimilar clinical presentation in both conditions (figs. 1 and 2). Early onset of symptoms of sorethroat and hoarseness can be mistaken as upper respiratory tract infection [1, 6, 14, 15]. Theseannunciating symptoms may not receive appropriate attention. Following this a continuousresonant deep-toned barking cough may develop, sometimes with hoarseness due to vocal cord

oedema or dysmotility, stridor and blood-tinged sputum [1, 14, 41, 42]. The overall amount of sputum is usually insignificant, except if patients have associated tracheal or large airway involvement, which is frequent. In a few patients, flow reduction [43] is noted on the inspiratory andexpiratory limb of the flow–volume loop [26], indicating fixed as opposed to variable airway obstruction. Inexplicably, upper airway inflammation can accelerate and progress rapidly, producingsevere airway compromise within a few hours or days [1, 6, 14, 15, 28], at times requiring mechanicalventilation [15]. Unequivocal airway stenosis can be visualised on computed tomography [44, 45].On endoscopy, there is marked erythema of the vocal cords, glottis or subglottic region with oedema,a velvety friable oedematous mucosal swelling, whitish or reddish nodules, distorted anatomy andpus. In some cases, the 5-mm fibreoptic bronchoscope could not be passed through and beyond the

stenotic area without causing further compromise [1, 14], or progression of the scope in the trachearequired repeat bending to reach the more distal trachea [1]. Macroscopically, appearance of theairway walls is reminiscent of that in the colon in UC [25, 40]. Beyond the stenotic area, there ismarked inflammation and bulging of tracheal walls. The extent of involvement varies depending onthe patient, being limited to the upper trachea in some and in others extending upstream beyond thetracheal bifurcation to involve the main stem bronchi, also in the form of diffuse inflammation orerythematous or haemorrhagic nodular deformity, distorting and reducing airway patency [25].Imaging studies using HRCT planar reconstruction or magnetic resonance imaging demonstratemarked thickening of the airway wall and a correlative reduction in airway calibre [1, 43, 45, 46].Pathologically, bulging of the airway wall corresponds to dense lymphoplasmacytic and oedematous

mucosal infiltrate with, sometimes, lymphocytes, neutrophils or rare eosinophils permeating themucosa up to the epithelium which is also infiltrated (fig. 2a and b). The overlying airway mucosamay show squamous metaplasia or may be ulcerated [1, 47]. When present, noncaseatinggranulomas suggest a diagnosis of CD as opposed to UC.

The pattern of upper airway obstruction in UC requires expeditious and emergent management torestore airway patency via interventional endoscopy using debridement, laser, argon plasma

1 6 8




coagulation, electrocautery, dilation, stent placement (if the lesion does not occupy the glottic andsubglottic space and does not involve the vocal cords) and topical injections of corticosteroids and/or mitomycin C [28, 45, 46]. Inhaled, nebulised and parenteral corticosteroids and infliximab havealso been used and this has met with success in a few cases [45]. Breathing a helium–oxygen mixture(heliox) is indicated during the acute phase of the disease. Prudent dilatation of the airway usingcalibrated bougies can be considered to restore airway patency. However, this was complicated by mediastinitis in one case [43]. Overall, the response to combined treatment is encouraging.

Central airway involvement: trachea and main stem bronchiThis is the most common and most disabling pattern of airway involvement in IBD with 67 casesreported overall (figs. 1 and 2) [1, 6, 22, 23, 40, 47–52]. Age at onset of the airway disorder is, onaverage, 43 years. Two-thirds of the patients were females [6]. Three main patterns were described:1) chronic bronchitis with cough and moderate sputum, 2) suppurative airway disease withabundant bronchorrhea, and 3) chronic bronchiectasis [1, 6]. It is unclear whether there is a

b)a) c)

e)d)

h)g)

f)

Figure 1. Chest and endocopic imaging in inflammatory bowel disease-related airway involvement. Upper

airway inflammation and stenosis is best evidenced using a) computed tomography (CT) reconstruction ormagnetic resonance imaging and b) fibreoptic bronchoscopy. Inflammation may localise in the glottic or

subglottic area, often involving the trachea (b) and proximal airways which show b) cobble stoning and c)

inflammation and pus. d) Radiographically, minimal changes are present in early disease in the form of bibasilarbronchial tramlines. On CT examination there is a combination of e) airway wall thickening, f) glove-finger

shadows reflecting airway filling by inspissated secretions or g) a tree-in-bud appearance reflecting small airway

inflammation. h) Late changes are in the form of bronchiectasis. Often changes on endoscopy and imaging will

improve with inhaled alone or inhaled and oral corticosteroid therapy.

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continuum from chronic bronchitis to suppurative airways disease or bronchiectasis in a givenpatient. However, the clinical impression is that some patients do progress from simple chronic

bronchitis to bronchiectasis in the absence of, and sometimes in spite of, corticosteroid therapy fora few months or years. Cough and sputum are typically unexplained other than by the backgroundhistory of IBD. The condition essentially occurs in adulthood in nonsmoking IBD individuals withno history of lung of airway disease. Typically, IBD-related large airway disease manifests with theinsidious or rapid development of cough productive of variable amounts of clear, purulent orblood-stained sputum. Copious bronchorrhea (.100 mL and o500 mL) has been reported in afew cases [1, 53]. Some patients experienced parallel flare ups of bowel and bronchial symptoms,further reinforcing the notion of a true association [1, 8, 49]. In several instances abundantbronchorrhea and severe airway involvement developed a few days to a few weeks after totalcolectomy as though aggressive inflammation had ‘‘shifted’’ away from the bowel to the airways

[7, 48, 51]; although inexplicably, airway involvement can occur much later [1, 7, 21].

Pulmonary function testing usually reveals a moderate-to-severe obstructive or mixed obstructiveand restrictive spirometric profile [1]. There is little change in airflow upon inhalation of abronchodilator drug. Bronchial responsiveness to methacholine is usually normal [1], and thiscontrasts with the background of pronounced inflammation noted on pathology. The figures oftenimprove dramatically following inhaled and/or oral corticosteroid therapy [1, 11].

a) b) c)

d)

g)

e) f)

Figure 2. Airway pathology in inflammatory bowel disease (IBD)-related airway involvement. a, b)

Tracheobronchial inflammation is in the form of a dense and florid mixed submucosal lymphoplasmacyticinfiltrate within the airway wall, sometimes markedly reducing airway patency. The mucosa can be ulcerated (a)

and the inflammatory infiltrate (including neutrophils and a few eosinophils) can be seen permeating and homingtoward the airway mucosa (b). Bronchial glands may be damaged or destroyed (not shown). Inflammation mayalso involve c) the more distal airways or bronchioles (diameter of the airway lumen ,1.8 x 1 mm) down to d) the

smallest airways (showing at least six bronchioles involved) in the form of acute and chronic exquisitely broncho-

or bronchiolocentric inflammation, while the vasculature is spared and uninvolved. Occasionally, there is e)purulent bronchiolitis (can also be seen in IBD-associated bronchiolitis obliterans-organising pneumonia) and/or

f) purulent bronchiolar and tissue necrosis. g) In a few cases constrictive bronchiolitis and chronic obstruction to

airflow develop as a late manifestation.

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Although the extent of abnormalities on imaging is generally in proportion to the severity of clinical symptoms, abnormalities on the chest radiograph can be surprisingly small and discreet,being simply in the form of linear basilar opacities or the ‘‘dirty lung’’, despite disabling cough andabundant sputum. Radiographically, early or mild cases show minimal or no changes. Moreadvanced or progressive cases show bibasilar tramlines indicating bronchial wall thickening,especially in cases with suppurative airway disease. Tubular or cystic bronchiectases are seen in yetmore advanced cases [52]. On HRCT examination, early cases may evidence non-uniform lung

emptying on full expiration thought to reflect peripheral airway obstruction [36, 52]. In moreadvanced cases, thin-cut sections of airway on HRCT [54] show airway wall thickening [11] andan increased external diameter of the airway compared to the adjoining vessel. In more severecases, extensive bronchial wall thickening and basilar or widespread dense-tubulated ordichotomously-branched opacities, which are also known as glove-finger shadows, are seen[1, 53]. The latter changes are reminiscent, if not similar to, those in allergic bronchopulmonary aspergillosis and may represent impaction of inspissated mucoid or purulent secretions filling theairway lumen. However, more advanced cases show basilar or more widespread cysticbronchiectasis in addition to the aforementioned changes [1, 53, 55–58]. Subtle changes can bepresent in distal regions of the lung in the form of small irregular dichotomously branched

shadows, the so-called tree-in-bud appearance, more often than not [58] subpleurally in thebibasilar lung [53]. These changes are thought to represent peribronchiolar cellular cuffing andmay correlate pathologically with acute, subacute and/or chronic bronchiolitis [3, 20, 59]. HRCTimaging of maxillary and ethmoid sinuses may demonstrate mucosal thickening in up to 60% of patients with UC-related large airway involvement [23].

Findings on endoscopy may be near normal in patients with early or mild symptoms such ascough, or may show diffuse erythema. Bronchial biopsy specimens at this stage may evidencesubmucosal inflammation [1, 3]. Neutrophils are increased in the BAL [1] and on follow-up thesecells diminish in number and percentage in patients who respond to inhaled corticosteroids in

terms of improvement in cough and sputum [1]. In general, in patients with IBD-related airway involvement, changes are evident endoscopically [1, 9, 23] in the form of erythema, oedema,velvety bulging of the tracheal or bronchial walls and whitish or reddish cobble stoning [46, 47].The changes may be predominant in the trachea or they may extend in the form of sparklingoedema in main stem bronchi and more distally. At times, reduced airway patency prevents fullinspection of the bronchial tree [1, 60]. Pathologically, the underlying IBD seems to repeat theabnormalities found in the bowel [1, 3]. A dense submucosal collection of plasma cells andlymphocytes deeply infiltrates the airway wall [1, 3, 11]. The epithelium undergoes squamousmetaplasia and/or is ulcerated. Neutrophils and rare eosinophils may be interspersed in thecellular infiltrate and epithelium. Subepithelial airway glands beneath the mucosa may be

destroyed by the infiltrate and inflammatory cells may extend around the ducts of the bronchialglands and into the glands themselves[1]. IBD-related bronchiectasis differsclinically and pathologically from typicalbronchiectasis. The former is positively influenced by corticosteroid therapy and,pathologically, the latter shows a lessdense and conspicuous cellular infiltrateand with more germinal centres (follicu-lar bronchiectasis). The inflammatory infiltrate in IBD-related airway involve-ment may extend to more distal airwayswhich, if available for examination, forexample on a lung resection specimen [1, 3],show a similar pattern of inflammationand stenosis down to the bronchioles(fig. 2c) [1, 57]. There is histological

Table 2. Airway involvement in inflammatory bowel disease

Site of involvement

Larynx/glottis/subglottic area 2 (2.2) Tracheal¡subglottic inflammation/stenosis 15 (16.6)

Bronchiectasis 44 (48.9)

Chronic bronchitis 13 (14.4)Suppurative airways disease 5 (5.6)

Bronchiolitis/granulomatous bronchiolitis 10 (11.1)

Diffuse panbronchiolitis 1 (1.1)

Pure constrictive bronchiolitis 2 (2.2)ILD with a bronchiolitis component

such as BOOP

21

Data are presented as n (%) or n. ILD: interstitial lungdisease; BOOP: bronchiolitis obliterans-organising pneu-

monia. Data from [6].

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similarity between the airways and colonic mucosa in UC-related large airway involvement,particularly with regards neutrophilic infiltration, mucosal ulceration and dense underlyingchronic inflammation with plasma cells [3].

There is little correlation between the degree of airway inflammation seen on endoscopy and theamount of expectorated sputum. Stains and cultures yield inconsistent results, being sterile orshowing normal flora, with rare Pseudomonas colonisation. Symptoms inconsistently improvefollowing a course of antibiotics except if used in conjunction with inhaled or oral corticosteroids(see later section). In patients who respond to corticosteroid therapy, the airway appearances canreturn to normal [30]. In a few patients, however, late changes will develop in the form of trachealstricture or deformity, cicatricial obliteration of one or more bronchial orifices or localised web-like strictures.

Small airway involvement: bronchiolitisThere is some confusion surrounding the term ‘bronchiolitis’, according to whether the condition issuspected clinically using HRCT, pulmonary function testing or BAL, or is diagnosed pathologically using transbronchial sampling or surgical biopsies (the latter is rarely indicated). Bronchiolitis is bestdefined pathologically by inflammatory events centred on small noncartilagenous airways generally measuring ,2 mm (approximately the 7th generation). These airways are situated in the centralportion of the secondary pulmonary lobule and, when inflamed, result in centrilobular nodulesvisible on HRCT. Bronchiolitis may be the predominant finding on a lung biopsy specimen(although it may simply reflect or accompany inflammatory changes in proximal bronchi inbronchiectasis) and/or may extend and transition into more distal alveolar lung in the form of BOOP. Evaluation of bronchiolitis requires careful exclusion of an infectious aetiology.

Small airway involvement in IBD has been reported in 17 patients overall [6]. The conditionoccurs at a younger age (29 years on average) and in both sexes equally, compared to large airway involvement [6]. In approximately a third of the patients, bronchiolits pre-dated the onset of theIBD [6]. Cough and sputum are not always present and the condition may manifest with cough,dyspnoea, or wheeze accompanied by obstructive or restrictive lung function abnormalities [1, 43, 61].Radiographically, the chest film can be normal or demonstrate small diffuse irregular or nodularopacities [24, 62, 63].

Although bronchiolitis can be the predominant histopathologic finding in both UC and CD [1, 3,6, 19, 24, 43, 62–65], the pathological features differ between these conditions. In CD, there isassociated non-caseating, non-coalescent bronchiolocentric granulomatous inflammation [24, 66]while in UC, there is dense bronchiolocentric neutrophilic inflammation of the airway wall orsuppurative bronchiolitis with neutrophils filling the lumen. Although inflammation has apredilection to involve the bronchioles, inflammation of the neighbouring lung can be present,producing some parenchymal shadowing or consolidation on imaging [62], or focal suppuration

Table 3. Airway involvement in inflammatory bowel disease (IBD): evidence of relationship

High prevalence of co-existing extra-intestinal manifestations including sclerosing cholangitis

Absence of a history of airway or lung disease in childhood or adulthood

Low incidence of smokingNo other cause identified at the origin of the airway inflammation or bronchiectasis, no immune deficiency

Onset of airway involvement following the onset of the IBD

Parallel flares of airway and bowel manifestations (rare)

Onset of airway involvement after (sometimes very shortly or up to several years) proctocolectomyColectomy tends to aggravate symptoms and extent of involvement in the airways

Distinctive pathologic features or airway (trachea to the smallest airways) involvement

Similar macroscopic appearance and microscopic features of airway and interstinal inflammationMarked improvement with corticosteroid therapy, unlike classic airways diseases except asthma

Relapse of airway symptoms and inflammation with corticosteroid withdrawal

Similar embryologic ancestry of airways and bowel

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resembling Pyoderma gangrenoum in the skin [19]. Some cases show florid organising pneumonia(BOOP) in addition to acute bronchiolitis [1, 67]. A few cases exhibited a pattern identical to diffusepanbronchiolitis [1], as originally described in Japanese individuals [68], with interstitial foam cellsin addition to acute and chronic bronchiolitis [1, 3]. Scarring may follow acute and chronicbronchiolitis in the form of constrictive bronchiolitis characterised by severe obstruction to airflow (fig. 2g) [43]. In such patients, lung transplantation may be an option. The link between UC or CDand small airways involvement is more than tenuous and acute or chronic bronchiolitis should be

considered as part of the spectrum of UC-related airway involvement. Some investigators havecompared bronchiolitis, as it occurs in UC, to sclerosing cholangitis, another UC-associated EIM.

Management

There is sparse and limited evidence to indicate classic IBD-modifying drugs specifically inpatients with IBD-related airway involvement as these agents are largely ineffective. Althoughanecdotal reports described improvement of airway pathology after infliximab [45], IBD-modifying drugs are not recommended as a first-line treatment in this condition. Similarly, noresponse has followed therapy with azathioprine or cyclophosphamide.

Colectomy has not shown to be of benefit in the management of IBD-associated airways disease,and bowel surgery should be critically discussed in such patients. Furthermore, a number of instances have described the sudden onset, or clear deterioration, of IBD-associated airway involvement shortly after colectomy.

Corticosteroid drugs are the mainstay of treatment of IBD-related airway involvement. The routeof administration, dosage, titration and duration of treatment with corticosteroid varies with thepatient and is largely empirical.

In patients with airway involvement of moderate severity, such as mild chronic bronchitis, inhaled

corticosteroids are the treatment of choice. It is customary to start with a high dosage (2,000–2,500 mg?day -1) [1, 60]. Adjunctive oral corticosteroid therapy may be used but does not seem tobe an absolute requirement in early/mild disease. Inhaled corticosteroid therapy often providesconvincing improvement and excellent clinical control of the airway disease at this stage.Improvements in pulmonary function (if decreased prior to onset of treatment), imaging,endoscopy and BAL neutrophilia accompany the clinical improvement [1, 11, 30, 46]. Once asatisfactory response to treatment is obtained, inhaled corticosteroids can be slowly tapered every month or so to lower dosages similar to those used to treat asthma (1,200–1,600 mg?day -1). Patienteducation will permit any recrudescence in symptoms to be self managed by an increased dose of inhaled corticosteroids. The addition of oral corticosteroids (e.g. 25–60 mg oral prednisolone or

equivalent depending on sex, weight and severity) is normally indicated when there has been no orvery slow clinical improvement after a few weeks of inhaled corticosteroid therapy. Oral steroidsare more readily efficacious [40] enabling quicker control of symptoms and are indicated inpatients with moderate or severe airway involvement. It seems important to reach the normalclinical state as quickly as possible to ensure the best possible quality of remission. Oralcorticosteroids are tapered in a few weeks to the minimal effective dosage and withdrawn if possible. Short (2–6 weeks) bursts of oral corticosteroid may be indicated during relapses, shouldinhaled corticosteroids not suffice in controlling the disease.

Importantly, patients with more advanced or aggressive IBD-related large airway involvement, withor without bronchiectasis, may also benefit from long-term inhaled corticosteroid therapy. Imagingor pathology cannot readily identify which patient will respond to corticosteroid therapy [1], andclinical response may be associated with no change on imaging and little change in physiology [55–56, 69]. Cases with copious bronchorrhea are less likely to improve on inhaled corticosteroids,possibly due to altered pharmacokinetics of ICS in the diseased bronchial tree [1]. In such patients anebulised corticosteroid is indicated (e.g. 1 mg budesonide b.i.d . to q.i.d.), in addition to moreclassic oral and inhaled corticosteroids until improvement in symptoms occurs [1].

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Dosage and duration of treatment with oral and inhaled steroids are guided by clinical response,pulmonary function, bronchoscopy and follow-up HRCT (weighing up the risk of increasedradiation exposure particularly in young people). Although there is no evidence favouring this, weadvise patients to: 1) take their drugs accurately, avoiding any drug holiday even though they may feel better; 2) exercise regularly with the hope that inspissated secretions dislodge, enabling inhaledcorticosteroids to reach deeper, more distal airways and with the hope of minimising themusculoskeletal adverse effects of corticosteroids regardless of the route of administration; and

3) receive regular chest physiotherapy unless they reach the asymptomatic state. Fine-tuning of allaspects of steroid treatment in IBD-related airways disease is best carried out in close co-operationwith the patient, who is often a very astute observer of his/her own illness. It is interesting thatpaying attention to such small details such as careful explanation of how treatment works, andpunctuality in terms of inhalation and exercise often meet with improved compliance andsignificant clinical improvement, while the nominal dosage of corticosteroids was left unaltered.

Additional treatment options include courses of antibiotics since bouts of infection may repeatedly complicate the course of the airways disease, and expectorate actively by positional and voluntary coughing to clear the airways. There is no published or presented experience with azithromycin in

IBD-associated airway involvement. Given the benefit of this drug in other forms of inflammatory airways disease, an empirical therapy may be worth trying in selected patients [70].

Two issues are currently unresolved. 1) Although corticosteroid therapy is indicated, the specificeffect of inhaled, nebulised, systemic or topical corticosteroids in IBD-related upper airway involvement is unclear and difficult to evaluate separately. 2) Management of patients who presentwith aggressive airway inflammation and stenosis immediately or later during the course of theirdisease are a real concern. Corticosteroids may have transient or not perceptible effects and few options are left available, in as much as patients may suffer adverse effects of prolongedcorticosteroid therapy. We attempted to deliver higher steroid dosages topically via bronchialinstillations of methylprednisolone in saline via the fibrescope three times per week. A typical

40–80 mg dose in normal saline is instilled alternatively in the right and left bronchial tree every 2–3 days. Responders show a decrease in symptoms and some bleaching in the airways consistentwith reduced inflammation. The time interval between two instillations can be expanded to5–6 days in those who respond. Still, some patients’ illness is refractory to any form of therapy,with bronchial inflammation progressing to uncontrollable destruction of the entire tracheo-bronchial tree, pulmonary function deteriorating and adverse effects of corticosteroid therapy tragically increasing with time. Lung transplantation and novel techniques of airway managementneed to be discussed in such desperate cases [71, 72].

Statement of interestNone declared.

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71. Fabre D, Singhal S, De Montpreville V, et al. Composite cervical skin and cartilage flap provides a novel large

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Chapter 12

Immunodeficiencies

associated with

bronchiectasis J.S. Brown*, H. Baxendale #," and R.A. Floto ",+

Summary Bacterial infection of the lung is a cause of bronchiectasis andalso the main clinical problem in patients with bronchiectasis.As a consequence, inherited or acquired immunodeficienciesthat allow repetitive lung infection with respiratory patho-gens (such as Streptococcus pneumoniae and Haemophilusinfluenzae ) can drive the development and progression of bron-chiectasis. The immune defects most strongly associated with

bronchiectasis are those resulting in hypogammaglobulinaemia.These include the primary immunodeficiencies, common variable immunodeficiency and X-linked agammaglobulinaemiaand the secondary immunodeficiences caused by lymphopro-liferative malignancy, allogeneic bone marrow transplantationand chemo/immunotherapy. Identifying hypogammaglobulin-aemia is important and allows patients to be given immunoglo-bulin replacement, reducing exacerbation frequency andprobably progression of bronchiectasis. Conditions resulting in T-cell dysfunction (such as chronic HIV infection orimmunosuppression), reduced bacterial opsonisation (such ascomplement deficiencies), failure of phagocyte migration(leukocyte adhesion deficiency) and impaired intracellularkilling of bacteria (chronic granulomatous disease) may alsopredispose to bronchiectasis. In this chapter we describe themain immunodeficiencies associated with bronchiectasis andsuggest a staged approach to immunological investigations.

Keywords: Antibody, bronchiectasis, haematopoietic stem cell

transplant, HIV, immunodeficiency, T-helper cell type 17

*Centre for Respiratory Research,Dept of Medicine, Rayne Institute,Royal Free and University CollegeMedical School,#Division of Infection and Immunity,Dept of Immunology, Royal Free andUniversity College Medical School,London,"Cambridge Centre for LungInfection, Papworth Hospital, and+Cambridge Institute for MedicalResearch, University of Cambridge,Cambridge, UK.

Correspondence: J.S. Brown, Centrefor Respiratory Research, Dept of Medicine, Rayne Institute, Royal Freeand University College MedicalSchool, 5 University Street, LondonWC1E 6JF, UK, Email [email protected]

Eur Respir Mon 2011. 52, 178–191.Printed in UK – all rights reserved.Copyright ERS 2011.European Respiratory Monograph;

ISSN: 1025-448x.DOI: 10.1183/1025448x.10004210

B ronchiectasis is characterised by damage and dilatation of the bronchi allowing chroniccolonisation with significant numbers of bacterial pathogens. The initial damage to the bronchi

can be caused by infection. It is therefore not surprising that a range of immunodeficiencespredisposing to recurrent respiratory tract infections can lead to the development of bronchiectasis.

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Immunodeficiencies are defined as primary immunodeficiencies (PIDs), resulting from deleteriousgenetic mutations, or secondary immunodeficiencies (SIDs), where acquired insults have com-promised immune function. The pathogens usually associated with milder bronchiectasis includeStreptococcus pneumoniae and Haemophilus influenzae . Both are common nasopharyngeal com-mensals in adults and children that also cause acute bronchitis and pneumonia. It is probable thatimpaired host immunity to these pathogens initiates the development of bronchiectasis, which thenfurther compromises mucosal defences permitting infection and sometimes colonisation with

environmental bacteria, such as Pseudomonas aeruginosa .

Existing data on the causes of bronchiectasis is derived from relatively low numbers of patients,usually from specialist centres, who have been immunologically investigated to a variable extent asdiscussed by BILTON and JONES [1] in the first chapter of this Monograph. As a consequence, the trueproportion of bronchiectasis patients with a definable immunodefiency is unclear (and will certainly increase with modern molecular diagnostic approaches). From published reports, up to 7% of adultsand up to a third of children presenting with bronchiectasis will have a PID [2–6]. Reported rates of SID are lower but are likely to increase in line with more frequent use of immunotherapy, solid organand bone marrow transplantation and improved survival from HIV. In this chapter we will discuss

each of the major PIDs and SIDs that have been associated with bronchiectasis (table 1), beforedrawing some more general conclusions about mucosal immunity to bacterial infection.

Primary immunodeficiencies

Antibody deficiency syndromes

In most case series the commonest immune disorders associated with bronchiectasis are antibody deficiencies [2–7]. Antibody deficiency can be inherited or acquired and can be caused by a rangeof specific defects in antibody production, leading to several distinct immunological phenotypes

the most important of which are discussed below. S. pneumoniae and H. influenzae are bothsurrounded by an antigenic polysaccharide capsule which is a major virulence determinant forinvasive infection. The close association of antibody deficiencies as causes of bronchiectasisperhaps indicates that antibody-mediated immunity is a non-redundant mechanism for airwaysimmunity to these pathogens. Since antibody deficiency syndromes are responsible for significantnumbers of patients with bronchiectasis [3, 5, 6] and require specific management strategiesincluding antibody replacement, it is important that patients presenting with bronchiectasisshould be appropriately investigated for these conditions by measuring total serum antibody levels, specific antibody titres and antibody responses to vaccination.

Failure of any of the steps involved in antibody production can potentially lead to defec-tive humoral immunity. Gene mutations affecting early pre-B-cell development (such asrecombination-activating gene) will usually also impair T-cell production and lead to severecombined immunodeficiencies which almost always present in childhood. In contrast, adults may present de novo (although with a long history) with a block in pre-B-cell to immature B-celldevelopment giving rise to: X-linked agammaglobulinaemia (XLA) (usually caused by mutationsin Bruton’s tyrosine kinase (Btk )); defects in class switch recombination and/or somatichypermutation (which are necessary to generate high-affinity immunoglobulin (Ig)G, IgA andIgE) resulting in hyper IgM syndromes; and defects (which are currently only partially characterised) in generating functional antibody responses leading to common variableimmunodeficiency (CVID), IgA or IgM deficiency, IgG subclass deficiency and isolated specificantibody deficiency. The most common of these conditions are discussed below.

Common variable immunodeficiency

CVID is the most common adult primary immunodeficiency, with an estimated prevalence of 1 in25,000 in Caucasians [8]. Although many patients with CVID develop bronchiectasis, CVID is

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J . S . B R O W N E T A L .



relatively rarely identified as the cause of bronchiectasis in most published data for adult patients,varying from 0.7% to 2.4% of cases [3, 4, 6], and in 2–10% of childhood cases [2, 5].

CVID is characterised by reduced circulating Ig concentrations of one or more isotypes, with IgGlevels two standard deviations below normal [9] and poor responses to immunisation. The meanage at diagnosis has two peaks of around 30 years and in younger children [10, 11]. Adult patientswith CVID have often had symptoms for many years before diagnosis [11]. Familial CVID

Table 1. Primary and secondary immunodeficiencies associated with bronchiectasis

Type of

immunodeficiency

Mechanism of

immune defect(s)

Patients with

bronchiectasis

Bronchiectasis attributable

to this immunodeficiency

Primary

X-linkedagammaglobulinaemia#

Mutation in Bruton’s tyrosinekinase

f32% ,3% children,very rare in adults

CVID# 85% unknown 37% 2–10% children,

0.7–2.4% adults10–15% mutations in TACI,

CD28, ICOS

IgG subclass

deficiency"Unknown Unknown Children unknown,

4–48% adultsIgA deficiency" Unknown Unknown Children unknown,

2% adults

Specific antibodydeficiency"

Poor antibody response topolysaccharide antigens

Unknown Children unknown,4–11% adults?

Hyper IgE syndrome Mutations STAT3 Unknown ,2.5% children,

very rare adultsPhagocyte defects Varied Unusual ,1–10% children,

,1% adults

TAP deficiency TAP1 or TAP2 mutations Most patients Rare in children,very rare in adults

Secondary

CLL" Antibody deficiency Unknown Rare

Multiple myeloma" Antibody deficiency Unknown RareOther haematological

malignancy

Unknown Unknown Rare

HSCT " Associated with bronchiolitis

obliterans

42% of

bronchiolitisobliterans

patients

Rare

Antibody deficiencyPost-infective?

Immuosuppressive therapy?

Lung transplant Associated with bronchiolitis

obliterans

Unknown Rare

Post-infective?

Immuosuppressive therapy?

Other solid organ transplant Post-infective? Rare? Rare

Immuosuppressive therapy?HIV infection Recurrent pneumonia 6–16% Unknown - depends on

incidence of HIV

Associated with LIP

Low CD4 countPost-tuberculosis?

COPD Impaired mucosal immunity? f50%severe COPD

Potentially common

CVID: common variable immunodeficiency; Ig: immunoglobulin; TAP: transporter antigen peptide; CLL: chronic

lymphocytic leukaemia; HSCT: haematopoietic stem cell transplantation; COPD: chronic obstructive pulmonarydisease; TACI: transmembrane regulator, calcium modulator and cyclophilin ligand interactor; ICOS: inducible

T-cell surface expressed CD28 co-stimulatory molecule; STAT3: signal transducer and activator of transcription

3; LIP: lymphocytic interstitial pneumonitis. #: treated with intravenous Ig (IVIG) ": consider treatment with IVIG.

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accounts for 10–20% of cases, generally with an autosomal dominant inheritance pattern (oftenwith partial penetrance); although many of the more recently identified genetic defects associatedwith CVID have an autosomal recessive inheritance pattern. For the majority of patients themolecular defects causing CVID are not known, but in 10–15% mutations affecting Ig productionhave been described. These include mutations of the inducible T-cell surface expressed CD28 co-stimulatory molecule (,1% CVID); the B-cell activating factor receptor (,1% CVID); the CD19component of the co-receptor for the B-cell antigen receptor (,1% CVID); the transmembrane

regulator, calcium modulator and cyclophilin ligand interactor (10–15% CVID); and a B-cellsurface receptor involved in B-cell proliferation [8, 12]. These mutations affect quite differentparts of the immunological response required for antibody production, suggesting that themolecular causes of CVID are heterogeneous and perhaps explaining why there is a large range of clinical associations with CVID that only affect a proportion of patients [13]. For example, up to25% of patients with CVID also develop autoimmune and lymphoproliferative complicationsincluding granulomatous disease, lymphocytic infiltrations of the lungs or lymphoma [7, 10,11, 14]. Although these complications have been particularly associated with known geneticpolymorphisms, variations in gene dosage and penetrance has frustrated attempts to generaterobust clinical phenotype–genotype classifications [15–17]. Most patients seem to be susceptible

to respiratory and gastrointestinal infections, although selection bias and small numbers meansthat the precise incidence of respiratory tract complications in CVID varies between pub-lications. In a large French series encompassing the national experience of patients with CVID,pneumonia occurred in 58% (31% due to S. pneumoniae and 12% due to H. influenzae ),bronchitis in 69% and sinusitis in 63% of patients [11]. In total, 37% of patients were diagnosedwith bronchiectasis. The pattern of bronchiectasis in CVID tends to be diffuse lower and middlelobe disease associated with chronic upper respiratory tract symptoms, similar to idiopathicbronchiectasis [5–7].

CVID is characterised by reduced serum IgG concentrations, so finding levels of serum IgG below the normal range will identify nearly all potential cases. Patients with low IgG levels (even if just

above the bottom of the normal range) should be further evaluated initially by measuring:1) serum IgA, IgM and IgE; 2) IgG subclasses; and 3) levels of specific antibodies (against forexample, tetanus toxin, pneumococcal serotype-specific capsular polysaccharide and H. influenzae capsular polysaccharide B) before and following vaccination if appropriate. More detailedinvestigations, usually conducted by clinical immunologists, include B-cell and T-cell immu-nophenotyping and T-cell proliferative responses to common mitogens (to subclassify CVID andexclude T-cell immunodeficiency). Patients will most likely require lifelong Ig replacementtherapy. The main complications of therapy are fever, headache and chills, which are managedthrough pre-medication with anti-histamines and hydrocortisone. Anaphylactic reactions are rare.Ig replacement may be given by intravenous infusion (i.v. Ig (IVIG), 400 mg?kg-1 every 3–4 weeks)

or by subcutaneous injection (100 mg?kg-1 weekly). Although there are few data on the long-termconsequences of IVIG treatment, IVIG reduces the incidence of respiratory tract infections[18–20] and computed tomography (CT) scores of inflammation associated with bronchiectasis[21], so is likely to prevent or slow the progression of bronchiectasis. Early identification of CVIDcases is therefore important, and measuring serum IgG levels in all cases of bronchiectasis isrecommended in the recent British Thoracic Society guidelines [22]. CVID patients are often givenprophylaxis with continuous low-dose oral antibiotics as well as IVIG therapy. The long-termprognosis of bronchiectasis in CVID patients is not known, but chronic lung disease is aprominent cause of death for CVID patients [23]. Historically, the dose of replacement IVIG givenis based on a trough IgG level with the objective of keeping this within the normal range (7–

15 g?L-1

). Generally, this results in most patients running a trough IgG at the lower end of thenormal range, but recent data suggests that for some patients this is inadequate to keep them freeof infection. Individualised Ig therapy using a dose that prevents infection has therefore beenadvocated to minimise the risk of progressive lung disease [24].

Long-term management of patients with CVID should also include: 1) optimised treatment of their bronchiectasis focusing on appropriated oral and/or nebulised antibiotic prophylaxis

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(as discussed by HAWORTH [25]), anti-inflammatory therapy (described by SMITH et al. [26]) andairway clearance strategies (described by BYE et al. [27]); 2) vigilance for the development of lymphoma, lymphoproliferative lung infiltration and granulomatous disease (although there is noconsensus on the type or frequency of screening [28]); 3) a low threshold for investigation of gastrointestinal symptoms or B12/folate deficiency to pick up CVID-associated inflammatory enteropathy and Giardia infection; and 4) specialist management of associated idiopathicthrombocytopenic purpura and other autoimmune disease if present.

X-linked agammaglobulinaemia

XLA is a rare disorder of B-cell development characterised by absent serum antibodies and nocirculating B-lymphocytes. It is usually caused by inherited mutations in the Btk gene, althoughclinically similar autosomal recessive diseases have been described due to other mutations affectingB-cells [7]. Patients present with recurrent bacterial and viral infections in early childhood. Similarto CVID, patients with XLA are particularly susceptible to infections caused by encapsulatedbacteria such as S. pneumoniae and H. influenzae . As a consequence of recurrent lung infection,lung disease can develop bronchiectasis; in one survey 32% of adult patients with XLA had chronic

lung disease, mainly bronchiectasis [29]. The relative risk of developing structural lung damage is,however, reported to be less with XLA compared with CVID [20]. XLA has been associated withup to 3% of cases of childhood bronchiectasis [5] but is only a rare cause in adults. No specificpattern of bronchiectasis in patients with XLA has clearly been described. The long-term prognosishas improved with aggressive treatment with IVIG and antibiotic therapy, although there are few data on the rate of progression of bronchiectasis and chronic lung disease remains a significantcause of death [29].

IgA, IgM and IgG subclass deficiencies

In case series of paediatric and adult patients with bronchiectasis, small numbers of patients haveselective IgM (,1%), IgA (2%) [3] or IgG subclass deficiency [30–32]. However, the clinicalsignificance of deficiency of IgM or IgA with normal IgG remains unclear. The incidence of isolated IgM deficiency in the normal population is not known and whether IgM can mediateimmunity at the mucosal surface has not been clarified. IgA is present at mucosal surfacesincluding the airway lining fluid [33] and is thought of as an important component of mucosalimmunity. IgA deficiency is relatively common [3, 9], with a prevalence of 1 in 600 of thepopulation, but may be more likely to lead to lung damage if combined with IgG subclassdeficiencies or specific antibody responses to carbohydrate antigens (see later) [34]. IgG subclassdeficiency, especially IgG2, has been associated with bronchiectasis, particularly in children.

However, the incidence of IgG subclass deficiency varies widely in patients with bronchiectasis,from 4% to 48% [3, 6, 30, 35, 36] and the significance of subclass deficiency has been questionedas it is relatively common in a normal population [37]. IgG2 deficiency may be associated withreduced natural or vaccine-induced specific antibody to S. pneumoniae or H. influenzae asdiscussed later. As such, IgG2 deficiency may reflect poor antibody responses to the bacteria thatare associated with bronchiectasis and thus represent a risk factor for disease [38]. Overall, atpresent there is no clear consensus that identification of isolated IgA, IgM or IgG subclassdeficiency in a patient with bronchiectasis is necessarily clinically relevant [6].

Specific antibody deficiency

The high incidence of bronchiectasis in patients with hypogammaglobulinaemia is probably relatedto lack of antibody-mediated immunity to the encapsulated respiratory pathogens S. pneumoniae and H. influenzae . Antibody responses to S. pneumoniae and H. influenzae that recognise capsularpolysaccharides are protective, and hence a number of groups have explored whether selectivedeficiencies in antibody responses to polysaccharide antigens could also cause bronchiectasis.Antibody responses to polysaccharide antigens are described as being T-independent and generated

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through mechanisms that are different from T-dependent antigens [39]. Distinct B-cell sub-populations respond to polysaccharide antigens and patients who have poor responses to capsularpolysaccharide vaccines or who lack particular B-cell subpopulations are particularly susceptible toS. pneumoniae pneumonia [40] and perhaps the development of bronchiectasis [41]. Antibody responses to polysaccharide antigens can be tested by evaluating capsule-antigen specific responsesafter vaccination against S. pneumoniae or H. influenzae , and can be compared with antibody responses to a protein antigen vaccine, such as diptheria or tetanus [42]. Specific antibody deficiency

has been identified in 58% of patients with idiopathic bronchiectasis [38], but this was a small study in which the immunological criteria used for specific antibody deficiency has been queried [43].Other larger series of adult patients with bronchiectasis suggest specific antibody deficiency has anincidence varying from 4% to 11% [3, 41]. In some cases, an impaired specific antibody response wasassociated with selected IgG subclass deficiencies [36]. However, antibody responses to vaccinationwith polysaccharide antigens are variable and affected by age. Up to 10% of the normal populationmay be nonresponders [44, 45]. Hence it is difficult to evaluate the significance of specific antibody deficiency as a cause of bronchiectasis without further studies involving large numbers of bronchiectasis patients and matched controls. Furthermore, naturally acquired immunity to at leastS. pneumoniae may actually be partially dependent on antibody responses to protein rather than

capsular antigens [46], undermining the reasoning why a specific defect in carbohydrate responsescould cause bronchiectasis.

Other PIDs and bronchiectasis

There are many other immunodeficiencies reported to lead to recurrent lung infection, many of which have been associated with bronchectasis. Although often very rare, these diseases are of importance as they indicate which components of the immune response are necessary forpreventing recurrent bacterial infections of the lung.

Transporter antigen peptide deficiency syndrome

Transporter antigen peptide (TAP) proteins are required for the transfer of peptide antigens fromthe cytosol into the endoplasmic reticulum where they associate with human leukocyte antigen(HLA)-1 for presentation on cell surfaces. Autosomal recessive mutations in the TAP1 or TAP2 genes result in reduced HLA-1 expression and CD8 lymphocyte numbers, but with an increase innatural killer (NK) and cd T-cells [47, 48]. The majority of subjects with TAP deficiency haverecurrent sino-pulmonary infections with common respiratory tract bacterial pathogens anddevelop bronchiectasis [47, 48]. Only a handful of families with TAP deficiency have beendescribed, and this genetic defect will be responsible for a vanishingly small proportion of cases of

bronchiectasis. However, the association of TAP deficiency and other very rare familial T-celldisorders [49, 50] with bronchiectasis demonstrates that there are previously unsuspectedmechanisms of immunity to extracellular bacterial pathogens involving CD8 lymphocytes thatrequires further investigation. In addition, it has been suggested that an excess of NK and cd T-cells might promote bronchiectasis due to a dysregulated inflammatory response in reply toinfection with bacterial pathogens [48].

Disorders of macrophage or neutrophil function

There are a wide range of inherited disorders affecting neutrophil function such as chronic

granulomatous disease (CGD), leukocyte adhesion deficiency and Chediak–Higashi syndrome[51]. Although these disorders are extremely rare, making it difficult to accurately evaluate theirclinical associations, neutrophil disorders classically lead to recurrent pneumonia and abscessesbut are not necessarily closely associated with bronchiectasis. In relatively large series of adultpatients with bronchiectasis, tests of neutrophil function only occasionally identify patients withabnormal responses and even in these patients the relationship of the defect to bronchiectasis isnot clear [2, 3, 5]. CGD has been associated with cases of bronchiectasis in some paediatric case

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reports or case series but these reports are likely to have been affected by selection bias as they originate from specialist centres [2, 5, 52]. The seemingly weak association of neutrophil defectswith bronchiectasis may also reflect the range of pathogens these patients are most susceptible to,which include Staphylococcus aureus , Nocardia , Aspergillus and Candida species but excludesS. pneumoniae and H. influenzae , the pathogens most closely associated with development of bronchiectasis in Ig deficiencies [51]. Primary defects of macrophage function generally affectintracellular killing and lead to increased incidences of infection with intracellular pathogens such

as mycobacteria, Histoplasma , Listeria and Salmonella species [51] but again are generally notdirectly associated with the development of bronchiectasis. What is unclear is the extent to whichfunctional polymorphisms of phagocytic receptors (such as Fc gamma RIIA H/R 131) or patternrecognition receptors (such as Toll-like receptors) may predispose to bronchiectasis throughimpaired phagocytosis of opsonised/non-opsonised bacteria or aberrant inflammatory responses.

Hyper IgE syndrome

Hyper IgE syndrome is a rare autosomal dominant inherited syndrome that causes susceptibility to arange of infections as well as bone, dental, vascular and joint abnormalities [53]. Most patients have

the classical clinical triad of massively raised IgE levels, recurrent pneumonia and soft tissue abscesses(hence the condition is also called Job’s syndrome). The majority of cases are caused by mutationsaffecting the signal transducer and activator of transcription 3, an intracellular signalling proteinimportant for regulating cellular responses to cytokines [53, 54]. Patients have both an exaggeratedand reduced cytokine response to infection. In particular, patients with hyper IgE syndrome have animpaired T-helper cell type 17 (Th17) CD4 response [55], which seems to be important for mucosalimmunity to some respiratory pathogens such as Klebsiella pneumoniae and S. pneumoniae [56, 57],as well as S. aureus [58] and Candida species [59]. Th17 CD4 immune responses assist neutrophilrecruitment to sites of infection as well as local mucosal immunity [56, 57]. Pneumonia in patientswith hyper IgE syndrome is often complicated by pneumatoceles, but can also lead to

bronchiectasis in a significant proportion of patients [53]. Although hyper IgE syndrome is a raredisease that is only occasionally found in cases series of patients with bronchiectasis [2, 5], theidentification that the underlying genetic defect of a Th17 response demonstrates the importanceof this pathway for immunity to common bacterial pathogens of the lung.

Other PIDs associated with bronchiectasis

Patients with inherited disorders of DNA repair such as ataxia telangiectasia are more susceptible toinfections as the development of adaptive immunity is impaired. Many of these patients are antibody deficient and have bronchiectasis [60]. Similarly Wiskott–Aldrich syndrome, an X-linked

immunodeficiency caused by mutations in the WASP gene leading to low levels of T- and B-lymphocytes, NK cells and serum IgM, develop infections with encapsulated organisms andtherefore are at risk of bronchiectasis [61]. Both these disorders are rare causes of bronchiectasis inpaediatric case series [2, 5]. A major component of immunity to extracellular bacterial pathogens isthe complement system, and inherited complement deficiencies such as C2 or mannose-bindinglectin (MBL) deficiency are associated with recurrent respiratory infections [62, 63]. However,although MBL deficiency is a relatively common condition affecting up to 25% of the normalpopulation [62] there are only occasional reports linking isolated MBL deficiency withbronchiectasis [5]. MBL deficiency may increase the likelihood of bronchiectasis in patients withCVID [64–66] and is associated with more severe disease in patients with cystic fibrosis (CF) [67],

suggesting MBL may help control disease progression in other immunodeficiencies associated withbronchiectasis. Lower levels of L-ficolin, another MBL pathway opsonin, has also been found inpatients with bronchiectasis compared with controls [68], although these data need to be replicated.Other complement deficiencies are very rare and there are no data linking them to bronchiectasis.

The majority of patients with CF and ciliary dyskinesias will develop bronchiectasis and clearly have impaired physical immune defences of the lung through the effects of the gene defects on

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mucociliary clearance. Neither are usually characterised as immunodeficiencies. However, recentdata suggest mutations of the CF transmembrane conductance regulator in CF also cause a variety of defects in mucosal innate immunity. These include impaired phagocyte function, reducedefficacy of antibacterial peptides, and failure of bacterial internalisation by epithelial cells, as well asan exaggerated inflammatory response to infection [69, 70]. This constellation of multiple defectsin innate immunity could make a significant contribution to the development of bronchiectasis inpatients with CF, but this will be difficult to establish conclusively.

Secondary immunodeficiencies

Good clinical data on the associations of different secondary immune deficiencies withbronchiectasis are more limited than the available data for PIDs. In general an accurateassessment using the published data of the importance of SIDs as causes of bronchiectasis is notpossible. However, recognised causes of SIDs are probably relatively rare causes of bronchiectasis,with the potential exception of children in areas with a high incidence of HIV infection.

Haematological malignancies

Many haematological malignancies result in B-cell and/or T-cell dysfunction and predispose torecurrent lung infection and subsequent development of bronchiectasis. In addition, profoundimmunodeficiency may occur as a result of treatment for these conditions. Case reports or caseseries have described bronchiectasis complicating chemotherapy, acute and chronic leukaemias,myeloma and lymphomas [5, 71–73]. In particular, due to the combination of prolonged survivaland the high frequency of secondary hypogammaglobulinaemia, multiple myeloma and chroniclymphocytic leukaemia (CLL) seem to be relatively commonly associated with bronchiectasis,although the exact incidence has not been reported [72]. CLL and myeloma patients with provenbronchiectasis and hypogammaglobulinaemia should be assessed for IVIG therapy. Bronchiectasis

has also been reported to develop in association with more acute haematological malignancies,perhaps as a consequence of severe lung infections and/or due to the affects of leukaemia orchemotherapy on host immunity [71]. However, there are no precise data on the incidence andrate of progression of bronchiectasis in patients with haematological malignancies.

Post-transplantation

Haematopoietic stem cell transplantation (HSCT) is associated with an increased incidence of respiratory infections and potentially prolonged defects in cellular and humoral immunity insurvivors [74]. These factors could predispose to bronchiectasis [75] and, in the authors’

experience, serial CT scans after allograft HSCT can demonstrate rapidly developing bronchiectasisover a period of weeks to months. In addition, up to 10% of HSCT allograft recipients will developbronchiolitis obliterans (the main pulmonary manifestation of graft versus host disease) whichprecedes the appearance of diffuse bronchiectasis in ,40% of cases [76, 77]. Hence, although thereare no precise prevalence data on bronchiectasis post-HSCT, it is probably a relatively commoncomplication, especially in allograft recipients. Similarly, patients who develop bronchiolitisobliterans after lung transplantion may also have CT evidence of bronchiectasis [78], and there arecase reports of bronchiectasis developing after transplantation of other solid organs [79],presumably because of damage caused by intercurrent pneumonias and/or impaired pulmonary immunity due to prolonged immunosuppressive therapy.

HIV

HIV infection in most patients leads to a progressive T-cell defect characterised by a fall in CD4 T-helper cells. HIV-infected subjects suffer recurrent infections with conventional and opportunisticpulmonary pathogens, including mycobacteria species and S. pneumoniae . With the increasingduration of long-term survival after HIV infection it is therefore perhaps not surprising that up to

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16% of HIV-infected children develop bronchiectasis [80, 81]. The incidence of bronchiectasis inHIV-infected adults may also be significant [82, 83]. The aetiology of HIV-related bronchiectasis isnot well understood but may include direct effects of HIV infection on T-cell-dependentimmunity and local macrophage- and monocyte-dependent pulmonary immunity, secondary effects on humoral responses, as well as direct effects of bronchial wall damage due to intercurrentpneumonia or tuberculosis, and possibly the association of HIV in adults with chronic obstructivepulmonary disease (COPD) [84]. The limited available publications suggest that in children

bronchiectasis is more likely in subjects with CD4 counts ,100 mm3

, or who have had recurrentpneumonia [80]. Interestingly, there is also a specific association with lymphocytic interstitialpneumonitis (LIP), with up to 40% of HIV-infected children with LIP developing bronchiectasis[80, 85]. Whether this reflects accelerated bronchial wall damage due to the lymphocytic infiltrateor reduced mucosal immunity in LIP is not clear. There are no comparative data on the patternand progression of bronchiectasis in HIV-positive patients compared with patients withbronchiectasis due to other causes. More studies are required on the prevalence and associationsof HIV infection with both adult and paediatric bronchiectasis to allow specific risk groups to bedefined and managed aggressively to prevent progressive bronchiectasis. In addition, in areas withsignificant levels of HIV infection whether patients diagnosed with bronchiectasis warrant a HIV

test as part of the diagnostic work-up needs consideration.

COPD and asthma

There is a high incidence of bronchiectasis in patients with severe asthma and COPD according toCT criteria [86, 87], although the exact incidence is not known and is confounded by both asthmaand irreversible airways obstruction being complications of bronchiectasis. Bronchiectasis couldbe associated with asthma and COPD due to the cycles of recurrent infection and localisedbronchial wall inflammation associated with both conditions. The clinical importance of bronchiectasis in patients with airways disease is not clear at present, but as bacterial infections

frequently drive exacerbations of COPD, significant bronchiectasis could be clinically highly relevant. Patients with asthma and COPD may have altered mucosal immune responses tomicrobial pathogens and impaired macrophage function that, along with the marked airway inflammation that characterises both diseases, might contribute towards the development of bronchiectasis [88, 89]. The effects of asthma and COPD on pulmonary immunity need furtherinvestigation. Due to the rising incidence of COPD and more extensive use of CT scanning, severeCOPD is likely to become an increasingly common association in series of adult patients withbronchiectasis.

Biological therapies

Therapies that inhibit tumour necrosis factor-a (such as infliximab) or deplete B-cells (rituximab)are increasingly used to treat rheumatological and other autoimmune conditions. Both therapies areassociated with increased risks of infection [90, 91]. These therapies may make management of existing bronchiectasis more challenging and, in our experience, usually require an escalation of antibiotic prophylaxis. Furthermore, they could potentially trigger the development of bronch-iectasis by increasing the frequency and/or severity of respiratory infections. Repeated administra-tion of rituximab is often associated with the development of hypogammaglobulinaemia, which inthe context of recurrent infection, should be managed by immunoglobulin replacement [92]. Theeffects of biological therapies are discussed in detail in the chapter by DHASMANA and WILSON [93].

What information do PIDs and SIDs provide about immunity toairways infection?

The identification of patients with bronchiectasis due to PIDs provides clear evidence for whichaspects of the immune system are required for protection against bacterial infections of the lung.

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The close association of bronchiectasis with CF, primary ciliary dyskinesia and antibody deficiency syndromes such as CVID and XLA demonstrate that physical defences and IgG (and perhaps IgA,specific IgG subclasses or anti-polysaccharide antibody responses) are required for the prevention of chronic bacterial infection of the lungs, as discussed in the chapter by LAMBRECHT et al . [94].Although the mechanisms remain poorly defined, the clinical manifestations of TAP deficiency andhyper IgE syndrome with bronchiectasis suggest there is also an important and previously unsuspected role for CD8 and Th17 CD4 lymphocytes for the prevention of bacterial lung infection.

Conversely, despite the prominence of neutrophil and macrophage infiltration in pneumonia andbacterial bronchitis, defects of phagocyte and complement function are only loosely associated withbronchiectasis. Humoral immunity therefore seems to be more important for bacterial clearancefrom the bronchial tree than phagocytes. This is perhaps a surprising observation as the mainmechanism by which antibody assists pulmonary immunity to bacterial infection would have beenpredicted to be through promoting bacterial phagocytosis. Despite these clues provided by PIDs andSIDs, large gaps remain in our knowledge on the immune mechanisms required to prevent bacterialinfections of the lung. Specific important areas of future research include the mechanisms by whichantibody promotes clearance of bacteria from the lung, the bacterial target antigens for theseantibody responses, and the role of different T-cell subsets for lung immunity.

A strategy for immunological investigation of patients withbronchiectasis

We recommend a sequential approach to investigation of immune function in patients withbronchiectasis or recurrent infection summarised in table 2. First-line investigations involvemeasurement of total serum Ig, IgG subclasses and specific antibody levels before and aftervaccination (to detect CVID, XLA, IgA/IgM and IgG subclass deficiency) and, where appropriate,test for HIV infection. Further testing can then be initiated (following discussion with a clinical

immunologist). Second-line tests include T- and B-cell immunophenotyping (to examine fordefects in lymphocyte differentiation), neutrophil superoxide measurements (to look for CGD)and complement (to check for deficiency). A number of third-line tests involving gene sequencingand functional assays (examples shown in table 2) may also be indicated. One important clue tothe type of immunodeficiency is the type of infections affecting the patient which can direct

Table 2. Suggested staged immunological investigations of patients with bronchiectasis

First-line tests Second-line tests Third-line tests

Serum IgG, IgA, IgM, IgE Immunophenotyping

(including B-cell subsets)

Specific gene sequencing

(e.g. ICOS, TACI, STAT)IgG subclasses Targetted genotyping

(MBL, FccRIIa)

TCR V b usage

Levels of specific antibodies against:

pneumococcal serotype specificcapsular polysaccharide, tetanus toxin

If low, assess vaccination response

Neutrophil superoxide TCR spectratyping

Autoantibody screen Complement levels Functional assays

(e.g. chemotaxis, cytokine

release assays,

phagocytosis and bacterial

opsonisation assays)White cell differential count

HIV test

Ig: immunoglobulin; MBL: mannose-binding lectin; ICOS: inducible T-cell surface expressed CD28 co-stimulatory molecule; TACI: transmembrane regulator, calcium modulator and cyclophilin ligand interactor;

STAT: signal transducer and activator of transcription 3; TCR: T-cell receptor.

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laboratory investigations: encapsulated bacteria in B-cell immunodeficiencies; fungi, viruses andmycobacteria in T-cell immunodeficiencies and catalase-positive organisms (e.g. Staphylococcus ,Aspergillus ) in neutrophil disorders.

Future directions

26–53% of patients with bronchiectasis have no defined cause [3, 4]. Many of these patients alsohave upper respiratory tract disease such as sinusitis, suggesting they may have a global defect inpreventing chronic bacterial infection of the respiratory tract. Recently, there has been increasingevidence that unsuspected immune defects may underpin many childhood infectious diseases [95]and intensive screening of children with idiopathic bronchiectasis may identify additional PIDs.For example, as untreated patients with primary ciliary dyskinesia and CF almost always developsignificant bronchiectasis, other more minor defects in physical defences could be importantcauses of idiopathic bronchiectasis in adults and children. However, redundancy may limit therole of immunological defects as causes of bronchiectasis. For example, even with significant IgGdeficiency the clinical phenotype of bronchiectasis has only partial penetrance and a significantproportion of subjects do not develop chronic lung infection. Hence, in adults, bronchiectasiscould be a multifactorial disorder requiring two or more immune defects or a combination of animmune defect with a specific environmental insult in order to develop. The role of many aspectsof lung immunity such as mucosal anti-bacterial peptides and proteins have yet to be investigated,and the complexity of the respiratory immune system could make identifying novel immunedefects associated with bronchiectasis difficult. Despite this, polymorphisms affecting NK cellfunction or TAP and HLA associations with bronchiectasis have been described [96–98]. Furthergenetic studies of large numbers of patients with bronchiectasis are likely to identify additionalpolymorphisms or mutations affecting different aspects of immune function which could berelated to the development of bronchiectasis.

Conclusions

Characterisation of patients with bronchiectasis has demonstrated close associations with a widerange of PIDs and SIDs, confirming that effective pulmonary immunity is necessary to preventchronic bronchial damage due to bacterial infection. PIDs associated with bronchiectasis provideclear evidence for the vital role of physical defences for preventing lung infection, with importantsupportive roles from antibody and T-cell. SIDs causing bronchiectasis are less well characterised,but the effects of long-term HIV infection, the new biological therapies and perhaps chronicairways disease on pulmonary immunity are likely to be increasingly associated with the

development of bronchiectasis. Patient with SID should be monitored for the development of recurrent lung infections and, where appropriate, the development of hypogammaglobulinaemia.

Despite intense investigation for all the known causes of bronchiectasis, a large proportion of patients will still have idiopathic disease. An even more detailed immunological assessment of patients with idiopathic bronchiectasis combined with investigations for novel gene defects andpolymorphisms will probably reveal a range of minor defects that affect immune function in asignificant proportion of these patients. Although the challenge will then be to confirm that theseminor immune defects actually contribute to the development of bronchiectasis, we would predictthat increasing numbers of immunodeficiencies associated with bronchiectasis will be identified inthe future.


H. Baxendale has received research grant funding from Biotest and GlaxoSmithKline PLC toexplore natural and vaccine related immunity to Streptococcus pneumoniae . Travel to ESI 2010biannual meeting was funded by Grifols UK, Ltd.

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manifestations, and treatment. Biol Blood Marrow Transplant 2009; 15: 84–90.

62. Eisen DP. Mannose-binding lectin deficiency and respiratory tract infection. J Innate Immun 2010; 2: 114–122.63. Jonsson G, Truedsson L, Sturfelt G, et al. Hereditary C2 deficiency in Sweden: frequent occurrence of invasive

infection, atherosclerosis, and rheumatic disease. Medicine (Baltimore) 2005; 84: 23–34.

64. Gregersen S, Aalokken TM, Mynarek G, et al. Development of pulmonary abnormalities in patients with common

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65. Litzman J, Freiberger T, Grimbacher B, et al. Mannose-binding lectin gene polymorphic variants predispose to the

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66. Aghamohammadi A, Foroughi F, Rezaei N, et al. Mannose-binding lectin polymorphisms in common variable

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67. Garred P, Pressler T, Madsen HO, et al. Association of mannose-binding lectin gene heterogeneity with severity of

lung disease and survival in cystic fibrosis. J Clin Invest 1999; 104: 431–437.

68. Kilpatrick DC, Chalmers JD, MacDonald SL, et al. Stable bronchiectasis is associated with low serum L-ficolin

concentrations. Clin Respir J 2009; 3: 29–33.

69. Moskwa P, Lorentzen D, Excoffon KJ, et al. A novel host defense system of airways is defective in cystic fibrosis.


70. Doring G, Gulbins E. Cystic fibrosis and innate immunity: how chloride channel mutations provoke lung disease.

Cell Microbiol 2009; 11: 208–216.

71. Kearney PJ, Kershaw CR, Stevenson PA. Bronchiectasis in acute leukaemia. Br Med J 1977; 2: 857–859.

72. Knowles GK, Stanhope R, Green M. Bronchiectasis complicating chronic lymphatic leukaemia with

hypogammaglobulinaemia. Thorax 1980; 35: 217–218.

73. Okada F, Ando Y, Kondo Y, et al. Thoracic CT findings of adult T-cell leukemia or lymphoma. AJR Am J

Roentgenol 2004; 182: 761–767.

74. Parkman R. Antigen-specific immunity following hematopoietic stem cell transplantation. Blood Cells Mol Dis

2008; 40: 91–93.

75. Morehead RS. Bronchiectasis in bone marrow transplantation. Thorax 1997; 52: 392–393.

76. Gunn ML, Godwin JD, Kanne JP, et al. High-resolution CT findings of bronchiolitis obliterans syndrome after

hematopoietic stem cell transplantation. J Thorac Imaging 2008; 23: 244–250.

77. Tanawuttiwat T, Harindhanavudhi T. Bronchiectasis: pulmonary manifestation in chronic graft versus host disease

after bone marrow transplantation. Am J Med Sci 2009; 337: 292.

78. de Jong PA, Dodd JD, Coxson HO, et al. Bronchiolitis obliterans following lung transplantation: early detection

using computed tomographic scanning. Thorax 2006; 61: 799–804.

79. Pijnenburg MW, Cransberg K, Wolff E, et al. Bronchiectasis in children after renal or liver transplantation:

a report of five cases. Pediatr Transplant 2004; 8: 71–74.

80. Berman DM, Mafut D, Djokic B, et al. Risk factors for the development of bronchiectasis in HIV-infected children.


81. Sheikh S, Madiraju K, Steiner P, et al. Bronchiectasis in pediatric AIDS. Chest 1997; 112: 1202–1207.

82. Holmes AH, Pelton S, Steinbach S, et al. HIV related bronchiectasis. Thorax 1995; 50: 1227.

83. Holmes AH, Trotman-Dickenson B, Edwards A, et al. Bronchiectasis in HIV disease. Q J Med 1992; 85: 875–882.84. Crothers K, Butt AA, Gibert CL, et al. Increased COPD among HIV-positive compared to HIV-negative veterans.

Chest 2006; 130: 1326–1333.

85. Amorosa JK, Miller RW, Laraya-Cuasay L, et al. Bronchiectasis in children with lymphocytic interstitial pneumonia

and acquired immune deficiency syndrome. Plain film and CT observations. Pediatr Radiol 1992; 22: 603–606.

86. Patel IS, Vlahos I, Wilkinson TM, et al. Bronchiectasis, exacerbation indices, and inflammation in chronic


87. Paganin F, Seneterre E, Chanez P, et al. Computed tomography of the lungs in asthma: influence of disease severity

and etiology. Am J Respir Crit Care Med 1996; 153: 110–114.

88. Taylor AE, Finney-Hayward TK, Quint JK, et al. Defective macrophage phagocytosis of bacteria in COPD. Eur

Respir J 2010; 35: 1039–1047.

89. Contoli M, Message SD, Laza-Stanca V, et al. Role of deficient type III interferon-lambda production in asthma

exacerbations. Nat Med 2006; 12: 1023–1026.90. Lieberman-Maran L, Orzano IM, Passero MA, et al. Bronchiectasis in rheumatoid arthritis: report of four cases

and a review of the literature–implications for management with biologic response modifiers. Semin Arthritis

Rheum 2006; 35: 379–387.

91. Cooper N, Arnold DM. The effect of Rituximab on humoral and cell mediated immunity and infection in the

treatment of autoimmune disease. Br J Haematol 2010; 149: 3–13.

92. Cooper N, Davies EG, Thrasher AJ. Repeated courses of rituximab for autoimmune cytopenias may precipitate

profound hypogammaglobulinaemia requiring replacement intravenous immunoglobulin. Br J Haematol 2009;

146: 120–122.

93. Dhasmana DJ, Wilson R. Bronchiectasis and autoimmune disease. Eur Respir Mon 2011; 52: 192–210.

94. Lambrecht BN, Neyt K, GeurtsvanKessel CH. Pulmonary defence mechanisms and inflammatory pathways in

bronchiectasis. Eur Respir Mon 2011; 52: 11–21.

95. Casanova JL, Abel L. Human genetics of infectious diseases: a unified theory. EMBO J 2007; 26: 915–922.96. Dogru D, Ozbas Gerceker F, Yalcin E, et al. The role of TAP1 and TAP2 gene polymorphism in idiopathic

bronchiectasis in children. Pediatr Pulmonol 2007; 42: 237–241.

97. Boyton RJ, Smith J, Ward R, et al. HLA-C and killer cell immunoglobulin-like receptor genes in idiopathic


98. Boyton RJ, Smith J, Jones M, et al. Human leucocyte antigen class II association in idiopathic bronchiectasis, a

disease of chronic lung infection, implicates a role for adaptive immunity. Clin Exp Immunol 2008; 152: 95–101.

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Chapter 13

Bronchiectasis and

autoimmune diseaseD.J. Dhasmana and R. Wilson

Summary

The association between bronchiectasis and autoimmune

disease is well recognised, and best described with rheumatoidarthritis. The prevalence of bronchiectasis in rheumatoidarthritis varies considerably in studies, with obliterativebronchiolitis a common feature. The prognosis of rheumatoidarthritis with bronchiectasis seems to be worse than eithercondition alone. The advent of high-resolution computedtomography has increased the sensitivity of detecting bronch-iectasis, but this should be assessed for clinical significance.Traction bronchiectasis results from interstitial fibrosis pulling

the airway wider, rather than damage weakening the bronchial wall, and is less likely to lead to bronchial suppuration.Bronchial wall damage in bronchiectasis is caused by inflam-mation, but it is difficult to differentiate damage caused by severe or recurrent infections, predisposed to by immunosup-pression related to the autoimmune disease itself or itstreatment, from damage caused by the autoimmune process.Increased use of new immunomodulatory or immunosuppres-sive agents has proved successful in modifying autoimmunedisease processes, but has also led to emergence of infectivecomplications that can cause bronchiectasis or exacerbate pre-existing disease.

Keywords: Autoimmune, bronchiectasis, immunosuppression,rheumatoid arthritis, Sjogren’s syndrome, vasculitis

Host Defence Unit, Royal BromptonHospital, London, UK.

Correspondence: R. Wilson, RoyalBrompton Hospital, Fulham Road,London, SW3 6NP, UK, [email protected]


A

n association between bronchiectasis and autoimmune disease has long been recognised. The

main autoimmune diseases in which bronchiectasis has been described are discussed in thischapter with emphasis on rheumatoid arthritis, for which there is best evidence of a trueassociation. When information is available we discuss estimated prevalence, pathogenesis, clinicalfeatures and management where this differs from that in usual bronchiectasis and prognosis. Inaddition, we have discussed screening and risk stratification in the context of immunosuppressionfollowing the use of biological agents such as anti-tumour necrosis factor (TNF) in autoimmunedisease.

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There are several recurringthemes that are worth noting:1) high-resolution computedtomography (HRCT) scan-ning, which has significant-ly increased the sensitivity of imaging of bronchiectasis, was

not available when older stu-dies were performed and sothe diagnosis of bronchiecta-sis may be less certain; 2)presence of radiological bron-chiectasis versus symptomaticdisease; and 3) the use of retrospective data in analysesof complex often heteroge-neous populations. Another

theme is traction bronchiec-tasis that may be present inpatients with lung fibrosis dueto involvement of the lungparenchyma by autoimmunedisease-causing fibrosis. Thescarring pulls the airwaysapart as it contracts. The air-way mucosa is normal withintact mucociliary clearance

and possibly for this reasonpatients are not usually proneto bacterial infections. How-ever, in some cases with trac-tion bronchiectasis there willalso be bronchiectasis in partsof the lung without fibrosis,suggesting that an inflam-matory process has involvedthe airways and damaged the

structure of the bronchial wall.These patients may be moreprone to the clinical syndromeof bronchiectasis. A summary of the features of the mainstudies carried out are shownin table 1.

Autoantibodies should not beroutinely tested for during theinvestigation of a patient withbronchiectasis; they shouldonly be tested for if thereare particular clinical featuresraising autoimmunity as apossible association [50]. Inaddition, rheumatoid factor is

T a b l e 1 . S u m m a

r y o f t h e f e a t u r e s o f b r o n c h i e c t a s i s i n d i f f e r e n t a u t o i m m u n e d i s e a s e s

D i s e a s e

A p p r o x i m a t e p r e v a l e n c e i n

m a i n s t u d i e s

P a t i e n t s e l e c t i o n

a n d s t u d y t y p e

C o m m e n t s

[ R e f . ]

R A

2 – 5 0 %

M i x e d s e l e c t e d a n d u n s e l e c t e d

L a r g e s t b o d y o f d a t a

, v a r i a b l e c o n c l u s i o n s b u t l a r g e s t

e v i d e n c e b a s e o f a u t o i m m u n e d i s e a s e s

[ 1 – 1 2 ]

S j o ¨ r g e n ’ s

, 1 0 – 4 6 %


M o s t d a t a b a s e d o

n i n c i d e n t a l f i n d i n g s o n H R C T ,

p a t i e n t s

o f t e n a s y m p t o m a t i c

[ 1 3 – 1 6 ]

S L E

, 2 – 2 1 %

V a r i o u s , i n c l u d i n g l a r g e

p r o s p e c t i v e a n d c r o s s - s e c t i o n a l

F r e q u e n t f i n d i n g o f b r o n c h

i e c t a s i s o n H R C T b u t p o o r c o r r e

l a t i o n

w i t h s y m p t o m s ; c o m p l i c a t i o n s

o f i n f e c t i o n a n d t h r o m b o s i s a r e

s i g n f i c a n t

a n d m a y d o m i n a t e o v e r c l i n i c a l l y m e a n i n g f u l b r o n c h i e c t a

s i s

[ 1 7 – 1 9 ]

A S

7 – 2 3 %


T r a c t i o n b r o n c h i e c t a s i s

c o m m o n , b u t u s u a l l y a s y m p t o m a

t i c ;

m o r b i d i t y u s u a l l y t h r o u g h n o n - r e s p i r a t o r y c o m p l i c a t i o n s

[ 1 7 , 2 0 – 2 4 ]

S c l e r o d e r m a

f 5 9 %


N S I P , p u l m o n a r y h y p e r t e n s i o n a n d t r a c t i o n b r o n c h i e c t a s i s c o

m m o n ;

p r i m a r y b r o n c h i e c t a s i s l e s s s o a n d p e r h a p s m o r e i n ’ d i f f u s e ’

d i s e a s e

[ 2 5 – 2 9 ]

R P

f 5 0 %


S e v e r a l o l d s t u d i e s p r e - 1 9 8 6 a n d p r e - H R C T s o l i k e l y g r o s s o v e

r e s t i m a t e

[ 3 0 – 3 4 ]

M C T D

1 2 %

V a r i o u s s e l e c t e d

W h e r e p r e s e n t , t r a c t i o n b

r o n c h i e c t a s i s m o r e l i k e l y t h a n p r i m a r y

b r o n c h i e c t a s i s ,

a g a i n u s u a l l y a s y m p t o m a t i c

[ 3 5 – 3 7 ]

P M / D M

R a r e

P r i m a r y b r o n c h i e c t a s i s

n o t d e s c r i b e d

N S I P a n d o r g a n i s i n g p n e u m o n i a c o m m o n , t r a c t i o n b r o n c h i e

c t a s i s

r a r e l y r e p o r t e d a n

d p r i m a r y b r o n c h i e c t a s i s r a r e

[ 3 8 – 4 0 ]

V a s c u l i t i s

V a r i o u s a c c o r d i n g t o t y p e


G r a n u l o m a t o s i s w i t h p o l y a n g i i t i s ( W e g e n e r ’ s ) a n d M P A m o s t c o

m m o n o f

p r i m a r y v a s c u l i t i d e s ; B

P I - A N C A l i n k e d t o P s e u d o m o n a

s

[ 4 1 – 4 9 ]

R A : r h e u m a t o i d a

r t h r i t i s ; S L E : s y s t e m i c l u p u s e r y t h e m a t o s u s ; A S : a n k y l o s i n g s p o n d y l i t i s ; R P : r e l a p s i n g p o l y c h o n d r i t i s ; M C T D : m i x e d c o n n e c t i v e t i s s u e d i s e a s e ; P M / D M :

p o l y m o y o s i t i s / d e r m a t o m y o s i t i s ; H R C T : h i g h - r e s o l u t i o n c o m p u t e d t o m o g r a p h y ; N S I P :

n o n s p e c i f i c i n t e r s t i t i a l p n e u m o n i a

; M P A : m i c r o s c o p i c p o l y a n g i i t i s ; B

P I - A N C A : b a c t e r i c i d a l /

p e r m e a b i l i t y - i n c r e a s i n g p r o t e i n - a n t i n e u t r o p h i l c y t o p

l a s m i c a n t i b o d i e s .

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D . J . D H A S M A N A A N D R . W

I L S O N



nonspecific but high levels do characterise a group of patients with prominent small airwaysdisease in whom immunosuppression should be considered. Anti-cyclic citrullinated peptidewhich is more specific for rheumatoid arthritis has not as yet been investigated in relation tobronchiectasis.

Rheumatoid arthritis

The association of rheumatoid arthritis and bronchiectasis is well described [1, 51] and it is themajor autoimmune condition associated with bronchiectasis. One important question whichremains unanswered is how the two conditions are related and how one develops in the context of the other. One hypothesis is that the initial event is recurrent antigen stimulation from recurrentlower respiratory tract infections, and the immunopathological sequence of events that followsleads to the development of a multi-system inflammatory disorder with a predilection forarthropathy. An alternative hypothesis is that bronchiectasis arises from the immunosuppressionassociated with rheumatoid arthritis itself and/or its treatments.

PrevalenceThe reported prevalence of rheumatoid arthritis with bronchiectasis varies considerably largely due to patient selection and study type. Reports describe between approximately 2% and 50%prevalence of bronchiectasis in the largest studies of rheumatoid arthritis published between 1967and 2006 [1–12]. A major issue is whether radiological evidence of bronchiectasis, either by chestradiography or by HRCT scanning, represents disease that is clinically significant. Studies thathave tried to explore this demonstrate poor correlation with radiology [3, 8, 9, 52]. In moststudies, the prevalence is calculated on the HRCT findings rather than on clinical evidence of bronchiectasis and patients may be entirely asymptomatic with incidental HRCT findings.

Most reports of prevalence have used heterogeneous populations and so carry several potentialconfounding characteristics including duration of illness, age (mean age of 45–64 yrs acrossstudies), cigarette smoking history and drug-treatment schedules, which might include cor-ticosteroids and immunosuppressants, such as methotrexate, which could influence susceptibility to infection. Moreover, the data is typically retrospective bringing with it recall and reporter bias.DESPAUX et al. [8] report prospective data on 46 unselected patients with rheumatoid arthritis(34 females, 12 males; mean age 60.1 yrs) collected over an 18-month period. In this study inwhich all patients had a HRCT, they found 23 (50%) patients with radiological evidence of bronchiectasis, 18 of whom were previously undiagnosed. 13 (57%) of these 18 patients wereasymptomatic, thus giving a total of 22% (10 out of 46 patients) with clinically significant

bronchiectasis. In two other prospective studies of 75 consecutive patients [10] and 63consecutive patients [12] with rheumatoid arthritis, 19% and 29% of patients, respectively, werefound to have bronchiectasis on HRCT, although it is not clear what proportion of these weresymptomatic. A retrospective uncontrolled study of 20 life-long nonsmokers showed a highproportion of bronchiectasis with five (25%) out of 20 demonstrating basal bronchiectaticchanges, but whilst three of these five gave a past history of pleurisy or pneumonia none hadongoing symptoms [3]. In other more heterogeneous studies, sub-group analysis has not beenable to demonstrate a relationship between smoking and bronchiectasis in rheumatoid arthritis[8, 9, 52]. We are not aware of any study that has attempted to correlate the severity of bronchiectasis using one of the accepted scoring systems with severity of arthritis, either in terms

of joint damage or immunological measures.

The immunological diagnosis of rheumatoid arthritis may also complicate prevalence data. Inparticular, there may be other autoimmune diseases present within the population studied, such asSjogren’s syndrome [53, 54]. With modern day biochemical and immunological markers, there isa more robust system to better differentiate autoimmune diseases from one another, which willallow better definition of disease in the future.

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Finally, the patient’s ethnic status may have an additional impact on the development of bronchiectasis with rheumatoid arthritis. This is rarely mentioned within studies. The largestcohorts are described in France close to the Alps [8] and close to the North Atlantic [4], NorthAfrica [9], New England in the USA [2] and in central and northern England, UK [3]. Theantigenic stimulation by community pathogens is likely to vary markedly in these differentsettings.

Pathogenesis

Whilst the association of bronchiectasis and rheumatoid arthritis has long been recognised[1, 8, 51], the mechanisms of how one condition develops in the context of the other remainsunclear. While the co-existence of the two separate conditions is possible, the frequency of bronchiectasis in rheumatoid arthritis is well above that found in the non-rheumatoid arthritispopulation and suggests that these are not chance findings [4, 7, 8]. Three mechanisms have beenconsidered: 1) bronchiectasis gives rise to the development of rheumatoid arthritis; 2) bron-chiectasis and rheumatoid arthritis are caused by similar immunological processes, or because of immunosuppression due to rheumatoid arthritis or its treatments; and 3) other diagnoses and/or

comorbid conditions drive the development of rheumatoid arthritis or bronchiectasis. These willbe discussed in turn, although in reality there may well be several mechanisms interacting in aparticular case.

Bronchiectasis gives rise to the development of rheumatoid arthritis

The nature of the complex immunological mechanisms present in the bronchiectatic airways hasbeen studied. The neutrophil plays a central role in what has been called ‘‘the vicious circlehypothesis’’, but in addition abnormal mucus clearance and cellular immune responses areimportant [55–58]. In this context, one proposed mechanism is that persistent immunological

pressure stimulated by chronic bacterial infection drives a sequence of events that leads to theformation of autoantibodies to ‘‘self’’ components and ultimately the development of a systemicinflammatory disorder. For this mechanism to operate lung disease would need to precederheumatoid arthritis. Most reports suggest that this is the case. DESPAUX et al. [7] described froman extensive literature review that 90% of 289 reports published since 1928 document respiratory symptoms prior to articular symptoms. While this study combines old reports with variablediagnostic criteria for both rheumatoid arthritis as well as bronchiectasis, in an era beforecomputed tomography (CT) imaging, the temporal sequence is in fact corroborated in severalindividual and more recent studies [4, 5, 54]. Even in newly diagnosed rheumatoid arthritispresent for ,1 year, with normal chest radiographs and normal respiratory function tests, 58% of

patients were found to have HRCT evidence of bronchiectasis. This study demonstratesestablished bronchiectasis, albeit subclinical, by the time of a formal diagnosis of rheumatoidarthritis [59]. However, since the bronchiectasis was subclinical, sufficient antigenic stimulation by bacterial infection seems unlikely.

Bronchiectasis is caused by similar immunological processes or by immunosuppression due to rheumatoid arthritis or its treatments

HRCT has made it clear that airway disease is common in rheumatoid arthritis ( fig. 1). Follicularbronchiolitis is due to lymphoid aggregates, with or without germinal centres, which lie in the wall

of bronchioles and sometimes compress their lumens. This appears as centrilolobular nodules,peribronchial nodules and patches of ground-glass shadowing [60]. Airway wall thickening(indicating bronchitis without dilatation) and bronchiectasis (fig. 1a and b) are both morecommon in patients than matched controls [61].

There is a recognised association of rheumatoid arthritis and obliterative bronchiolitis, also known as‘‘constrictive bronchiolitis’’, in which bronchioles are destroyed and replaced by scar tissue (fig. 1c).

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I L S O N



Several associations have been observed with obliterative bronchiolitis outside of the well-knownassociation with tissue rejection in heart and lung transplantation. Drug treatment, especially withgold and penicillamine, has been implicated in the development of obliterative bronchiolitis [62, 63]but it also occurs in patients who have had neither drug. Obliterative bronchiolitis is well-documented post-infection and although more recognised in children, has been documented withadenovirus, measles, influenza and Mycoplasma [64–69]. Not only could such an outcome easily gounnoticed until later in life, but this could represent a plausible mechanism for the later developmentof formal bronchiectasis or rheumatoid arthritis. Early toxin exposure might also account forobliterative bronchiolitis and later bronchiectasis or rheumatoid arthritis in a similar step-wise

mechanism [70]. Certain human leukocyte antigens (HLA) have been associated with obliterativebronchiolitis, including the presence of HLA-DR1 in obliterative bronchiolitis with rheumatoidarthritis, while a large population fail to have an identifiable cause [71–73]. Bacterial infection may complicate the picture by itself provoking inflammation in the lung and causing damage to the airway wall, as well as exciting rheumatoid arthritis-driven inflammatory processes. Mosaic perfusion andgas trapping are present on HRCT. In the context of the above, patients complain of progressivebreathlessness, develop irreversible airflow obstruction and subsequently carry a poor prognosis withdeath due to respiratory failure [74, 75].

It is interesting to speculate whether these different manifestations of airway disease in rheumatoidarthritis are a single inflammatory process affecting different parts of the bronchial tree, or whetherthey are discrete inflammatory conditions. In favour of the former suggestion, all manifestationsdescribed previously can be seen in the HRCT scan of some patients. However, it is usually necessary to postulate that constrictive obliterative bronchiolitis has been preceded by exudative bronchiolitis,rather than being able to demonstrate this by sequential radiology. However, bronchiectasis coulddevelop in the context of additional local structural damage caused by bacterial infection as aconsequence of functional immunosuppression. DEVOUASSOUX et al. [75] report a study of 25

a) b)

c)

Figure 1. High-resolution computed tomography.

a) Mild tubular bronchiectasis in both lower lobes,

together with mosaic perfusion, in a patient withrheumatoid arthritis. b) Tree-in-bud exudative

bronchiolitis is widespread in both lower lobes of a

patient with rheumatoid arthritis. Small airways having

thickened walls and plugged with mucus are seen asmultiple white dots. c) Severe bilateral lower lobe

bronchiectasis in a patient with poor lung perfusion

due to a constrictive obliterative bronchiolitis.

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U N I T Y



patients with rheumatoid arthritis and obliterative bronchiolitis and demonstrate HRCT evidence of bronchiectasis in 44% of the cohort. All patients were breathless and bronchorrhoea was present in44%. They go on to report that in a follow-up of approximately 4 years, treatment was poorly effective, chronic respiratory failure occurred in 40% and death in four patients.

Rheumatoid arthritis itself is associated with increased morbidity and specifically an increased risk of infection when compared with the general population [76–78]. In a predisposed individual,

regular infection with poor immunological clearance of microbes could subsequently lead toformation of bronchiectasis. In contrast to the reports described previously, SHADICK et al. [2]describes 23 patients with rheumatoid arthritis and bronchiectasis, in whom 18 (78%) patientshad rheumatoid arthritis symptoms prior to the diagnosis of bronchiectasis. These patients had amean duration of arthritic symptoms of 25 years prior to bronchiectasis, 17 out of 18 patients hadused corticosteroids and respiratory symptoms were present for an average of 4.3 years prior tothe formal diagnosis of bronchiectasis. When compared with the five patients who describedbronchiectasis before rheumatoid arthritis, those with late bronchiectasis used more disease-modifying agents, had more severe joint disease, were more likely to have rheumatoid nodules andcarried a greater morbidity. This would support the idea that advanced rheumatoid arthritis

disease and increasingly immunosuppressive medications might contribute to the development of ‘‘secondary’’ bronchiectasis as a late complication of rheumatoid arthritis.

Methotrexate forms part of many rheumatoid arthritis treatment regimens and despite early clinical impressions, probably does not significantly increase the infection risk in patients withpoorly controlled rheumatoid arthritis [79–81]. This may be because the immunosuppressivenature of unchecked inflammation in rheumatoid arthritis in the absence of methotrexateis greater than that conferred by methotrexate itself. However, long-term corticosteroids,cyclophosphamide and azathioprine certainly do lower the threshold for opportunistic infectionand with the emergence of biological agents such as anti-TNF, the complication of seriousinfection and ensuing bronchiectasis becomes more likely [82]. In patients with recurrent

infections on rheumatoid arthritis-treatments it is difficult to define the nature of any immuneparesis, and where specific functional defects are demonstrated it is difficult to ascribe them to thedisease or the therapy that has been prescribed. Gold has been associated with functional antibody defects, but in a study of rheumatoid arthritis patients with and without bronchiectasis, evidenceof antibody deficiency was apparent in those with bronchiectasis as well as those without, andindependent of any co-incident gold therapy [83]. Other reports of late bronchiectasis may havecase-specific explanations, where resistant pathogens, abnormal airways and/or impaired clearancelead to unchecked infection and inflammation and usually localised bronchiectasis [84].

Other diagnoses or comorbid conditions that drive the development of

rheumatoid arthritis and bronchiectasis

In most cases today, a clear diagnosis of rheumatoid arthritis and bronchiectasis can be made thatis based upon the history, clinical features and immunology profile. However, in older studies it isworth noting that either the diagnosis of rheumatoid arthritis may be incorrect, or there may besignificant comorbid conditions that drive the disease phenotype. For example, the finding of greater numbers of abnormal Schirmer’s tests (test of tear production) by MCMAHON et al. [54] ina case-controlled study of 32 patients with rheumatoid arthritis and bronchiectasis whencompared with rheumatoid arthritis without bronchiectasis did increase the possibility thatSjogren’s syndrome was involved in the pathogenesis of one or both conditions, possibly by

affecting mucociliary clearance in the lung. However, this finding was not reproduced by MCDONAGH et al. [52], and KELLY and GARDINER et al. [53] who found no significant difference inabnormal tear production in their rheumatoid arthritis patients with bronchiectasis (six out of 10patients) compared with those without bronchiectasis (18 out of 30 patients).

The cystic fibrosis transmembrane conducatance regulator (CFTR) mutation DF508 present incystic fibrosis (CF) has been implicated through a study of a French cohort that has demonstrated

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its increased presence in rheumatoid arthritis with bronchiectasis [85]. In this study, four (15.4%)out of 26 Caucasians with a median age of 59 years with rheumatoid arthritis and bronchiectasiscarried the heterozygote genotype compared with none from 29 consecutive rheumatoid arthritispatients without bronchiectasis, and none from 29 patients with diffuse bronchiectasis. This is astriking difference when noted in the context of a 2.8% allelic frequency in the general CaucasianEuropean population. In addition, those with the mutation demonstrated more frequent sinusitis,lower nasal potential differences and a trend towards more severe lower respiratory tract disease,

while there was no relationship to the severity of articular features.

HLA associations are well characterised for rheumatoid arthritis and the HLA-DRB1 gene locusfrom the DR4 ‘‘family’’ is perhaps the most closely associated susceptibility locus implicated inrheumatoid arthritis [86]. In a large case-controlled study of patients’ HLA associations in a UKcohort, HILLARBY et al. [87] demonstrated the predicted DR4 association in 79% of rheumatoidarthritis alone patients but no pattern of DR4 subtypes in those with rheumatoid arthritis andadditional respiratory features, including pulmonary fibrosis and bronchiectasis. However, therewas a significant association of rheumatoid arthritis and bronchiectasis with DQB1*0601,DQB1*0301, DQB1*0201 and DQA1*0501 when compared with rheumatoid arthritis alone. The

group of patients with bronchiectasis in a separate prospective HRCT study of 68 consecutiverheumatoid arthritis patients showed a low prevalence of DQA1*0501 when compared with therheumatoid arthritis group without bronchiectasis [6].

Immune dysregulation is seen in both bronchiectasis and rheumatoid arthritis, and a shared defectin both rheumatoid arthritis and bronchiectasis may impact upon the shape of the final diseasephenotype. Common variable immunodeficiency (CVID) is the most common primary immunodeficiency and is frequently associated with both respiratory tract infections andautoimmune conditions including rheumatoid arthritis [88]. Defective antibody production hasbeen recognised in rheumatoid arthritis and with rheumatoid arthritis treatments. A UK study of 80 patients was carried out and comprised of 20 patients with rheumatoid arthritis and

bronchiectasis, 20 patients with each disease separately and 20 healthy matched controls. Threeout of 20 from the rheumatoid arthritis-bronchiectasis group demonstrated an impaired antibody response post-immunisation, two out of 20 rheumatoid arthritis alone patients showed a poorresponse (both groups of patients contained individuals on gold therapy) and the control groupdemonstrated neither. Immunological defects, when investigated, are likely to be more commonthan is currently believed and may play important roles as co-factors in the developingbronchiectasis [89].

Yellow nail syndrome (YNS) is a heterogeneous disorder that includes bronchiectasis and has beenassociated with rheumatoid arthritis-drug therapy, particularly penicillamine. YNS does occur in

rheumatoid arthritis and other autoimmune diseases independent of drug therapy and itsaetiology remains unclear [90, 91]. Abnormal T-cell responses that are thought to drive disease inYNS may similarly drive a specific phenotype in the presence of rheumatoid arthritis and act as aco-factor in development of bronchiectasis.

Management of bronchiectasis in the presence of rheumatoid arthritis

There are no specific features in the management of bronchiectasis associated with rheumatoidarthritis. We have not identified any patients requiring antibody replacement in our own group of rheumatoid arthritis-bronchiectasis patients, but it would be reasonable to measure total antibody levels and specific antibody responses to polysaccharide (pneumococcal and Haemophilus influenzae type b and protein (tetanus)). Some patients have progressive obliterative small airwaysdisease. Our own experience is that there is a poor response in these patients to increasingimmunosuppression, and this approach to treatment creates more problems by making infectionsworse. Once the patient is established by the rheumatologist on a regimen that may includemethotrexate, we have adopted the strategy of trying to reduce the level of bronchial infection by using antibiotic prophylaxis, including the ketolide antibiotic azithromycin as a putative

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immunomodulator [92], and treating exacerbations aggressively. We hypothesise that avoiding theantigenic stimulation of bacterial infections may reduce the inflammatory processes causingobliterative bronchiolitis.

Prognosis

The presence of bronchiectasis with rheumatoid arthritis appears to carry a significantly worse

prognosis, although only one report examines mortality and morbidity in this specific context.SWINSON et al. [93] studied a UK cohort of 32 rheumatoid arthritis patients with bronchiectasisalongside matched controls with either rheumatoid arthritis alone or bronchiectasis alone. They found the mortality in the group with both diseases to be considerably higher, with a standardisedmortality ratio five times and 2.4 times greater than that of the rheumatoid arthritis alone andbronchiectasis alone groups, respectively. The groups shared similar scores of physical activity andof radiological destruction (Larsen score). While several parameters carried high relative risks of mortality including grip strength and presence of rheumatoid nodules, the finding of a raisedwhite cell count and the presence of circulating immune complexes carried the highest relativerisks, the latter being the only one which demonstrated confidence intervals outside parity (relative

risk 4.5, 95% CI 1.4–13.9). The 5-year survival rate in the combined rheumatoid arthritis-bronchiectasis group can be calculated at 69%. Finally, it is interesting to note that those in thecombined disease group did have a lower baseline forced expiratory volume in 1 s (FEV1), as wellas lower forced vital capacity (FVC) and fewer patients with signs of reversibility. Airflow obstruction in the presence of lung restriction has been identified in one large bronchiectasis study as a risk factor for mortality. In this study, carried out over 13 years, 29.7% of patients withbronchiectasis of many different aetiologies died [94]. In contrast, MCMAHON et al. [54] reportedno significant effect of bronchiectasis on the activity and outcome measures of arthritis whencompared with those with rheumatoid arthritis alone.


The study of the association of Sjogren’s syndrome and bronchiectasis has been made moredifficult by: the presence of primary, secondary and mixed syndromes; serological overlap withsystemic lupus erythematosus (SLE; in particular, Sjogren syndrome-related antigen A) and alsosystemic sclerosis; and the inconsistencies in the literature about how the diagnosis of bronchiectasis was made. The diagnosis of Sjogren’s syndrome includes the presence of dry eyesand dry mouth for 3 months, a positive Schirmer’s test, anti-Ro and anti-La autoantibodies and aminor salivary gland biopsy demonstrating a focus score .1. While the use of this definition wasnot clear across all studies, an international consensus was obtained to rectify the differences [95].

Clinically significant bronchiectasis is uncommon and so most information on the prevalence of bronchiectasis in Sjogren’s syndrome necessarily comes from imaging studies of patients withrespiratory symptoms or from studies in those who are asymptomatic. Bronchiectasis is variably reported in such studies ranging from ,10% to 46% [13–16]. In a study of 24 German patientswith primary Sjogren’s syndrome (excluding smokers and those with other autoimmune disease orother unrelated bronchopulmonary disorders), 19 were found to have HRCT abnormalities and 11of these bronchiectatic changes (46% of all patients) [14]. These changes were more central,predominantly lower lobe, bilateral in eight cases and unilateral in three cases. The precisesymptoms of these patients are not given but the cohort comprised of patients referred forinvestigation over a 10-year period to a tertiary referral centre.

The aetiology of Sjogren’s syndrome is unknown but viral infection is implicated, includ-ing Epstein–Barr virus (EBV), cytomegalovirus and retroviruses such as HIV and humanT-lymphocyte virus, with good evidence from animal studies [96]. Both B- and T-cells arerecognised to infiltrate exocrine glands but the pathogenesis is likely to involve a complex interplay of glandular epithelial and endothelial cells, dendritic cells and B- and T-cells in the context of anenvironmental insult in a predisposed individual [97]. Hydration of the airways may be impaired

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together with inspissations of secretions as a result of atrophied respiratory tract mucus glands.Bronchiectasis is proposed to develop subsequently due to recurrent bacterial infections which arepredisposed to by impaired mucociliary clearance. Neutrophilic inflammation provoked by infection leads to thickened dilated lower airways and eventually bronchial wall destruction.Amyloid has been recognised in Sjogren’s syndrome and may be implicated in the development of bronchiectasis with its presence confirmed in peribronchial walls, as well as the interstitium [98].

Management of bronchiectasis associated with Sjogren’s syndrome

There are no clinical studies reported in the literature. In our own practice we have attempted toimprove mucus clearance by nebulising normal saline regularly several times per day andemphasising to patients the importance of physiotherapy. Recently we have begun to nebulise 7%hypertonic saline which has an osmotic effect, with success in individual cases. Optimal antibioticmanagement of lower respiratory tract infections may shorten the length of infective exacerbationsand so reduce airway wall damage.

Systemic lupus erythematosusThe first reports of bronchiectasis in SLE emerged in the early 1960s with the use of bronchogramsand pulmonary function tests [99–101]. With the advent of CT imaging, there has been a greaterunderstanding of the radiological abnormalities in SLE. However, there remains some uncertainty about the significance of the reported abnormalities and the prevalence of clinically significantbronchiectasis. FENLON et al. [17] prospectively studied 34 patients with SLE with HRCT dataalongside various clinical and lung function data. Of note, they found seven (21%) patients withbronchiectasis on HRCT, second only to interstitial lung disease (ILD) (11 patients), mediastinalor axillary lymphadenopathy (six patients) and pleuropericardial abnormalities (five patients).However, while the presence of HRCT abnormalities was high they found no correlation withsymptoms or disease activity, and none of the patients had recurrent respiratory infections. In aseparate cross-sectional study of 60 Norwegian adults of childhood-onset SLE, any HRCTabnormality was found in only five patients and in just one (,2%) was there radiological evidenceof bronchiectasis; none had clinical evidence of bronchiectasis [18]. These patients had a medianduration of 11 years of disease by the time of cross-sectional imaging. In contrast, BANKIER et al.[19] reported a much higher frequency of CT abnormalities with 17 out of 48 patients with SLEshowing abnormalities (45 of whom had normal chest radiographs). They went on to show correlation of extent of disease radiologically with duration of clinical history (r50.93), gastransfer (r50.8) and ratio of FEV1/FVC (r50.77). However, once again there was poor correlationof bronchiectasis on CT scans and clinical symptoms of the disease. Lung fibrosis may causetraction bronchiectasis and it is not clear in reports whether bronchiectasis is present in parts of the lung not affected by fibrosis.

As with other systemic diseases, it has been suggested that confounding factors might explain theassociation of bronchiectasis with SLE, including the increased risk of infection associated with amulti-system disease and use of immunosuppressive treatments to control the disease. Mannose-binding lectins (MBL) have been suggested to play a role in SLE in a report of two patients withSLE who went on to develop CVID [102]. The infrequent MBL haplotype 4Q-57Glu was presentin both, while the haplotype 4P-57Glu in the second case was associated with recurrent respiratory infections, bronchiectasis and low circulating levels of MBL. This report raises the possibility of

MBL polymorphisms in the development of autoimmune disease and significant infections whichcause bronchiectasis.

The clinical features of bronchiectasis in SLE are not described in the literature. However, it isapparent that the most common pulmonary complications are infection and vascular events [103].While the reported frequency of clinical bronchiectasis is low, as described previously, there may be under-diagnosis of post-infective bronchiectasis in patients who have not had HRCT examination.

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Respiratory function tests frequently demonstrate reduced spirometry (typically subclinical), reducedgas diffusion and, depending on severity of disease, decreased lung capacity. These changes appear tobe independent of cigarette smoking [103–105].

HRCT features reported in SLE include pleuritis with or without pleural effusion, acute interstitialpneumonia and acute pulmonary haemorrhage and thrombosis [17, 106]. Morbidity andmortality in SLE are associated with infection and vascular complications [107, 108]. There is

greater mortality in the first 5 years, partly linked to the use of immunosuppressive therapy inaggressive SLE disease and the subsequent complications of infection surrounding this.

Ankylosing spondylitis

There are several pulmonary manifestations of ankylosing spondylitis which include apicalfibrobullous disease, secondary infection, chest wall restriction, obstructive sleep apnoea,spontaneous pneumothorax and bronchiectasis [109]. A typical course is the development of chronic bi-apical fibrobullous areas with nodules that eventually coalesce to form cysts, cavitiesand bronchiectasis, and later superadded infection with Aspergillus and environmental Myco-

bacteria species may occur. Abnormalities evident on HRCT in those either asymptomatic or withearly disease are well documented with frequencies of all abnormalities in the region of 40% to80% [20–22, 110]. However, little is published regarding bronchiectasis specifically. HRCTevidence of bronchiectasis has been found in 7–23% of ankylosing spondylitis patients in thelargest cohort studies performed to date [17, 20, 21–24]; in most studies, patients do not reportsymptoms of bronchiectasis. Traction bronchiectasis is the most likely explanation in this contextcaused by pleuropulmonary fibrosis. FENLON et al. [111] reported a total of six (23%) cases of bronchiectasis from their prospective cohort study of 26 patients with ankylosing spondylitis froman out-patient setting in Ireland, of which four were primary bronchiectasis and two had tractionbronchiectasis. The four with primary bronchiectasis consisted of three patients with significant

smoking histories, two each with disease in the upper and lower lobes and only one withsymptoms of cough and breathlessness. The latter patient with bronchiectasis had ankylosingspondylitis for significantly longer duration of 28 years, and had an abnormal plain chestradiograph (demonstrating upper lobe bronchiectasis) with restrictive respiratory function tests.Three out of four patients with bronchiectasis in a separate study from Brazil were also currentsmokers, although this population with several radiological abnormalities may have had otherinfective causes [23].

Tracheobronchomegaly or Mounier–Kuhn syndrome, which is due to a congenital cartilageabnormality, has also been reported with ankylosing spondylitis and this mechanism may influence the development of bronchiectasis in some cases [112]. HLA-B27 does not appear to

correlate with general HRCT abnormalities where this has been assessed, and while it is possiblethat ankylosing spondylitis disease severity correlates indirectly with respiratory abnormalities ingeneral, there are too few cases with bronchiectasis to assess any relationship with this specifically [23, 113, 114]. There is insufficient data to comment on the timing of bronchiectasis comparedwith the development of ankylosing spondylitis, although it appears that the majority of thosefound to have bronchiectasis are asymptomatic with incidental findings on imaging only [20–24,110, 115]. Ankylosing spondylitis mortality is usually caused by non-respiratory illnesses such ascardiovascular disease, renal failure and amyloid and through complications of treatment, andonly occasionally through respiratory disease [116–118].

Scleroderma/systemic sclerosis

Lung involvement in scleroderma or systemic sclerosis is very common. HRCT has played animportant role in better characterising and following up abnormalities, and disease has also beenwell documented by post mortem examination with the identification of pulmonary disease insystemic sclerosis in 80% of one cohort [25–27]. The findings of an ILD, typically a nonspecific

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interstitial pneumonia (NSIP) pattern and pulmonary hypertension, are quite common on HRCT.Any honeycombing is usually mild and localised and the more typical pattern is the near-confluentground-glass opacification, fine reticular markings and associated traction bronchiectasis. Primary bronchiectasis is uncommon [28, 29], as are reports of clinically significant disease.

In one of the larger studies of systemic sclerosis patients alone, ANDONOPOULOS et al. [29]investigated 22 patients with a full history, respiratory function tests, blood tests and HRCT

imaging. Cylindrical bronchiectasis was evident in 13 (59%) out of 22 patients and was morecommon in diffuse rather than limited systemic sclerosis disease, although this finding fell shortof statistical significance and did not correlate with gas transfer, ground-glass opacification orwith the patient’s duration of illness. In another single case report of clinically significantbronchiectasis, there were other potential causes including Sicca syndrome and immunosup-pressant treatment [119].

Relapsing polychondritis

The tracheobronchial tree is affected and typically leads to thickened and sometimes narrowed

airways, impaired clearance and the development of airway infection and inflammation. Lowerrespiratory tract symptoms and significant disease developed after the initial diagnosis of relapsingpolychondritis in an early and one of the largest prospective studies of 23 patients with relapsingpolychondritis [30]. However, this was not the case in the only other smaller prospective series20 years later where in six out of nine patients the respiratory symptoms were the presentingsymptoms of relapsing polychondritis [31]. Cohort studies since 1966 report a prevalence of respiratory symptoms in up to 50% of those with relapsing polychondritis, although given thenature and time of these studies, accurate prevalence of bronchiectasis is not possible to estimate.A small number of cohort studies have analysed the natural history, morbidity and mortality of patients with relapsing polychondritis. Respiratory infection appears to play a significant part.

Bronchiectasis is not defined by today’s standards of HRCT imaging given that these studies werecarried out between 1966 and 1986. However, it can be implied that together with vasculitis andvalvular heart disease, respiratory infection carries a worse prognosis [30, 32, 33]. MICHET et al.[32] describe their single-centre experience of 112 patients in the US in which they identifiedrespiratory infection as one of the leading causes of death alongside vasculitis and cancer. Of further interest is that only 10% of deaths were directly attributed to airway involvement of thedisease, that anaemia was a significant poor prognostic marker and that the use of corticosteroidsdid not impact on survival.

BEHAR et al. [34] analysed past records of a cohort of 160 patients collected over 10 years from tworeferral centres and scrutinised records from 15 patients who had undergone any thoracic CT

imaging. They identified increased attenuation in the tracheal walls of all 15 patients (withnarrowing in one third of these patients), and also in the bronchial walls of 11 patients (73% of those scanned). Of the 11 patients who had complete lung view imaging, three were found to havebronchiectasis (two upper lobe, one diffuse), two demonstrated no significant airway stenoses andone showed widespread tracheal and bronchial stenoses. 12 (83%) out of 15 patients demonstratedthickened airway walls.

Mixed connective tissue disease

Mixed connective tissue disease (MCTD) is a distinct clinicopathological entity with uniquepositive antibodies against ribonucleoprotein that shares several clinical and radiological featureswith SLE, systemic sclerosis and polymyositis/dermatomyositis (PM/DM). The frequency of respiratory manifestations in MCTD is reported to be between 20% and 80%, more commonly thehigher end of this range, although the reports are typically based upon radiological findings ratherthan clinical significance [35, 120, 121]. The prevalence of bronchiectasis is not available in theseolder studies, once again because of the absence of HRCT. MCTD is not usually associated with

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primary bronchiectasis, rather with traction bronchiectasis associated with architectural distor-tions and the interstitial pneumonia patterns more commonly seen in this disorder [36, 37].KOZUKA et al. [37] analysed the abnormal HRCT imaging of 41 patients with confirmed MCTDand characterised the radiological abnormalities that were observed. They identified 18 patientswith traction bronchiectasis. Primary bronchiectasis was observed in five (12%) out of 41 patients,although no clinical features were reported in this study to assess the significance of this.

Polymyositis/dermatomyositis

PM/DM is typically associated with ILD with a strong correlation with anti-Jo1 antibodies, mostcommonly an NSIP pattern and also an organising pneumonia [38, 39]. Primary bronchiectasis isnot reported and traction bronchiectasis is rarely reported, especially given that honeycombing isan infrequent finding in contrast to ground-glass opacification and patchy consolidation [38–40].

Bronchiectasis and vasculitis

It has long been recognised that immune complexes and autoantibodies can accompany bronchialinfection [41, 122–125]. ABRAMOWSKY and SWINEHART [123] demonstrated renal failure associatedwith immune complexes in patients with CF and immune complex-mediated injury was proposedin CF patients who presented with purpuric lesions late in their disease course [124]. Immunecomplexes adhere to the endothelium through binding with the C1q component of complementcausing vasculitis and/or the complexes interfere with the intended complement-mediatedclearance of pathogens.

The vasculitic process may be localised or involve many systems with increasing severity. Theextent of disease may be such as to require aggressive immunosuppressive therapy withcorticosteroids and cyclophosphamide to control the vasculitis, alongside continued antimicrobialtreatment for concomitant bacterial infection [126]. Evidence of immune-mediated injury andvasculitis has been demonstrated in the context of H. influenzae and Staphylococcus aureus , as wellas Pseudomonas aeruginosa [2, 42, 125].

Antineutrophil cytoplasmic antibodies (ANCA) form an important component of vasculitides of which classical ANCA (c-ANCA) against the antigen proteinase-3 and perinuclear ANCA(p-ANCA) against myeloperoxidase make up the major pathogenic types [43]. Of the primary vaculitides, granulomatosis with polyangiitis (Wegener’s) with associated c-ANCA antibodies andmicroscopic polyangiitis (MPA) with myeloperoxidase antibodies have been most linked withbronchiectasis. A chronic pulmonary illness typically predates the development of ANCA-

associated disease in various reports and although other ANCA may exist their roles may be morespecific [41, 44–46]. In a retrospective cohort study of 26 patients with MPA in Japan, nine (35%)were diagnosed with bronchiectasis, four of whom had bronchiectatic symptoms prior to thediagnosis of MPA [45]. The precise role and timing of the development of autoantibodies to self-components remains unclear. FORDE et al. [47] analysed sera from a large number of patients witha wide variety of inflammatory and infective disorders in order to investigate any association of autoantibodies with acute and chronic infection. They concluded that antibodies to neutrophiliccytoplasmic components were predominantly associated with chronic bacterial infection, whileantibodies to monocyte cytoplasmic components were predominantly associated with chronicgranulomatous disorders such as sarcoidosis. The implication was that persistent stimulation of

phagocytic cell components by bacterial infection drives the formation of autoantibodies to thosecomponents and a pathological humoral response.

More recently, studies have begun to confirm the temporal relationship of immune-complex activity with infection. MAHADEVA et al. [48] identified and characterised a new antigenbactericidal/permeability-increasing protein (BPI)-ANCA in the context of Pseudomonas infection.They went on to identify this in several patient groups including those with CF and non-CF

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bronchiectasis, inflammatory bowel disease and renal failure [49]. Other groups explored itsbehaviour in the context of Pseudomonas and proposed that high levels of BPI-ANCA correlatedwith chronic Pseudomonas infection and poorer prognosis [46, 127, 128]. Of note, BPI binds withhigh affinity to lipopolysaccharide (LPS) on Gram-negative bacteria, and the presence of highlevels of circulating antibodies to BPI may interfere with clearance of LPS bacteria giving rise toconcomitant severe infection.

There are several other rare primary immunodeficiencies that are associated with bronchiectasisand vasculitis about which little is known. For example, an X-linked lymphoproliferative disorderlinked to a specific T-cell defect in EBV immunity that is associated with multi-system vasculitis,bronchiectasis, respiratory failure and death [129] and an, as yet, poorly defined syndromeconsisting of childhood dermatitis, profoundly elevated immunoglobulin E, severe pneumonia(and subsequent bronchiectasis) and multiple central neurological abnormalities [130].

The use of immunosuppressive agents and bronchiectasis

There is an increasing use of immunomodulatory or immunosuppressive therapy that is proving

successful in modifying autoimmune disease processes [82]. However, their availability has raisedfresh concerns, mainly surrounding opportunistic infection and cancer [131–135]. In theautoimmune diseases discussed herein, those drugs used frequently include steroid-sparing agentssuch as azathioprine and methotrexate, alternative potent immunosuppressive drugs such asleflunomide and cyclophosphamide, biological agents that include anti-TNF agents (etanercept,infliximab and adalimumab), anti-CD20 molecules (rituximab), interleukin (IL)-6 receptorantagonists (tocizilimab) and co-stimulatory inhibitor molecule (abatacept).

Reactivation of tuberculosis (TB) is a recognised risk of the use of anti-TNF therapy and theBritish Thoracic Society and others have issued guidelines for their use in those at risk of TBreactivation [136, 137]. TB and nontuberculous Mycobacteria [138] are pathogens that can bothcause bronchiectasis and infect patients with existing bronchiectasis. Care must be taken to stratify the risk of reactivation following immunosuppressive therapies, and one should be aware thattraditionally non-pathogenic strains can emerge as fatal infections [139]. Evidence for latent TBinfection should be sought with the use of a detailed history, chest radiograph or CT, tuberculinskin testing and interferon-c release assays (IGRA). IGRAs are now well established and should beused to ‘‘risk-stratify’’ in the context of anti-TNF therapy. While in theory latent viruses includingherpes zoster and EBV, fungus, opportunistic bacteria and parasites are all more likely to re-emerge with immunosuppressive therapy, this has not been a consistent finding [140–145].

There may be a gradation of risks within this group of agents. Anti-CD20 therapy in the form of

rituximab may generally be considered less aggressive. CD20 is expressed by haematopoieticprogenitor cells and newly differentiated plasma cells, and while reactivation of latent virus is welldocumented, infection with other bacteria or parasites or TB is infrequently reported [146, 147].Safety and long-term data are still emerging with tocilizumab, an IL-6 receptor antagonist foundto be effective in rheumatoid arthritis and still being investigated for SLE [147–150]. To date, nosurprising opportunistic infection data has emerged and meta-analyses have placed a figure of approximately six additional infections per 100 patient-years; those infections are mostly termed‘‘pneumonia’’ [149, 151]. Abatacept, a newer co-stimulatory modulator that interferes with T-cellactivation may not share the same documented risks of TB reactivation and may prove to be bettertolerated than anti-TNF therapies, although longer term safety data on this drug is still emerging

[152–155].

In general, physicians using these agents must be diligent and counsel patients about the risks of infections, particularly if patients already have susceptibility to infection due to concomitantbronchiectasis. In this case the patient should be co-managed with a respiratory physician, sputumshould be screened for Mycobacteria sp. and other opportunistic pathogens, the patient shouldhave an antibiotic management plan if infective exacerbations develop, and antibiotic prophylaxis

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should be considered if infective exacerbations become frequent. These agents often providemarked improvement in the patient’s control of their autoimmune disease, which means thatwhen the agents are used in bronchiectasis patients with associated autoimmune disease, treatmentof chronic bronchial infection and infective exacerbations of bronchiectasis should be intensifiedto allow the agent to be continued when this is deemed to be safe. Good communication betweenthe rheumatologist and pulmonologist is essential.


None declared.

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Chapter 14

Antibiotic treatment

strategies in adults

with bronchiectasisC.S. Haworth

Summary Antibiotics play a crucial role in the management of patients with bronchiectasis by disrupting the vicious circle of infection,inflammation and airway damage central to the pathophysiol-ogy of the condition. Antibiotic use in patients with bron-chiectasis can be divided into exacerbation treatment, chronicsuppressive treatment and eradication treatment.

Antibiotics administered during exacerbations are known

to reduce serum C-reactive protein concentrations, sputum volume and bacterial density, as well as ameliorate symptoms.Clinical experience suggests that better outcomes are seen with higher dose/longer duration regimens.

The prescription of long-term oral antibiotics should beconsidered in patients requiring exacerbation treatment at leastthree times per year. As patients chronically infected withPseudomonas aeruginosa tend to have a faster rate of lung function decline, more admissions to hospital and a worsequality of life compared with bronchiectasis patients with othermicroorganisms, nebulised antipseudomonal antibiotics arecommonly prescribed.

Eradication antibiotics should be considered following identification of new growths of P. aeruginosa due to theincreased morbidity associated with chronic infection.

Keywords: Antibiotics, bronchiectasis, exacerbation,intravenous, nebulised, prophylaxis

Correspondence: C.S. Haworth,Cambridge Centre for Lung Infection,Papworth Hospital, Cambridge, CB233RE, UK, [email protected]


B ronchiectasis is a condition characterised by irreversible dilatation of the bronchi [1] resultingfrom changes in the elastic and muscular components of the bronchial wall. COLE [2]

proposed the vicious circle hypothesis in the 1980s to explain the pathogenesis of bronchiectasis.He suggested that an initial insult to the airway leads to bronchial wall inflammation and damage,disordered mucociliary clearance, a predisposition to chronic or recurrent infection and as aresult, further airway damage. Antibiotic use in patients with bronchiectasis can be divided into

2 1 1

C . S .

H A W

O R T H



exacerbation treatment, chronic suppressive treatment and eradication treatment. Treatment of pulmonary diseases related to nontuberculous mycobacteria and fungi will be covered by otherchapters in this issue.

Antibiotic treatment in exacerbations of bronchiectasis

Patients with bronchiectasis may expectorate significant volumes of mucopurulent sputum whenwell. It is therefore important to document stable state symptoms so that exacerbations can beaccurately identified. Failure to do this can result in inappropriate antibiotic treatment.

Acute exacerbations of bronchiectasis are characterised by an increase in cough frequency, sputumvolume, sputum purulence and viscosity. Patients may also complain of chest tightness, wheezeand breathlessness. Other common features include streaky haemoptysis, chest discomfort andtemperatures. Symptoms usually progress over days, but patients can experience a more insidiousdecline over weeks or months.

There are no randomised placebo-controlled trials evaluating the effect of antibiotic treatment

during exacerbations of bronchiectasis. However, antibiotics are known to reduce serumC-reactive protein, sputum inflammatory indices, sputum volume, sputum purulence andbacterial density, as well as ameliorate symptoms [3–8].

The published literature evaluating antibiotic treatment during exacerbations of bronchiectasis isheterogeneous in terms of the class of antibiotic studied, the route of administration and thesputum microbiology of the participants. However, important management principals emerge:high doses of an antibiotic are often more effective than lower doses of the same antibiotic [3];patients with purulent sputum after antibiotic treatment have a shorter time to next exacerbationcompared with patients with mucoid sputum [3]; sputum culture sensitivity results do notnecessarily predict clinical response to antibiotic treatment [9]; short courses of oral antibiotics

prescribed during acute exacerbations reduce airway inflammatory indices to pre-exacerbationlevels, but chronic low-grade inflammation persists [4]; and clinical improvement may not beassociated with significant increases in spirometry [7, 8, 10].

Initial treatment usually involves a course of oral antibiotics unless the patient is sufficiently unwell to require intravenous treatment. The optimal dose and duration of antibiotic treatment tomanage bronchiectasis exacerbations is currently undefined. Clinical experience suggests thatbetter outcomes are seen with higher dose/longer duration regimens, which presumably reflectsthe difficulty of achieving adequate antibiotic concentrations within the lumen of bronchiectaticairways, particularly in the context of chronic infection where bacteria are often resistant and

protected by biofilms. Expert consensus is that bronchiectasis exacerbations should be treated with14 days of antibiotics [11]. A sputum sample should be sent for culture before starting empiricalantibiotic treatment and the results can influence changes in treatment if the patient is notresponding.

Oral antibiotic treatment for exacerbations of bronchiectasis

Oral antibiotic choices should be guided, where possible, by previous sputum microbiology andsuggestions for treatment are outlined in table 1. Empirical treatment may be with amoxicillin500 mg t.i.d. or co-amoxiclav 625 mg t.i.d. in patients in whom b-lactamase-producingorganisms are suspected. Doxycycline 100 mg b.i.d. is an alternative choice in the context of penicillin allergy and ciprofloxacin 750 mg b.i.d. should be prescribed if Pseudomonas aeruginosa infection is thought to be likely. Patients with a history of methicillin-resistant Staphylococcus aureus (MRSA) infection may be treated with rifampicin 600 mg q.d. and fucidin 500 mg t.i.d.The potential for antibiotic related complications such as Clostridium difficile infection needto be considered when choosing oral or i.v. antibiotic regimens to treat exacerbations of bronchiectasis.

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Intravenous antibiotic treatment for exacerbations of bronchiectasis

Patients with severe exacerbations or exacerbations that fail to resolve with oral antibiotictreatment may require treatment with i.v. antibiotics. This usually involves admission to hospital,but some centres run community-based i.v. antibiotic programmes, which allow patients to haveall, or a proportion, of their treatment at home. This is particularly helpful for younger patientswho have educational commitments or for those that do not want to take time out from work.Patients must demonstrate that they are competent at i.v. drug administration before dischargeand the home environment needs to be appropriate. Most centres recommend that the first dose isadministered in hospital to ensure patients can infuse the antibiotic correctly and to ensure thereare no adverse events. Robust systems need to be in place to monitor drug levels in patientsprescribed aminoglycosides and careful monitoring of renal function is essential in patientsreceiving nephrotoxic medicines.

Antibiotic i.v. administration during bronchiectasis exacerbations can be achieved through use of peripheral cannulas, long lines, peripherally inserted central catheters (PICC) and totally implantable venous access devices (TIVAD) (fig. 1). PICCs and TIVADs are particularly useful inpatients with difficult peripheral access who require frequent courses of i.v. treatment. However,these devices require regular flushing and potential complications include thrombosis andinfection, particularly in higher risk groups such as the elderly and those with a primary or

secondary immunodeficiency.

Antibiotic i.v. choices should be based on previous sputum microbiology results and suggestedregimens are outlined in table 2. Empirical antibiotic treatment may include cefuroxime orceftriaxone, unless patients are thought to be infected with P. aeruginosa . As the efficacy of b-lactam antibiotics is related to the time above the mean inhibitory concentration, once daily antibiotics may be less effective than antibiotics taken three times a day due to the potential

Table 1. Oral antibiotic regimens commonly used to treat acute exacerbations of bronchiectasis in adults#

Organism First line Second line

Streptococcus pneumoniae Amoxicillin 500–1000 mg t.i.d." Clarithromycin 500 mg b.i.d.

Doxycycline 100 mg b.i.d.

Moxifloxacin 400 mg q.d. Trimethoprim 200 mg b.i.d.

Haemophilus influenzae Amoxicillin 500–1000 mg t.i.d." Doxycycline 100 mg b.i.d.

Co-amoxiclav 625 mg t.i.d.Ciprofloxacin 750 mg b.i.d.

Trimethoprim 200 mg b.i.d.

Moraxella catarrhalis Co-amoxiclav 625 mg t.i.d. Doxycycline 100 mg b.i.d.

Ciprofloxacin 750 mg b.i.d.Clarithromycin 500 mg b.i.d.

Staphylococcus aureus Flucloxacillin 500–1000 mg q.i.d." Clarithromycin 500 mg b.i.d.

Doxycycline 100 mg b.i.d.Co-amoxiclav 625 mg t.i.d.


Moxifloxacin 400 mg q.d.MRSA Rifampicin 400–600 mg q.d.+ and

fucidin 500 mg t.i.d.


Doxycycline 100 mg b.i.d.

Linezolid 600 mg b.i.d.Pseudomonas aeruginosa Ciprofloxacin 750 mg b.i.d.

Coliforms Ciprofloxacin 750 mg b.i.d. Co-amoxiclav 625 mg t.i.d.

Stenotrophomonas maltophilia Cotrimoxazole 960 mg b.i.d. Minocycline 100 mg b.i.d.

Achromobacter xylosoxidans Minocycline 100 mg b.i.d.

q.d.: once daily; b.i.d.: twice daily; t.i.d.: three times daily; q.i.d.: four times daily; MRSA: methicillin-resistant

Staphylococcus aureus . #: recommended treatment duration 10–14 days; ": dose according to severity;+: dose according to weight.

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problem of maintaining an ade-quate intraluminal antibiotic con-centration in the context of structural lung damage and biofilmformation.

Antibiotic i.v. treatment in

patients infected withP. aeruginosa

Empirical antibiotic treatment inpatients with P. aeruginosa may include a b-lactam, such as cefta-zidime. Monotherapy may sufficein patients infected with fully sensitive P. aeruginosa , but in thecontext of a resistant organism orchronic infection where patientsare likely to require repeated treat-ment courses in the future, many clinicians advocate dual therapy with an aminoglycoside to reducethe risk of antibiotic resistance, as

well as harnessing the synergistic effects between aminoglycoside and b-lactam antibiotics [12–14].In a study evaluating the effect of i.v. azlocillin + placebo versus i.v. azlocillin + tobramycin inpatients with cystic fibrosis (CF), initial clinical outcomes were comparable, but P. aeruginosa density decreased more and time to next hospitalisation was significantly longer in the groupreceiving dual therapy [15]. These data suggest that dual antibiotic therapy is preferable in thecontext of chronic P. aeruginosa infection and the absence of significant comorbidity (such as renaldysfunction).

Figure 1. Chest radiograph of a male patient with primary ciliarydyskinesia, dextrocardia, severe bilateral bronchiectasis and chronic

Pseudomonas aeruginosa infection who self-administers i.v. anti-

biotics via a totally implantable venous access device at home.

Table 2. Antibiotic i.v. regimens commonly used to treat acute exacerbations of bronchiectasis in adults#


Streptococcus pneumoniae Benzylpenicillin 1.2 g q.i.d. Cefuroxime 1.5 g t.i.d. or

Ceftriaxone 2 g q.d.

Haemophilus influenzae Cefuroxime 1.5 g t.i.d. or

ceftriaxone 2 g q.d.

Piperacillin with

Tazobactam 4.5 g t.i.d.Moraxella catarrhalis Cefuroxime 1.5 g t.i.d. or


Piperacillin with

tazobactam 4.5 g t.i.d.

MRSA Vancomycin" Teicoplanin"

Linezolid 600 mg b.i.d.

Tigecycline 50 mg b.i.d.

Fosfomycin 5 g t.i.d.Pseudomonas aeruginosa Ceftazidime 2 g t.i.d.+ Aztreonam 2 g t.i.d.+

Piperacillin with

tazobactam 4.5 g t.i.d.+

Meropenem 1 g t.i.d.+

Coliforms Cefuroxime 1.5 g t.i.d. or


Piperacillin with

tazobactam 4.5 g t.i.d.Stenotrophomonas maltophilia Cotrimoxazole 1.44 g b.i.d. Tigecycline 50 mg b.i.d.

Achromobacter xylosoxidans Piperacillin with tazobactam 4.5 g t.i.d. Meropenem 1 g t.i.d.

q.d.: once daily; b.i.d.: twice daily; t.i.d.: three times daily; q.i.d.: four times daily; MRSA: methicillin-resistant

Staphylococcus aureus . #: recommended treatment duration 10–14 days; ": dose according to weight and

drug levels; +: dual therapy with gentamicin or tobramycin may be required.

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The most appropriate choice of aminoglycoside remains a matter for debate, but recent reportssuggest that the risk of renal impairment, ototoxicity and vestibular damage is greater withgentamicin than tobramycin [16, 17]. While, once daily versus three times daily tobramycin dosingin children with CF appears to offer equivalent clinical outcomes and reduced renal toxicity [18],the most appropriate dosing regimen has not been established in adults with bronchiectasis.

The role of antibiotic sensitivity testing in patients with bronchiectasis and chronic P. aeruginosa

infection is contentious due to hypermutation and the poor correlation between in vitro antibioticsensitivity test results and clinical outcomes [19, 20]. FOWERAKER et al. [19] studied sputumsamples from patients with CF and found an average of four P. aeruginosa morphotypes persputum sample and three distinct antibiotic sensitivity profiles per morphotype. 48 colonies withvarying antibiotic sensitivity profiles were cultured from one sputum sample and it was noted thatsusceptibility profiles of single P. aeruginosa isolates correlated poorly with pooled cultures (thepooled cultures underestimated levels of antibiotic resistance). FOWERAKER et al. [19] also showedthat sensitivity results from one sputum sample tested in duplicate by eight biomedical scientistswithin one laboratory and by biomedical scientists in seven other laboratories did not correlatewell. These data are supported by the findings of SMITH et al. [21], who showed no correlation

between the susceptibility of P. aeruginosa to ceftazidime or tobramycin and clinical response tothese antibiotics in 77 chronically infected patients with CF. Furthermore, a randomisedcontrolled trial evaluating clinical outcomes, using multiple combination bactericidal testingversus clinician preference, to guide i.v. antibiotic choices to manage CF pulmonary exacerbationsshowed no advantage in using the more sophisticated microbiological tests [22]. Based on theabove evidence, a pragmatic approach is required when choosing antibiotic combinations forpatients with bronchiectasis and chronic P. aeruginosa infection. It is common practice to choosetwo antipseudomonal antibiotics (usually a b-lactam in combination with tobramycin) to whichthe majority of morphotypes are sensitive. An alternative approach involves basing antibioticchoices predominantly on what has worked well for the patient in the past.

Nebulised antibiotic treatment for exacerbations of bronchiectasis

The nebulised route enables delivery of high concentrations of antibiotic to the airways andreduces the likelihood of gastrointestinal adverse events. However, airway inflammation may leadto bronchoconstriction and drug deposition may be limited by sputum plugging.

BILTON et al. [6] tested the effect of adding inhaled tobramycin solution to oral ciprofloxacin fortreatment of bronchiectasis exacerbations in the context of P. aeruginosa infection. The study involved53 adults recruited from 17 study centres in the UK and USA. There was evidence of superiormicrobiological efficacy in patients receiving inhaled tobramycin and ciprofloxacin compared with

those receiving ciprofloxacin alone, but superior clinical efficacy was not demonstrated. Patientstreated with inhaled tobramycin and ciprofloxacin were more likely to experience respiratory adverseevents, in particular wheeze (50% in the inhaled tobramycin group compared with 15% in theplacebo group). Although treatment emergent wheeze was not a significant cause for withdrawal fromthe study, it is probable that it influenced the clinical efficacy outcome data. It is also notable thatpatients with ciprofloxacin resistant strains of P. aeruginosa were excluded from the study and it ispossible that the inclusion of such patients, as would occur in routine clinical practice, may haveresulted in more favourable outcomes in the inhaled tobramycin-treated patients.

Antibiotic prophylaxis in adults with bronchiectasisAntibiotics are commonly prescribed on a long-term basis in patients with bronchiectasis with aview to improving symptoms, decreasing exacerbation rates and optimising quality of life. Themost likely mechanism by which antibiotics achieve these aims is by reducing bacterial load andairway inflammation. The immunomodulatory benefits of long-term macrolide antibiotics arediscussed in a later chapter by SMITH et al. [23].

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Antibiotics used on a long-term basis are usually administered orally or through a nebuliser.However, within the CF population, some centres advocate 3-monthly elective courses of i.v.antibiotics for patients chronically infected with P. aeruginosa [24]. This approach has not beentaken up widely due to concerns about toxicity (particularly renal, vestibular and auditory),psychosocial well-being (disruption to family life, work and education), healthcare costs and thoseconcerns relevant to all forms of antibiotic prophylaxis: increasing bacterial resistance and thecreation of a niche for new organisms (both bacteria and fungi) [25, 26].

Oral antibiotic prophylaxis in adults with bronchiectasis

The evidence base for oral antibiotic prophylaxis in bronchiectasis dates back to the early 1950swhen a number of unrandomised studies were performed [27, 28]. However, these were soonsuperseded by the Medical Research Council study which involved 122 subjects randomised toreceive penicillin, oxytetracycline or placebo [29]. The drugs were provided as indistinguishable0.25 g capsules and patients were asked to take two capsules four times a day on two days eachweek for 1 year. Outcome measures included 24-h sputum volume and the severity of cough,dyspnoea, haemoptysis and disability. Unfortunately no formal statistical analysis was performed.

After 1 year, oxytetracycline treatment was associated with a reduction in sputum volume to 64%of pre-treatment levels and the purulent fraction was reduced by 50%. Treatment withoxytetracycline was also associated with fewer days off work and fewer days confined to bed. Lessmarked changes were evident in patients allocated to the penicillin and placebo groups.Gastrointestinal symptoms were reported by a minority of patients (five on oxytetracycline, threeon penicillin and two on placebo) and one patient in the oxytetracycline and penicillin groupsdiscontinued treatment due to antibiotic intolerance. Unfortunately, sputum microbiology datawere not reported and so it is not possible to make an assessment of whether sensitivity profilesaffected outcomes. Subsequent studies in the 1950s and 1960s provided further support for the useof long-term tetracycline/penicillin based antibiotic regimens in patients with bronchiectasis

[30, 31]. However, the latter study also reported an increase in the isolation of Pseudomonas andProteus species, suggesting that microbial flora of sputum may be altered by long-term antibiotictreatment.

CURRIE et al. [32] performed a randomised placebo-controlled trial evaluating the effect of high-dose amoxicillin in patients with bronchiectasis. 38 subjects were randomised to receiveamoxicillin 3 g b.i.d. or placebo for 32 weeks. Assessment of overall response based on diary carddata showed that a higher proportion of patients improved in the amoxicillin group (11 out of 17)compared with the placebo group (four out of 19). Patients in the amoxicillin group also spentsignificantly less time confined to bed and away from work compared with the placebo group. Thefrequency of exacerbation was similar in the two groups, but the exacerbations were less severe inthe amoxicillin group than before the study was started. There was also a greater reduction inpurulent sputum volume in the amoxicillin group (20% of pre-treatment volume) compared withthe placebo group (88% of pre-treatment volume). One patient in the amoxicillin group withdrew from the study due to the development of rash and one patient from each group withdrew due todiarrhoea. There was a trend towards greater antibiotic resistance in patients treated withamoxicillin. No patients developed C. difficile -related diarrhoea.

In a 16-week open-label study of oral and nebulised amoxicillin involving 10 patients withbronchiectasis and variable sputum microbiology (predominantly Haemophilus influenzae ),treatment was associated with reduced sputum purulence and volume, reduced sputum

inflammatory indices, improvements in lung function and improved patient well-being [33].After cessation of treatment, sputum purulence returned after a median of 2.5 months.

R AYNOR et al. [34] performed a retrospective case note review of 10 patients with bronchiectasisprescribed .90 days of continuous oral ciprofloxacin. Pre-treatment sputum microbiology resultsfrom nine patients showed a variety of organisms including P. aeruginosa (n55), H. influenzae (n53) and Streptococcus pneumoniae (n51). At the end of treatment six patients had sterile sputum

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cultures, of which two had previously grown P. aeruginosa , three H. influenzae and one had nopathogen. In one patient P. aeruginosa was replaced by S. pneumoniae , two patients continued toculture P. aeruginosa (which had become resistant to ciprofloxacin) and S. pneumoniae persisted inone patient. While exacerbation frequency and hospital admissions reduced with treatment, thedevelopment of ciprofloxacin-resistant strains of P. aeruginosa is of concern, particularly as thisfinding coincided with a relapse in symptoms requiring admission to hospital for i.v. antibiotics.

In practice, the prescription of long-term oral antibiotics is considered in patients requiringexacerbation treatment at least three times per year (or in patients with fewer exacerbations butgreater associated morbidity) [11]. There may also be a lower threshold to prescribe long-termantibiotics in patients with a primary or secondary immunodeficiency. Common long-term oralantibiotic regimens are outlined in table 3. Where possible, antibiotic choices should be based onsputum microbiology data. While there is no evidence currently in favour of antibiotic rotationover single agent prophylaxis in terms of the development of antibiotic resistance and efficacy, it isimportant to record exacerbation rates before and after starting long-term oral antibiotics and toperform regular sputum surveillance to monitor antibiotic resistance patterns and to identify treatment emergent bacteria and fungi.

Nebulised antibiotic prophylaxis in patients with bronchiectasis

There have been a number of studies conducted using nebulised antibiotics in patients withbronchiectasis. The majority involve antipseudomonal agents, although earlier studies evaluatedthe use of nebulised amoxicillin in patients predominantly infected with H. influenzae [3, 33, 35].While the results of the nebulised amoxicillin trials are largely positive, in practice thisintervention is rarely used as high-dose oral regimens are easier and cheaper to administer.

Antipseudomonal nebulised antibiotic regimens evaluated to date include nebulised gentamicin,nebulised tobramycin, nebulised tobramycin in combination with nebulised ceftazidime and

nebulised colistin. The largest published study was performed by BARKER et al. [36] and evaluatedthe microbiological efficacy and safety of inhaled tobramycin in patients with bronchiectasisinfected with P. aeruginosa . Patients were randomly assigned to receive either tobramycin solutionfor inhalation (n537) or placebo (n537) twice daily for 4 weeks. At week 4, the tobramycinsolution for inhalation group had a mean decrease in P. aeruginosa density of 4.5 log10 colony forming units per gram (CFU?g-1) of sputum compared with no change in the placebo group(p,0.01). Logistic regression analysis showed that decreases in CFU?g-1 of sputum were significantpredictors of improved well-being. 2 weeks after cessation of the trial, P. aeruginosa was eradicatedin 35% of the tobramycin-treated group, but was detected in all placebo patients. 62% of

Table 3. Oral antibiotic prophylaxis for adult patients with bronchiectasis based on sputum microbiology


Streptococcus pneumoniae Amoxicillin 500 mg b.i.d. Clarithromycin 500 mg b.i.d.

Doxycycline 100 mg q.d.

Trimethoprim 200 mg b.i.d.Haemophilus influenzae Amoxicillin 500 mg b.i.d. Doxycycline 100 mg q.d.


Moraxella catarrhalis Amoxicillin 500 mg b.i.d. Doxycycline 100 mg q.d.

Clarithromycin 500 mg b.i.d.Staphylococcus aureus Flucloxacillin 500 mg–1 g b.i.d. Clarithromycin 500 mg b.i.d.

Doxycycline 100 mg q.d. Trimethoprim 200 mg b.i.d.

MRSA Trimethoprim 200 mg b.i.d. Doxycycline 100 mg q.d.

Stenotrophomonas maltophilia Cotrimoxazole 960 mg b.i.d. Minocycline 100 mg b.i.d.

Achromobacter xylosoxidans Minocycline 100 mg b.i.d.

q.d.: once daily; b.i.d.: twice daily; MRSA: methicillin-resistant Staphylococcus aureus .

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tobramycin-treated patients showed improvement in their medical condition compared with 38%of the placebo patients (OR 2.7, 95% CI 1.1–6.9), but there was no significant change in lungfunction between the treatment groups. Tobramycin-resistant P. aeruginosa strains developed infour (11%) out of 36 of tobramycin-treated patients and one (3%) out of 32 of placebo-treatedpatients. Three of the four patients in the tobramycin-treated group who developed resistantP. aeruginosa strains showed no microbiological response and all four failed to improve clinically.More tobramycin-treated patients than placebo patients reported increased cough, breathlessness,

wheezing and non-cardiac type chest pain, but the symptoms did not appear to limit therapy.

A second trial evaluating tobramycin solution for inhalation involved 41 bronchiectasis patientsinfected with P. aeruginosa and employed an open-label design consisting of three treatment cycles(14 days of drug therapy and 14 days off) [37]. During the 12-week treatment period significantimprovements occurred in the pulmonary symptoms severity score and in quality of lifemeasurements. However, tobramycin-resistant strains of P. aeruginosa developed in two subjectsand 10 patients dropped out due to adverse events, the most common being cough, wheeze andbreathlessness. Five subjects died during the study period due to the underlying disease, oneduring the 12-week treatment period and four during the 40-week follow-up period. None of the

deaths were considered to be related to the drug treatment.DROBNIC et al. [38] evaluated an alternative formulation of tobramycin in a double-blind placebo-controlled cross-over trial involving 30 patients. Patients received aerosolised tobramycin 300 mgor placebo twice daily for 6 months, with a 1-month wash out period between interventions. 20patients completed the protocol as three patients withdrew from the study due to bronchospasm,five patients died from respiratory failure and two others dropped out (one failed to adhere to thestudy protocol and one relocated). The number of admissions and in-patient days reduced duringthe tobramycin period. There was also a decrease in P. aeruginosa density which persisted up until3 months after nebulised tobramycin treatment had been stopped and there was no difference inthe emergence of bacterial resistance between the two study periods. However, there was no

significant difference in the number of exacerbations, antibiotic use, lung function or quality of lifebetween the tobramycin and placebo periods.

ORRIOLS et al. [39] performed a 12-month study in which patients with bronchiectasis wererandomised to receive nebulised ceftazidime 1 g b.i.d. + tobramycin 100 mg b.i.d. or symptomatictreatment. One out of eight patients in the nebulised antibiotic group withdrew having developedbronchospasm and one out of nine patients in the control group died. While there weresignificantly less admissions and in-patient days in the nebulised antibiotic group, these findingsneed to be interpreted with care owing to the open-label design of the study. Interestingly, therewas no difference in the use of oral antibiotics or change in lung function between the twotreatment groups. There was also no difference in the emergence of antibiotic resistant bacteriabetween the two treatment groups.

LIN et al. [40] performed a randomised controlled trial assessing the effect of aerosolisedgentamicin 40 mg (n516) versus 0.45% saline (n515) administered twice daily for 3 days inpatients with bronchiectasis. Gentamicin-treated patients showed significant reductions in sputumvolume and sputum inflammatory indices (there was a significant correlation between the changein sputum volume and sputum myeloperoxidase) in conjunction with significant improvements inpeak expiratory flow rate and 6-min walk distances.

MURRAY et al. [41] performed a longer term study evaluating the effect of nebulised gentamicin in

patients with bronchiectasis. 65 patients were randomised to receive gentamicin 80 mg or 0.9%saline twice daily through a nebuliser for 12 months. Inclusion criteria included a history of chronic sputum colonisation with potentially pathogenic organisms when clinically stable. After12 months, use of nebulised Gentamicin was associated with significant reductions in bacterialdensity with a 30.8% eradication rate in patients infected with P. aeruginosa and a 92.8%eradication rate in patients infected with other pathogens. There was reduced sputum purulence (8.7%versus 38.5%, p,0.001), greater exercise capacity (median (interquartile range) 510 (350–690) m

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versus 415 (267–530) m, p50.03), fewer exacerbations (median (interquartile range) 0 (0–1)versus 1.5 (1–2), p,0.001), increased time to first exacerbation (median (interquartile range) 120(87–161) days versus 61 (20–122) days, p50.02) and greater improvements in quality of life inpatients treated with gentamicin. There were no differences between groups in 24-h sputumvolume, forced expiratory volume in 1 second, forced vital capacity (FVC) or forced expiratory flow at 25–75% of FVC. There was no development of gentamicin-resistant isolates of P. aeruginosa .

Small retrospective studies have evaluated the effect of nebulised colistin in patients withbronchiectasis and P. aeruginosa infection [42, 43]. Owing to the retrospective nature of thestudies the results need to be interpreted with care, but the data suggest that nebulised colistin hasbeneficial effects in this patient population in terms of exacerbation frequency, admission rates,sputum volume and lung function. An international multicentre randomised placebo controlledtrial evaluating the effect of nebulised colistin (promixin) on time to next exacerbation in patientswith bronchiectasis and chronic P. aeruginosa infection is underway and will report in the next2 years.

Patients with bronchiectasis and P. aeruginosa chronic infection tend to have more severe lung

disease based on physiological and computed tomography parameters, a faster rate of lungfunction decline, more admissions to hospital and a worse quality of life compared with patientswith other microorganisms [44–48]. Thus, nebulised antibiotics are frequently prescribed forpatients with bronchiectasis and chronic P. aeruginosa infection in order to improve well-beingand prevent disease progression, consistent with CF management principals [14, 25]. Commonnebulised antibiotic regimens are outlined in table 4. It is important to record exacerbation ratesbefore and after starting long-term nebulised antibiotics and to perform regular sputumsurveillance to monitor antibiotic resistance patterns and treatment emergent bacteria and fungi.

Eradicating new growths of specific organisms in patients withbronchiectasis

There are no trials to date evaluating antibiotic eradication regimens in patients withbronchiectasis. However, in clinical practice, eradication regimens are often prescribed followingidentification of new growths of P. aeruginosa due to the increased morbidity associated withchronic infection [44–48]. Some of the oral and nebulised antibiotic studies in patients withbronchiectasis report variable success rates in eradicating P. aeruginosa , but these studies were notdesigned to address this specific issue and largely involved patients with chronic P. aeruginosa infection [34, 36–39, 41]. In the absence of conclusive trial data, many clinicians follow treatment

protocols used in patients with CF, where early eradication therapy and the subsequent reductionin prevalence of chronic P. aeruginosa infection is thought to have had a major impact on survival[49]. Experience suggests that eradication of P. aeruginosa is less likely once the organism hasconverted to the mucoid form, which reinforces the need for early intervention [14]. In patients

Table 4. Nebulised antibiotic prophylaxis for adult patients with bronchiectasis chronically infected withPseudomonas aeruginosa

Drug and formulation# Dose Diluent

Colistin (Colomycin) 2 MU b.i.d. 4 mL 0.9% sodium chloride

Colistin (Promixin) 1 MU b.i.d. 1 mL water for injection

Gentamicin 40 mg?mL-1 80 mg b.i.d. 1 mL 0.9% sodium chloride Tobramycin (Tobi) 300 mg b.i.d.

Tobramycin (Bramitob) 300 mg b.i.d.

Aztreonam lysine (Cayston) 75 mg t.i.d. 1 mL 0.17% sodium chlorideCeftazidime 1 g b.i.d. 3 mL water for injection

MU: million units; b.i.d.: twice daily; t.i.d.: three times daily. #: unlicensed indication.

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with CF and a new growth of P. aeruginosa , the prescription of ciprofloxacin + nebulised colistinresulted in 16% of treated patients developing chronic P. aeruginosa infection compared with 72%of untreated historical controls (p,0.005) after 3.5 years follow-up [50]. More recent data showedthat .90% of patients with CF and early P. aeruginosa infection had negative cultures 1 monthafter completing a 4-week course of nebulised tobramycin (tobi 300 mg q.i.d.) [51]. In practice,many clinicians prescribe a 3-month course of nebulised colistin in combination with oralciprofloxacin for patients with bronchiectasis and a new growth of P. aeruginosa [11, 14, 52], and

offer i.v. therapy if this intervention fails.

Eradication regimens are also commonly instituted in patients who culture MRSA in their sputumfor the first time, due to the fact that it is a resistant organism and has significant infection controlimplications. Oral rifampicin and fucidin with or without nebulised vancomycin is used in somecentres, but treatment regimens should be based around local policies.

Future antibiotic treatment strategies

It is likely that antibiotic treatment options for patients with bronchiectasis will change

significantly over the next decade. New nebulised (amikacin, aztreonam, colistin and fosfomycinin combination with tobramycin) and dry powder (ciprofloxacin, colistin and tobramycin)antibiotic formulations have been developed and may be beneficial in patients with bronchiectasis.New ways of using old antibiotics may also lead to improved outcomes. For example, due to thetime-dependent antibacterial activity of b-lactam antibiotics, continuous infusions may offersuperior efficacy compared with intermittent infusions [53], particularly in the context of severestructural lung damage and biofilm formation.

Conclusion

Antibiotics play a crucial role in the management of patients with bronchiectasis by disrupting theinfection component of the vicious circle of infection, inflammation and airway damage central tothe pathophysiology of bronchiectasis. Antibiotics can be used for treatment of exacerbations, forchronic bacterial suppression and for eradication. Antibiotic choices should be based on sputummicrobiological results. Careful monitoring is required regarding microbial resistance patterns andtreatment emergent bacteria/fungi, gastrointestinal adverse events (C. difficile infection) andantibiotic related toxicity (particularly with aminoglycosides). In the future, antibiotic options arelikely to increase through the development of new nebulised and dry powder formulations.


C.S. Haworth has received educational grants, speaker fees or performed consultancy work forChiesi, Gilead, Novartis and Forest.

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Group. 3rd Edn. Cystic Fibrosis Trust, 2009. www.cftrust.org.uk/aboutcf/publications/consensusdoc/

Antibiotic_treatment_for_Cystic_Fibrosis.pdf.

15. Smith AL, Doershuk C, Goldman D, et al. Comparison of a b-lactam alone versus b-lactam and an aminoglycoside

for pulmonary exacerbation in cystic fibrosis. J Pediatr 1999; 134: 413–421.

16. Bertenshaw C, Watson AR, Lewis S, et al. Survey of acute renal failure in patients with cystic fibrosis in the UK.

Thorax 2007; 62: 541–545.

17. Smyth A, Lewis S, Bertenshaw C, et al. Case-control study of acute renal failure in patients with cystic fibrosis in

the UK. Thorax 2008; 63: 532–535.

18. Smyth A, Tan KH, Hyman-Taylor P, et al. TOPIC Study Group. Once versus three-times daily regimen of

tobramycin for pulmonary exacerbations of cystic fibrosis – the TOPIC study: a randomised controlled trial.

Lancet 2005; 365: 573–578.

19. Foweraker JE, Laughton CR, Brown DFJ, et al. Phenotypic variability of Pseudomonas aeruginosa in sputa from

patients with acute infective exacerbation of cystic fibrosis and its impact on the validity of antimicrobial

susceptibility testing. J Antimicrob Chemother 2005; 55: 921–927.

20. Gillham MI, Sundaram S, Laughton CR, et al. Variable antibiotic susceptibility in populations of Pseudomonas

aeruginosa infecting patients with bronchiectasis. J Antimicrob Chemother 2009; 63: 728–732.

21. Smith AL, Fiel S, Mayer-Hamblett N, et al. Susceptibility testing of Pseudomonas aeruginosa isolates and clinical

response to parenteral antibiotic administration. Lack of association in cystic fibrosis. Chest 2003; 123: 1495–1502.

22. Aaron SD, Vandemheen KL, Ferris W, et al. Combination antibiotic sensitivity testing to treat exacerbations of

cystic fibrosis associated with multiresistant bacteria: a randomised, double-blind, controlled clinical trial. Lancet

2005; 366: 463–471.23. Smith DJ, Chang AB, Bell SC. Anti-inflammatory therapies in bronchiectasis. Eur Respir Mon 2011; 52: 223–238.

24. Frederiksen B, Laang S, Koch C, et al. Improved survival in the Danish center-treated cystic fibrosis patients:

results of aggressive treatment. Pediatr Pulmonol 1996; 21: 153–158.

25. Ramsey BW, Pepe MS, Quan JM, et al. Intermittent administration of inhaled tobramycin in patients with cystic

fibrosis. N Engl J Med 1999; 340: 23–30.

26. Bargon J, Dauletbaev N, Kohler B, et al. Prophylactic antibiotic therapy is associated with an increased prevalence

of Aspergillus colonization in adult cystic fibrosis patients. Respir Med 1999; 93: 835–838.

27. Harris SM, Gomell L, Shore C, et al. Chloramphenicol in the control of bronchial suppuration. Dis Chest 1952; 21:

450–454.

28. McVay LV, Sprunt DH. Antibiotic prophylaxis in chronic respiratory disease. Ann Intern Med 1953; 92: 883–886.

29. Medical Research Council. Prolonged antibiotic treatment of severe bronchiectasis; a report by a subcommittee of

the Antibiotics Clinical Trials (non-tuberculous) Committee of the Medical Research Council. BMJ 1957; 2: 255–259.30. Cherniack NS, Vosti KL, Dowling HF, et al. Long-term treatment of bronchiectasis and chronic bronchitis. Arch

Intern Med 1959; 103: 345–353.

31. Dowling HF, Mellody M, Lepper MH, et al. Bacteriologic studies of the sputum in patients with chronic bronchitis

and bronchiectasis. Results of continuous therapy with tetracycline, penicillin, or an oleandromycin-penicillin

mixture. Am Rev Respir Dis 1960; 81: 329–339.

32. Currie DC, Garbett ND, Chan KL, et al. Double-blind randomized study of prolonged higher-dose oral

amoxicillin in purulent bronchiectasis. Q J Med 1990; 76: 799–816.

33. Hill SL, Burnett D, Hewetson KA, et al. The response of patients with purulent bronchiectasis to antibiotics for

four months. Q J Med 1988; 250: 163–173.

34. Raynor CFJ, Tillotson G, Cole PJ, et al. Efficacy and safety of long-term ciprofloxacin in the management of severe

bronchiectasis. J Antimicrob Chemother 1994; 34: 149–156.

35. Stockley RA, Hill SL, Burnett D. Nebulized amoxicillin in chronic purulent bronchiectasis. Clin Ther 1985; 7:593–599.

36. Barker AF, Couch L, Fiel SB, et al. Tobramycin solution for inhalation reduces sputum Pseudomonas aeruginosa

density in bronchiectasis. Am J Respir Crit Care Med 2000; 162: 481–485.

37. Scheinberg P, Shore E. A pilot study of the safety and efficacy of tobramycin solution for inhalation in patients

with severe bronchiectasis. Chest 2005; 127: 1420–1426.

2 2 1

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H A W

O R T H



38. Drobnic ME, Sune P, Montoro JB, et al. Inhaled tobramycin in non-cystic fibrosis patients with bronchiectasis and

chronic bronchial infection with Pseudomonas aeruginosa . Ann Pharmacother 2005; 39: 39–44.

39. Orriols R, Roig J, Ferrer J, et al. Inhaled antibiotic therapy in non-cystic fibrosis patients with bronchiectasis and

chronic bronchial infection by Pseudomonas aeruginosa . Respir Med 1999; 93: 476–480.

40. Lin H-C, Cheng H-F, Wang C-F, et al. Inhaled gentamicin reduces airway neutrophil activity and mucus secretion

in bronchiectasis. Am J Respir Crit Care Med 1997; 155: 2024–2029.

41. Murray MP, Govan JR, Doherty CJ, et al. A randomised controlled trial of nebulised gentamicin in non-cystic

fibrosis bronchiectasis. Am J Respir Crit Care Med 2011; 183: 491–499.

42. Steinfort DP, Steinfort C. Effect of long-term nebulized colistin on lung function and quality of life in patients

with chronic bronchial sepsis. Int Med J 2007; 37: 495–498.

43. Dhar R, Anwar GA, Bourke SC, et al. Efficacy of nebulised colomycin in patients with non-cystic fibrosis

bronchiectasis colonised with Pseudomonas aeruginosa . Thorax 2010; 65: 553.

44. Evans SA, Turner SM, Bosch BJ, et al. Lung function in bronchiectasis: the influence of Pseudomonas aeruginosa .

Eur Respir J 1996; 9: 1601–1604.

45. Wilson CB, Jones PW, O’Leary CJ, et al. Effect of sputum bacteriology on the quality of life of patients with


46. Miszkiel KA, Wells AU, Ribens M, et al. Effects of airway infection by Pseudomonas aeruginosa : a computed

tomographic study. Thorax 1997; 52: 260–264.

47. Ho P-L, Chan K-N, Ip MSM, et al. The effect of Pseudomonas aeruginosa infection on steady-state bronchiectasis.

Chest 1998; 114: 1594–1598.

48. Martinez-Garcia MA, Soler-Cataluna JJ, Perpina-Tordera M, et al. Factors associated with lung function decline in

adult patients with stable non-cystic fibrosis bronchiectasis. Chest 2007; 132: 1565–1572.

49. Lee TW, Brownlee KG, Denton M, et al. Reduction in prevalence of chronic Pseudomonas aeruginosa infection at a

regional paediatric cystic fibrosis center. Pediatr Pulmonol 2004; 37: 104–110.

50. Frederiksen B, Koch C, Hoiby N. Antibiotic treatment of initial colonization with Pseudomonas aeruginosa

postpones chronic infection and prevents deterioration of pulmonary function in cystic fibrosis. Pediatr Pulmonol

1997; 23: 330–335.

51. Ratjen F, Munck A, Kho P, et al. Treatment of early Pseudomonas aeruginosa in patients with cystic fibrosis: the

ELITE trial. Thorax 2010; 65: 286–291.

52. Wood DM, Smyth AR. Antibiotic strategies for eradicating Pseudomonas aeruginosa in people with cystic fibrosis.


53. Hubert D, Le Roux E, Lavrut T, et al. Continuous versus intermittent infusions of ceftazidime for treating

exacerbations of cystic fibrosis. Antimicrob Agents Chemother 2009; 53: 3650–3656.

2 2 2




Chapter 15

Anti-inflammatory

therapies in

bronchiectasisD.J. Smith* ,# , A.B. Chang ",+,1 and S.C. Bell* ,#,+

Summary Although the use of anti-inflammatory therapies in bronch-iectasis remains an attractive proposition, there is currently insufficient evidence to support the use of inhaled and oralcorticosteroids, non-steroidal anti-inflammatory drugs andmacrolides. Individual patient trials may be warranted forinhaled corticosteroids and macrolides. It is hoped that recently completed and ongoing randomised control trials of macrolides

will better define the use and safety in bronchiectasis. Thereremains an urgent need to perform adequately poweredmulticentre trials of other potentially useful therapies.

It is anticipated that specialised bronchiectasis clinics willprovide greater opportunities to study disease epidemiology and pathogenesis and allow better definition of study popula-tion for inclusion within future trials. There is a need for a moredefined study population and a widely accepted definition of apulmonary exacerbation in bronchiectasis which may beapplied uniformly across studies to allow direct comparison of study outcomes. Finally, care should be taken to ensureadequate follow-up to detect potential adverse effects of new therapies, particularly on microbial resistance patterns.

Keywords: Anti-inflammatory therapy, bronchiectasis,inflammation, inhaled corticosteroids, macrolides

*Dept of Thoracic Medicine,#School of Medicine, University of Queensland, The Prince CharlesHospital, Chermside,"Queensland Children’s Respiratory Centre,+Queensland Children’s MedicalResearch Institute, Herston,Queensland, and1Menzies School of Health Research,Charles Darwin University, Darwin,Northern Territory, Australia.

Correspondence: S.C. Bell, Dept of Thoracic Medicine, The PrinceCharles Hospital, Rode Road,Chermside, Brisbane, QLD, 4032,Australia, [email protected]


B

ronchiectasis is an under-recognised condition characterised by pathological dilatation of

bronchi, persistent neutrophilic airway inflammation and, in many, chronic bacterialinfection. Bronchiectasis develops in the susceptible host through a vicious cycle of airway infection and inflammation [1]. The causes of non-cystic fibrosis (CF) bronchiectasis are diverse,the cohort populations are heterogeneous and the evidence to support therapies limited [2].Factors which may have contributed to the limited evidence for treatment are likely to includepopulation and disease severity heterogeneity, limited funding sources for clinical trials and thediverse manner that patients with bronchiectasis are managed. This appears to be changing with

2 2 3

D . J . S M I T H

E T A L .



the advent of specialised bronchiectasis clinics which are providing an opportunity to developfocused research programmes. There are a limited number of high-quality randomised controlledtrials (RCT’s) cited in recently published management guidelines for bronchiectasis [3–5].

Airway biology in bronchiectasis

Cohort studies of patients with bronchiectasis reveal Haemophilus influenzae and Pseudomonas aeruginosa to be the most frequently isolated organisms from airway secretions. Streptococcus

pneumoniae , Moraxella species and nontuberculous mycobacteria (NTM) are reported lesscommonly [6–8]. Although infection triggers inflammation, ongoing neutrophilic infiltration of the airways is apparent even in the absence of persistent infection, suggesting dysregulation of immune responses [9]. Neutrophils are the predominant inflammatory cell found in sputum andbronchoalveolar lavage fluid (BALF) in patients with bronchiectasis [9, 10]. It is hypothesised thatneutrophil apoptosis and clearance may be defective in bronchiectasis [11]. Non-apoptosed cellsdie by necrosis leading to exudation of toxic products (e.g. exoenzymes, oxygen free radicals,myeloperoxidase, etc.) which cause both localised tissue damage and provide an ongoing stimulusfor the inflammatory response. Macrophages, lymphocytes and eosinophils are similarly present in

increased number in the bronchiectatic airway, however, their role is poorly defined [12].

Acute respiratory exacerbations in patients with bronchiectasis are poorly understood but arethought to be related, in part, to increased load of existing airway bacteria and/or infection with anew bacterial pathogen. These changes provide rationale for the use of targeted antibiotics inpatients with bronchiectasis during respiratory exacerbations which are discussed in detail in thechapter by FOWERAKER and WAT [13].

Targeting inflammation in bronchiectasis

An alternative approach to targeting infection with antimicrobial agents is to attempt to modify the immune response to infection. In this chapter we focus on the use of anti-inflammatory agentsand examine the evidence for the use and potential pitfalls of these therapies. We also explorefuture treatment options and studies that are in progress.

Anti-inflammatory therapies will be discussed in one of three broad categories: 1) general anti-inflammatory therapies which have broad immunosuppressive effects on inflammatory pathways(e.g. corticosteroids or nonsteroidal anti-inflammatory drugs (NSAIDS)); 2) novel anti-inflammatory therapies which have immunomodulatory properties in addition to the cellulareffects for which they are conventionally utilised (e.g. macrolides and hydroxy-methyl-glutaryl-coenzymeA (HMGCoA) reductase inhibitors); and 3) targeted anti-inflammatory therapies whichblock a specific mediator of the immune response (e.g. anti-immunoglobulin E or anti-tumournecrosis factor (TNF)-a).

General anti-inflammatory agents

Corticosteroids

Corticosteroids have broad anti-inflammatory effects through inhibition of inflammatory mediator synthesis and release and impairment of inflammatory cell migration [14].

Corticosteroids stimulate eosinophil apoptosis but paradoxically inhibit neutrophil apoptosiswhich, in part, possibly explains their variable anti-inflammatory effectiveness in different clinicalsettings [15]. Inhaled corticosteroids improve asthma control [16, 17] and are associated withreduction in exacerbation frequency in chronic obstructive pulmonary disease (COPD) [18], yettheir withdrawal in patients with CF has minimal impact on symptoms, lung function orexacerbations [19]. Short courses of oral steroids have an established role in the treatment of exacerbations of asthma and COPD [20, 21]; however, their role in CF is more controversial [22].

2 2 4

A N T I - I N F L A M M A T O R Y

T H E R A P Y



Inhaled corticosteroids

Recently, KAPUR et al. [23] identified six RCTs of inhaled steroids in non-CF bronchiectasis(table 1). The meta-analysis of these studies failed to provide conclusive evidence that inhaledcorticosteroids result in a clinically significant improvement in lung function, affect exacerbationrates or improve quality of life in patients with bronchiectasis (fig. 1).

The earliest study, published in 1992 by ELBORN et al. [24], enrolled 20 patients in a 12-week crossover trial of high-dose beclomethasone diproprionate/placebo (6 weeks drug, 6 weeksplacebo). Despite five patients dropping out of the study, the authors reported an 18% reductionin volume of sputum and reduced bronchoprovocation during histamine challenge testing. Asubsequent study demonstrated inhaled fluticasone diproprionate reduced sputum levels of pro-inflammatory mediators (interleukin (IL)-8, leukotriene B4 (LTB4) and IL-1b) and sputumleukocyte density in bronchiectasis [25]. Combined with the consistent finding that inhaled steroidshave no effect on sputum bacterial load [25], this suggests that any beneficial effect they may exert ismost likely explained by anti-inflammatory as opposed to antimicrobial activity. Studies by TSANG

et al. [26] and JOSHI andSUNDARAM [27] reported no change in exhaled nitric oxide and no change in

lung function, respectively.Two larger and longer trials studying fluticasone diproprionate (500 mg b.i.d.) in adults withbronchiectasis, demonstrated a reduction in sputum quantity [28, 29]. In a post hoc analysis TSANG

et al. [28] observed that this effect was most pronounced in those patients with chronic P. aeruginosa infection. However, each of these studies had significant limitations including no placebo arm in theformer and variable baseline sputum production in the treatment arms in the latter, precluding theirdata from being included in the assessment of this outcome measure in the Cochrane Review.Although therapy was generally well tolerated for the duration of the trials, long-term safety isuncertain in dosage regimens which would currently be considered to be high. In addition, one short-term study [25], the data on density of total bacteria, commensal bacteria and P. aeruginosa in sputum

showed an increasing trend after 4 weeks of therapy with inhaled steroids.

Based on the available evidence from these published studies, KAPUR et al. [23] concluded that there iscurrently insufficient evidence of both benefit and safety to recommend routine use of inhaledcorticosteroids in patients with bronchiectasis, however, it may be appropriate to consider a trial inseverely symptomatic patients on a case by case basis, with close monitoring for adverse effects.

Oral corticosteroids

There is currently no evidence supporting the use of oral corticosteroids. A Cochrane Review by

LASSERSON et al. [30] failed to identify any RCTs in non-CF bronchiectasis either for short-term(during an exacerbation) or long-term use. The only evidence of potential benefit is from thepaediatric CF literature in which prednisolone at a dose of 1 mg?kg-1 on alternate days wasassociated with reduced rate of lung function decline [22]. The long-term adverse effects includingeffects on growth and cataract resulted in the early termination of the trial.

NSAIDS

NSAIDS non-selectively block the activation of the cyclo-oxygenase pathway of pro-inflammatory prostaglandins. A landmark placebo controlled RCT examined the effects of ibuprofen in people

with CF [31]. The study included 85 patients (age range 5–39 years) and demonstrated that thosetreated with high-dose ibuprofen (dose range 16.2–31.6 mg?kg-1) experienced a slower rate of decline in forced expiratory volume in 1 second (FEV1), as well as improved maintenance of weight when compared with control subjects over the 4-year study period. Post hoc analysisrevealed these effects to be most pronounced in those participants ,13 years of age at study commencement. Ibuprofen therapy was well tolerated with only one patient withdrawing due toside-effects clearly attributable to ibuprofen (conjunctivitis and epistaxis).

2 2 5

D . J . S M I T H

E T A L .



T a b l e 1 . R a n d o m

i s e d c o n t r o l l e d t r i a l s o f i n h a l e d c o r t i c o s t e r o i d s i n b r o n c h i e c t a s i s

S t u d y

C o u n t r y

D e s i g n

P o p u l a t i o n

I n

c l u s i o n

c r i t e r i a

D r u g

P l a c e b o

D u r a t i o n

S u b j e c t s

n

O u t c o m e

m e a s u r e s

F i n d i n g s

A d v e r s e

e v e n t s

E L B O R N

[ 2 4 ]

U K

D B R C T

( c r o s s o v e r )

A d u l t s ( 3 0 –

6 5 y r s )

B r o n c h i e c t a s i s ,

n o p r i o r

o r a l / i n h a l e d

c o r t

i c o s t e r o i d s

B e c l o m e t h a s o n e

d i p r o p r i o n a t e

( 7 5 0 m g b . i . d . )

Y e s

1 2 w e e k s

( 6 w e e k s

e a c h a r m ,

n o w a s h o u t )

2 0

L

u n g f u n c t i o n ,

P D 2 0 m e t a c h o l i n e ,

s p

u t u m

p r o d u c -

t i o

n , p u l m o n a r y

s y m p t o m s

I m p r o v e d F E V

1 ,

i m p r o v e d m o r n

i n g

P E F R , i m p r o v

e d

c o u g h , r e d u c e d

s p u t u m

v o l u m

e

O r a l

c a n d i d i a s i s

( n 5 1 )

T S A N G

[ 2 5 ]

C h i n a

( H o n g

K o n g )

D B R C T

( p a r a l l e l )

A d u l t s

( m e a n a g e

5 5 y r s )

B r o n c h i e c t a s i s

. 1 0

m L s p u t u m

p

e r 2 4 h

F l u t i c a s o n e

p r o p r i o n a t e

( 5 0 0 m g b . i . d . )

Y e s

4 w e e k s

2 4

2 4 h s p u t u m

( v o l u m e / l e u k o c y t e

c o

u n t s / m i c r o b i a l

c o

n c e n t r a t i o n s /

I L - 1 / I L - 8 / T N F - a /

L T B 4 ) ,

l u n g f u n c t i o n

R e d u c e d s p u t u m

l e u k o c y t e d e n s

i t y ,

r e d u c e d I L - 1 b ,

I L - 8 a n d L T B 4 ,

n o c h a n g e i n s p

u t u m

v o l u m e , n o c h a n

g e i n


N o n e r e p o r t e d

b u t t r e n d

t o w a r d s

i n c r e a s e d

s p u t u m

d e n s i t y

o f c o m m e n s a l

f l o r a a n d

P . a e r u g i n o s a

T S A N G

[ 2 6 ]

C h i n a

( H o n g

K o n g )

R C T

( p a r a l l e l )

A d u l t s

( m e a n a g e

5 6 y r s )


n o n s m o k e r s



( 5 0 0 m g b . i . d . )

Y e s

5 2 w e e k s

6 0

e N O

N o c h a n g e i n e

N O

N o t r e p o r t e d

J O S H I

[ 2 7 ]

I n d i a

D B R C T


A d u l t s /

c h i l d r e n

( 1 5 – 6 0 y r s )


1 2 %

i m p r o v e m e n t

p o s t -

b r o n c h o d i l a t o r

F E V 1

B e c l o m e t h a s o n e

d i p r o p r i o n a t e

( 4 0 0 m g b . i . d . )

Y e s

8 w e e k s

( 4 w e e k s

e a c h a r m ,

2 w e e k

w a s h o u t )

2 0

L

u n g f u n c t i o n

N o c h a n g e i n


N o n e

T S A N G

[ 2 8 ]

C h i n a

( H o n g

K o n g )

D B R C T

( p a r a l l e l )

A d u l t s

( m e a n a g e

5 8 y r s )

B r o n c

h i e c t a s i s , n o

o r a l / i n h a l e d

c o r t

i c o s t e r o i d s



( 5 0 0 m g b . i . d . )

Y e s

5 2 w e e k s

8 6

S p u t u m

v o l u m e

a n d p u r u l e n c e ,

e x a c e r b a t i o n r a t e s ,



v o l u m e , n o c h a n

g e i n

e x a c e r b a t i o n r a

t e s ,

s p u t u m

p u r u l e n c e ,


S o r e t h r o a t

( n 5 7 )

M A R T I N E Z -

G A R C I A

[ 2 9 ]

S p a i n

R C T - n o n

D B #

( p a r a l l e l )

A d u l t s

( m e a n a g e

6 9 y r s )

B r o n c h i e c t a s i s



( 5 0 0 m g b . i . d . o r

2 5 0 m g b . i . d . )

Y e s

3 6 w e e k s

9 3

H R Q o L

I m p r o v e d d y s p n

o e a ,

r e d u c e d s p u t u m

v o l u m e , r e d u c

e d

b - a g o n i s t u s

e

( h i g h - d o s e g r o

u p )

D r y m o u t h ( n 5 8 ) ,

l o c a l i r r i t a t i o n

( n 5 4 ) , d y s p h o n i a

( n 5 4 ) , o r a l

c a n d i d i a s i s

( n 5 2 ) , a p h t h o u s

u l c e r ( n 5 1 )

D B R C T : d o u b l e - b l i n d ( D B ) r a n d o m i s e d c o n t r o l l e d t r

i a l ( R C T ) ; b . i . d . : t w i c e d a i l y ; F E V 1 :

f o r c e d e x p i r a t o r y v o l u m e i n 1 s e c

o n d ; P D 2 0 : p r o v o c a t i v e d o s e c a u

s i n g a 2 0 % f a l l i n F E V 1 ;

P E F R : p e a k e x p i r a t o r y f l o w r a t e ; I L : i n t e r l e u k i n ; T N

F - a : t u m o u r n e c r o s i s f a c t o r - a ; L T

B 4 : l e u k o t r i e n e B 4 ; P . a e r u g i n o s a : P s e u d o m o n a s a e r u g i n o s a ; e N O : e x h a l e d n i t r i c o x i d e ;

H R Q o L : h e a l t h - r e l a t e d q u a l i t y o f l i f e .

# : t h e o n l y b l i n d e d c o m p o n e n t o f t h i s s t u d y w a

s f o r t h e d o s e o f i n h a l e d c o r t i c o s t e r o i d s .

2 2 6


T H E R A P Y



A Cochrane Review by LANDS and STANOJEVIC [32] of NSAIDs in CF, including four RCTs,concluded that high-dose ibuprofen is capable of slowing disease progression; whilst NSAIDs arean attractive potential therapy in patients with bronchiectasis the benefits of treatment

Study or subgroup

Heterogeneity:χ2

= 0.59, df = 2 (p = 0.74); I2

= 0%Test for overall effect: Z = 3.04 (p = 0.002)

FEV1 L#

Subtotal (95% Cl)

Heterogeneity:χ2 = 0.05, df = 2 (p = 0.98); I2 = 0%Test for overall effect: Z = 2.66 (p = 0.008)

FVC L#

Subtotal (95% Cl)

Heterogeneity:χ2

= 0.01, df = 1 (p = 0.93); I

2

= 0%Test for overall effect: Z = 1.03 (p = 0.30)

Diffusion capacity % pred¶

Subtotal (95% Cl)


RV % pred¶

Subtotal (95% Cl)


TLC % pred¶

Subtotal (95% Cl)


Peak flow L.min

-1#

ICS

Mean±SD

Placebo

Mean±SD

Total

10

291251

10

281250

27.7

71.50.8100

0.06 (-0.05_0.17)

0.20 (-0.45_0.85)0.10 (0.03_0.17)

0.09 (0.03_0.15)

0.11 (-0.04_0.25)

0.10 (-0.70_0.90)

0.09 (0.01_0.16)

24.80 (-9.35_58.95)

26.23 (-5.84_58.31)37.00 (-56.56_130.56)

2.70 (-2.49_7.89)

2.65 (-2.39_7.68)1.80 (-18.58_22.18)

2.00 (-16.46_20.46)

-2.43 (-19.41_14.55)-26.80 (-70.08_16.48)

3.20 (-1.99

_

8.39)

2.55 (-2.39_7.49)

250-25

Favours placebo Favours ICS

-50 50

-3.70 (-19.77_12.37)

0.09 (0.02_0.16)

23.0

76.3

0.7

88.211.8100

93.9

6.1100

84.6

15.4100

90.59.5100

100

10

28

1250

10

29

12

101222

101222

29

1241

28

1240

29

1241

10

1222

291241

281240

51

0.011±0.11

0.2±0.870.064±0.154

-0.045±0.14

0±0.7390.038±0.107

-0.067±0.16

0±1

-0.062±0.181

-7.8±47.82-2±122.58

84.2±10

70±21.86

106±29.2

135.8±59.46

86.4±1087.5±20.83

0.038±0.16

0.1±1

0.025±0.104

17±27.3635±111

86.9±10

71.8±28.63

108±10

109±48.11

89.6±1083.8±19.32

Total Weight

%Mean difference

IV, fixed, 95% Cl

Mean difference

IV, fixed, 95% Cl

◆

◆

◆

◆

JOSHI [27]

MARTINEZ [29]TSANG [25]Subtotal (95% Cl)

JOSHI [27]

MARTINEZ [29]

TSANG [25]

JOSHI [27]TSANG [25]

MARTINEZ [29]TSANG [25]

MARTINEZ [29]

TSANG [25]

MARTINEZ

[29]TSANG [25]

Figure 1. Forest plot of lung function indices comparing adults with bronchiectasis (in stable state) on inhaled

corticosteroids (ICS) versus controls. FEV1: forced expiratory volume in 1 second; FVC: forced vital capacity; %

pred: % predicted; RV: residual volume; TLC: total lung capacity. #: end study minus baseline values; ": end of study values. Reproduced from [23] with permission from the publisher.

2 2 7

D . J . S M I T H

E T A L .



demonstrated in patients with CF cannot necessarily be extrapolated. This has been demonstratedwith the use of human recombinant DNase, which when trialled in non-CF bronchiectasis resultedin increased pulmonary exacerbations and greater decline in lung function [33].

Two recent Cochrane Reviews of oral and inhaled NSAID therapy in non-CF bronchiectasis wereable to identify only one study suitable for inclusion [34, 35]. In this study 25 adults with chroniclung disease (eight bronchiectasis, 12 chronic bronchitis and five diffuse panbronchiolitis) received

inhaled indomethacin or placebo for 14 days. In the treatment group (inhaled indomethacin)compared with placebo, there was a significant reduction in sputum production over 14 days(difference -75 g?day -1; 95% CI -134.61– -15.39) and significant improvement in dyspnoea score(difference -1.90; 95% CI -3.15– -0.65). There was no significant difference between groups inlung function or blood indices [36].

Novel immunomodulatory agents

Macrolides

Macrolides have been in clinical use as antimicrobial agents for .50 years. There are three classesof macrolides based on the central ring structure: 14-membered ring macrolides (e.g.erythromycin, roxithromycin and clarithromycin); 15-membered ring macrolides (also knownas ‘‘azolides’’, e.g. azithromycin); and 16-membered ring macrolides (e.g. spiramycin and

josamycin) (fig. 2). The variation in structure of each class influence pharmacokinetic andpharmacodynamic properties [38]. Importantly, compared with other classes, the 15-memberedring structure azolides have less drug interaction, improved gastrointestinal tolerance andenhanced ability to concentrate within the neutrophil [39].

Antimicrobial properties

Macrolides exert their antimicrobial action against Gram-positive, Gram-negative and intracellularorganisms by binding to ribosomal subunits required for protein replication. Of particular relevanceto their use in bronchiectasis is their antimicrobial activity against H. influenzae , Moraxella catarrhalis and S. pneumoniae . Similarly their activity against ‘‘atypical’’ respiratory pathogens(including Legionella pneumophila, Chlamydia spp. and Mycoplasma pneumoniae ) has led to theirwidespread usage in the treatment of community-acquired pneumonia [40, 41].

At least two compounds (clarithromycin and azithromycin) have demonstrated activity in NTMinfection and are important components of multi-drug regimes for treatment of Mycobacteriumavium complex [42]. If adherence to treatment regimens is poor or if macrolide monotherapy isadministered, NTM species may develop resistance. This may result in poorer clinical outcome [43].This is a major concern when macrolides are prescribed in disease processes where mycobacterialinfections can co-exist. The recently published Australia and New Zealand bronchiectasis guidelinesrecommend screening for NTM prior to initiation of macrolide therapy and regular sputumsurveillance during treatment [5].

Anti-pseudomonal properties

The reported prevalence of P. aeruginosa infection in bronchiectasis varies from 12% to 33% [8]and is associated with radiological disease severity [44], increased lung function decline [45] andmortality [46]. Mucoid transformation of P. aeruginosa allows alginate secretion and biofilmproduction which provides a physical barrier from the immune system and contributes topersistent airway infection and inflammation [47]. P. aeruginosa within biofilms can communicatethrough quorum sensing systems (las and rhl) which are important in coordination of theexpression of virulence factors and biofilm maturation [48]. Azithromycin has been shown tosuppress both lasI and rhlI in vitro [49].

2 2 8


T H E R A P Y



P. aeruginosa is considered to be inherently resistant to macrolides as the in vitro minimalinhibitory concentration (MIC) is significantly higher than the concentration achievable in vivo [50]. However sub-MIC concentrations of macro-lides may inhibit P. aeruginosa virulence. Type IVpili on the surface membrane of P. aeruginosa

increase the organism’s motility and are believedto be critical in adhesion of P. aeruginosa toepithelial cells and colony expansion, and infacilitating biofilm formation. Sub-MIC concen-trations of clarithromycin inhibit adherence of P.aeruginosa to cell surface pili and retard biofilmmaturation in vitro [50].

Macrolides have also been shown to suppressvarious P. aeruginosa virulence factors includingprotease, elastase, leucocidin, pyocyanin, phos-pholipase C and exotoxin A [51–53]. Suppressionof P. aeruginosa virulence varied depending on P.aeruginosa strains studied and the specific macro-lide used. In general, azithromycin has beenshown to be more effective than other macrolides[51, 52]. Azithromycin has also been shown toinhibit P. aeruginosa antibiotic efflux pumpsthereby potentially contributing to synergy andincreasing the efficacy of other classes of anti-microbials [54]. Although these studies suggest

macrolides are capable of impairing P. aeruginosa virulence, it is important to highlight that most of these studies were performed with laboratory strains of P. aeruginosa using in vitro systems.

Anti-inflammatory properties

Anti-inflammatory properties of macrolides werefirst considered in the 1970s when observationalstudies noted that steroid-dependent asthmatics

were able to reduce their dose of oral corticoster-oid dose while prescribed erythromycin andtriacetyloleandomycin [55]. The steroid sparingeffect was later confirmed in prospective studies inpatients with severe corticosteroid dependentasthma [56]. Furthermore, a reduction in bron-chial hyperreactivity in asthmatic subjects wasseen in patients receiving erythromycin, clarithro-mycin or roxithromycin [57–59].

However, it was in the 1980s when use of macrolides revolutionised the treatment of diffusepanbronchiolitis (DPB) that their immunomodulatory properties came under closer scrutiny.DPB is an idiopathic inflammatory airway condition found almost exclusively within the SouthEast Asian populations (especially in Japan), which histologically is characterised by intenseneutrophilic inflammation of the bronchioles [60]. Its typical onset is in the second to fifth decadeof life which, when untreated, progresses to severe bronchiectasis, chronic airway infection and

CH3

CH3

CH3

CH3

CH3

O

O

O

OO

OOH

OH

OO

H3C

HO

HO

HON

H3C

H3C

CH3

CH3

CH3

CH3

CH3

CH3

OO

OO

O

O

O

CH3

CH3

CH3

CH3

CH3

CH3

CH3

CH3

CH3

CH3

HO

HO

HO

OH

OH

N

N

H3C

H3C

H3C

H3C

CH3

CH3CH3

CH3

CH3 CH3

CH3

CH3

CH3CH3

OO

O

O

OO

O

O O

OH

OH

OH

OH

OH

N

N

H3C

a)

b)

c)

Figure 2. Structure of macrolides (representative

examples). a) 14-membered ring (erythromycin);

b) 15-membered ring (azithromycin); and c) 16-

membered ring (spiramycin I). Reproduced from[37] with permission from the publisher.

2 2 9

D . J . S M I T H

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ultimately respiratory failure. Prior to the introduction of macrolides in the mid 1980s, 10-yearsurvival rates were low (,33%) [61], and even lower in those patients with chronic P. aeruginosa infection [62]. Since the introduction of erythromycin and subsequently other macrolides, survivalhas improved dramatically achieving 10-year survival rates .90% [61].

Immunomodulatory properties

Herin we briefly review the supportive evidence with more comprehensive reviews in the literature[63, 64]. While anti-inflammatory actions of macrolides are well established, the differences seenin some studies are probably attributable to variance in methodology, model system used and themacrolide agent studied.

Endotoxins produced by invading bacteria stimulate human epithelial cells both directly andthrough toll-like receptors, triggering an inflammatory cascade leading to the activation of nuclearfactor (NF)-kb [65]. NF-kb is central in regulating transcription of genes which encode pro-inflammatory mediators, including IL-6, IL-8, TNF-a (cytokines) and the intercellular adhesionmolecule-1 (ICAM-1). In vitro studies have demonstrated both erythromycin and clarithromycin

to be capable of inhibiting NF-kb activation [66, 67] and complimentary studies haveindependently demonstrated release of lower levels of IL-1, IL-6, IL-8 and ICAM-1 fromactivated bronchial epithelial cells when exposed to macrolides [68–70].

Neutrophils recruited to the site of inflammation become activated allowing phagocytosisof microorganisms and production of proteases (including neutrophil elastase and matrix-metalloproteinases (MMP)-9), and reactive oxygen species (ROS) responsible for the ‘‘oxidativeburst’’ believed to be fundamental to killing the phagacytosed microorganism [71, 72]. In thesetting of infection, spillage of these proteases and ROS from necrotic neutrophils contributestowards localised tissue damage and provides ongoing stimulus to the inflammatory process.Macrolides are able to modulate neutrophil function by several mechanisms. In an animal model

of bronchiectasis, macrolides inhibit ICAM-1 expression which may reduce neutrophil migrationto the site of inflammation [64]. Various 14-membered macrolides have been shown to inhibit theoxidative burst [72] and similarly erythromycin and flurythromycin inhibit the release of neutrophil elastase [73].

Interestingly, macrolides are associated with increased neutrophil degranulation [63]. A short-term study of the effect of azithromycin (3 days) in healthy volunteers demonstrated animmediate increase in neutrophil degranulation and circulating ROS, but decreased IL-8. This wasfollowed by a delayed inhibitory effect on oxidative burst, myeloperoxidase, IL-6 and increasedneutrophil apoptosis [74]. These in vitro studies provide impetus for studying the potential impact

of macrolides on neutrophil dominated airway diseases such as bronchiectasis.

Macrolides and mucus hypersecretion

Mucus hypersecretion is a hallmark of bronchiectasis, which in combination with impairedmucociliary clearance produces a local environment conducive to chronic infection. Mucins(macromolecular glycoproteins) are major constituents of mucus and are encoded by a number of genes. One such gene, MUC5AC is specifically expressed by bronchial epithelial goblet cells [75] andin vitro studies demonstrate erythromycin and clarithromycin attenuate lipopolysaccharide-inducedincreased MUC5AC gene expression [64]. Azithromycin demonstrates similar effects on the

MUC5AC gene in P. aeruginosa quorum sensing mediator stimulated human epithelial cells [76].These effects are supported by in vivo responses to macrolides in varied animal models [77, 78].

In summary, the potential benefits of macrolide therapy in patients with bronchiectasis may resultfrom antimicrobial properties and effects on biofilm development in patients with P. aeruginosa infection, by down-regulating acute and chronic inflammatory responses and limiting mucushypersecretion.

2 3 0


T H E R A P Y



Clinical trials of macrolides

To date there have been limited studies examining the effectiveness of macrolides for treatment of non-CF bronchiectasis. Those published studies have been performed in small patient populationsand have varied considerably in study design including duration, dose and specific macrolide,outcome measures and whether a control group was used as a comparator (table 2).

The first double-blind, placebo-controlled RCT of macrolides in non-CF bronchiectasis comparedthe effect of roxithromycin (4 mg?kg-1 b.i.d.)/placebo for 12 weeks in children with a clinicaldiagnosis of bronchiectasis and evidence of airway hyperreactivity [79]. There was a significantreduction in sputum purulence, leukocyte concentration and a reduction in airway reactivity (provocative dose causing a 20% fall in FEV1 to metacholine). However, there was no change inlung function when compared with placebo.

In a second macrolide trial also in children with stable non-CF bronchiectasis, YALCIN et al. [80]compared the impact of clarithromycin with conventional treatment administered for 3 monthson immune mediators within BALF. The study demonstrated greater reduction in sputum volumeand BALF total cell counts, neutrophil ratios and IL-8 levels in the clarithromycin group.

Interestingly, there was no significant change in sputum microbiology. This study had the majorlimitation of the lack of a placebo.

A double-blind RCT of erythromycin in adults with non-CF bronchiectasis compared 8 weeksof erythromycin (500 mg b.i.d., n514) with placebo (10 patients) during a period of clinicalstability [81]. Three patients, each receiving erythromycin withdrew (adverse effect n51, pooradherence n52). A ‘‘per protocol’’ analysis based on those who completed the trial demon-strated an improvement in lung function (mean increase in FEV1 and forced vital capacity of 140 mL and 120 mL, respectively) and decreased sputum production in those receivingerythromycin. There were no differences in levels of inflammatory cytokines (IL-8, TNF-a or

LTB4) in sputum.Several uncontrolled studies have also been reported. An open label, randomised, crossover study of 6 months of azithromycin 500 mg twice weekly and standard treatment in 12 patients (11included in analysis) demonstrated a reduction in the number of exacerbations requiringantibiotics (five versus 16, p,0.019) and sputum volume during azithromycin therapy and nochange in lung function [82]. Notably, the investigators aimed to recruit 30 subjects for the study based on pre-study power estimates.

A prospective cohort study of azithromycin in adult patients with frequent pulmonary exacerbations (.4 in the year prior to enrolment), employed a treatment protocol of azithromycin

500 mg?

day

-1

for 6 days, then 250 mg?

day

-1

for 6 days, followed by maintenance treatment of 250 mg three times per week [83]. Six (15%) of the 39 patients recruited withdrew due to adverseeffects. Analysis based on those who tolerated therapy demonstrated a reduction in exacerbationrate (from 0.71 to 0.13 per month, p,0.001), reduction in number of courses of antibiotics (0.08to 0.003 per month, p,0.001) and a trend to improvement in lung function parameters.Respiratory symptoms improved in those treated with azithromycin over a mean follow-up periodof 20 months (in-house symptom questionnaire).

Finally a cohort study of 56 adult patients treated with azithromycin 250 mg three times per week,of which 50 patients completed a minimum of 3 months (mean duration 9.1 months),demonstrated a reduction in exacerbation rate and sputum production (compared with the

6 months prior to treatment) and an improvement in FEV1 (only 29 patients assessable) [84].

In summary, these small studies have demonstrated that macrolide therapy is generally welltolerated and reduces sputum volume, however, effect on pulmonary function is unclear. Severalstudies have reported significant participant dropout due to gastrointestinal adverse events.Routine use of macrolides cannot be supported based on current evidence and there is an urgentneed for large randomised placebo controlled trials to assess tolerability, clinical impact, which

2 3 1

D . J . S M I T H

E T A L .



T a b l e 2 . C l i n i c a l

t r i a l s o f m a c r o l i d e t h e r a p y i n b r o

n c h i e c t a s i s

S t u d y

C o u n t r y

D e s i g n

P o p u l a t i o n

I n c l u

s i o n

c r i t

e r i a

D r u g

P l a c e b o

D u r a t i o n

S u b j e c t s

n

O u t c o m e

m e a s u r e s

F i n d i n g s

A d v e r s e

e v e n t s

K O H [ 7 9 ]

S o u t h

K o r e a

D B R C T

( p a r a l l e l )

C h i l d r e n

( m e a n a g e

1 3 y r s )


a i r w a y

h y p e r r e

a c t i v i t y

R o x i t h r o m y c i n

( 4 m g ? k g - 1

b . i . d . )

Y e s

1 2 w e e k s

2 5

S p

u t u m

p u r u l e n c e / W C C ,

F E V 1 , P D 2 0

m e t a

c h o l i n e


p u r u l e n c e / l e u k o c y t e

c o u n t s , r e d u c e d a i r w

a y

r e a c t i v i t y , f a l l i n F E V 1

N o n e

Y A L C I N

[ 8 0 ]

T u r k e y

R C T

( p a r a l l e l )

C h i l d r e n

( 7 – 1 8 y r s )


n o a n t i b

i o t i c s i n

p r i o r 1 6

w e e k s

C l a r i t h r o m y c i n

( 1 5 m g ? k g - 1

b . i . d . )

N o

1 2 w e e k s

3 4

S p u t u m

v o l u m e ,

l u n g f u n c t i o n ,

B A L F ( l e u k o c y t e

c o u n t s , m i c r o b i a l

c u l t u r e s , I L - 8 ,

I L - 1 0

, T N F - a )


v o l u m e , r e d u c e d B A

L F

n e u t r o p h i l r a t i o , I L -

8 ,

i n c r e a s e d F E F 2 5 – 7 5 ,

N o

c h a n g e i n F E V 1

N o n e

T S A N G

[ 8 1 ]

C h i n a

( H o n g

K o n g )

D B R C T

( p a r a l l e l )

A d u l t ( m e a n

a g e 5 5 y r s )

B r o n c h

i e c t a s i s

. 1 0

m L

s p u t u

m

p e r

2 4

h

E r y t h r o m y c i n

( 5 0 0 m g b . i . d . )

Y e s

8 w e e k s

2 4

2 4 h

s p u t u m

( v o l u m

e / W C C /

m i c r o b i a l

c o n c e n t r a t i o n s /

i m m u n e m e d i a t o r s

# ) ,

l u n g

f u n c t i o n


v o l u m e , i m p r o v e d F E V 1

a n d F V C , n o c h a n g e i n

m i c r o b i a l c o n c e n t r a t i o n ,

n o c h a n g e i n i m m u n e

m e d i a t o r s

W i t h d r e w d u e t o

r a s h ( n 5 1 )

C Y M B A L A

[ 8 2 ]

U S A

O p e n l a b e l


A d u l t

( m e a n a g e

7 1 y r s )

B r o n c h

i e c t a s i s

A z i t h r o m y c i n

( 5 0 0 m g b . i . d . )

N o

5 2 w e e k s

( 2 6 w e e k s

e a c h a r m ,

4 w e e k s

w a s h o u t )

1 2

S p u t u m

v o l u m e ,


r a t e s , l u n g f u n c t i o n


v o l u m e , r e d u c e d

e x a c e r b a t i o n s , n o

c h a n g e i n l u n g f u n c t i o n

D i a r r h o e a ( n 5 3 )

D A V I E S

[ 8 3 ]

U K

C o h o r t

A d u l t

( 1 8 – 7 7 y r s )


.

4

e x a c e r b a t i o n s

p r i o r 5 2

w e e k s


( 5 0 0 m g q . d .

6 d a y s ,

2 5 0 m g q . d .

6 d a y s ,

2 5 0 m g M W F )

N o

M e a n

8 0 w e e k s

3 9

E x a c e r b a t i o n

r a t e s ,

a n t i b i o t i c

u s a g e , l u

n g f u n c t i o n

R e d u c e d e x a c e r b a t i o n

r a t e , r e d u c e d a n t i b i o t i c

u s a g e , i m p r o v e d

D L , C O , n o c h a n g e

i n F E V 1 , F V C

W i t h d r e w ( n 5 6 ) ;

a b n o r m a l l i v e r

f u n c t i o n ( n 5 2 ) ,

d i a r r h o e a ( n 5 2 ) ,

r a s h ( n 5 1 ) ,

t i n n i t u s ( n 5 1 )

A N W A R

[ 8 4 ]

U K

C o h o r t

A d u l t

( m e a n a g e

6 3 y r s )


o

3

e x a c e r b a t i o n s

p r i o r 2 6

w e e k s


( 2 5 0 m g M W F )

N o

2 0 4 w e e k s

5 6

E x a c e r b

a t i o n r a t e s ,

l u n g f u n c t i o n ,

s p u t u m

v o l u m e /

m i c r o b i o l o g y


v o l u m e , r e d u c e d

e x a c e r b a t i o n r a t e s

,

r e d u c e d p o s i t i v e s p u

t u m

m i c r o b i a l c u l t u r e s

W i t h d r e w

( n 5 6 ) " ; d i a r r h o e a

( n 5 3 ) , a b d o m i n a l

c r a m p s ( n 5 2 ) ,

s k i n r a s h ( n 5 2 )

D B R C T : d o u b l e - b l i n d r a n d o m i s e d c o n t r o l l e d t r i a l ( R C T ) ; b . i .

d . : t w i c e d a i l y ; W C C : w h i t e c e l l c o u n t ; F E V 1 : f o r c e d e x p i r a t o r y v o l u m

e i n 1 s e c o n d ; P D 2 0 : p r o v o c a t i v e d

o s e c a u s i n g a 2 0 % f a l l i n

F E V 1 ; B A L F : b r o n c h o a l v e o l a r l a v a g e f l u i d ; I L : i n t e r l e u k i n

; T N F : t u m o u r n e c r o s i s f a c t o r ; F V C : f o r c e d v i t a l c a p a c i t y ; F E F 2 5 – 7 5 % : f o r c e d e x p i r a t o r y f l o w a t 2 5 – 7 5 % F V C

; q . d . : o n c e d a i l y ; D L , C O :

d i f f u s i n g c a p a c i t y o

f t h e l u n g f o r c a r b o n m o n o x i d e ; M W F : M o n d a y , W e d n e s d a y , F r i d a y .

# : i m m u n e m e d i a t o r s : I L - 1 a , T N F - a

a n d l e u k o t r i e n e B 4 ;

" : s e v e n a d v e r s e e v e n t s i n s i x p a t i e n t s .

2 3 2


T H E R A P Y



macrolide is most beneficial and to assess the risk of macrolide resistant infections. This latterpoint is important given the emerging evidence of macrolide resistance in Europe [85–87] and in theCF population [88–90]. Several studies have either recently been completed, are actively recruiting orabout to commence, which will hopefully address some of these important issues (table 3).

HMGcoA reductase inhibitors

HMGcoA reductase inhibitors (‘‘statins’’) have established clinical utility as lipid lowering agentsin patients with hyperlipidaemia. They also have widely recognised anti-inflammatory andimmunomodulatory properties. In vitro studies of HMGCoA reductase inhibitors havedemonstrated inhibition of neutrophil migration and epithelial cell production of chemoat-tractants and proteases and potentiation of macrophage efferocytosis [72].

In animal models of COPD, simvastatin has been shown to inhibit airway remodelling, lowerTNF-a and MMP-9 levels and reduce peribronchial and perivascular inflammation [91, 92]. Arecent systematic review identified nine studies using HMGCoA reductase inhibitors in patientswith COPD [93], however, only one of these was a prospective RCT. Collectively, these studiesdemonstrated beneficial effects on pulmonary function, exacerbation rates and mortality andprovide the foundation for further study. Large, prospective RCTs are currently underway. Studiesin asthmatic subjects have yielded more variable results. Reduction in airway hyperreactivity hasbeen seen in one study [94], no benefit in another [95] and one retrospective review evensuggested HMGCoA reductase inhibitor use was associated with poorer clinical outcomes [96]. Arecent placebo-controlled, double-blind RCT of simvastatin 40 mg?day -1 in patients with steroidresponsive (eosinophilic) asthma failed to demonstrate any clinically significant steroid sparingeffect from the addition of simvastatin [97].

There are currently no studies of the use of HMGCoA reductase inhibitors for bronchiectasis, however,the findings of the studies in other airway diseases suggest that future studies are worthwhile.

Targeted agents

There are currently no phase III trials of targeted therapies in inflammatory airway diseases, however, anumber of potential candidate agents specifically targeting neutrophilic inflammation are underinvestigation.

The CXC chemokines and their associated receptors (CXCR1/CXCR2) are believed to have a key role in neutrophilic inflammation in pulmonary disease and recently a number of agents whichinhibit this pathway have been developed [98]. A phase II study of an anti-CXCL8 monoclonal

antibody in COPD has demonstrated safety and improvement in dyspnoea scores over 3 months[99]. In a complimentary in vitro study ELR-CXC antagonists inhibited neutrophil chemotacticfactors in the sputum of bronchiectatic patients [100]. These studies suggest that furtherinvestigation of these agents may be valuable.

Anti-TNF-a agents have an established role in treatment of systemic inflammatory diseases,including rheumatoid arthritis [101] and Crohns disease [102]. In short-term trials of anti-TNF-aagents in inflammatory lung diseases variable efficacy has been reported. While improvement inexacerbation rates in asthma have been demonstrated [103], no effect was seen in patients withCOPD [104]. The major concerns associated with the use of these agents in patients withpulmonary disease are the potential for the emergence of opportunistic infections, in particular the

re-activation of mycobacterial disease [105] and their possible association with acute deteriorationof fibrotic lung disease [106].

With the emerging array of anti-inflammatory monoclonal antibodies and targeted receptorblocker drugs, new therapeutic options will potentially become available. Carefully conductedtrials will be required to support the use and examine adverse consequences. Althoughmanipulation of the immune response is an attractive prospect for treatment of a range of

2 3 3

D . J . S M I T H

E T A L .



T a b l e 3 . R e g i s t e

r e d t r i a l s o f m a c r o l i d e t h e r a p y i n

b r o n c h i e c t a s i s

S t u d y

a c r o n y m

C o

u n t r y

D e s i g n

P o p u l a t i o n

I n c l u s i o n c r i t e r i a

D r u g

D u r a t i o n

S u b j e c t s

n

O u t c o m e

m e a s u r e s

C o m p l e t e d

B I S

I n t e r

n a t i o n a l

m u l t i c e n t r e

s

t u d y

( A u

s t r a l i a ,

N e w

Z e a l a n d )

D B R C T

( p a r a l l e l )

I n d i g e n o

u s

c h i l d r e n

( 1 – 8 y r s )

o 1 p u l m o n a r y

e x a c e r b a t i o n p r i o r

5 2 w e e k s , c o n f i r m e d

b r o n c h i e c t a s i s o r

c h r o n i c S L D


( 3 0

m g ? k g - 1 ? w e e k - 1 )

1 0 4 w e e k s

8 8

E x a c e r b a t i o n s ( t i m e t o f i r s t /

r a t e / s e v e r i t y ) , s a f e t y / a d v e r s e

e v e n t s , a n t i m i c r o b i a l

r e s i s t a n c e

R e c r u i t m e n t u n t i l

D e c 2 0 1 0

B L E S S

A u

s t r a l i a

D B R C T

( p a r a l l e l )

A d u l t s

( 1 8 – 8 0 y r s )

C o n f i r m e d

b r o n c h i e c t a s i s ( H R C T ) ,

o 2 e x a c e r b a t i o n s i n

p r i o r 5 2 w e e k s , d a i l y

p r o d u c t i v e c o u g h ,

c l i n i c a l l y s t a b l e ( 4 w e e k s )

E r t h r o m y c i n

( 4 0 0 m g b . i . d . )

4 8 w e e k s

1 1 8

E x a c e r b a t i o n r a t e , a n t i b i o t i c

u s a g e , H R Q o L , s p u t u m

v o l u m e / i n f l a m m a t o r y m a r k e r s

O n g o i n g

B A T

T h e

N e t h

e r l a n d s

D B R C T

( p a r a l l e l ) ,

s t r a t i f i e d b y

P . a e r u g i n o s a

s t a t u s

A d u l t s

( . 1 8 y r

s )

C o n f i r m e d

b r o n c h i e c t a s i s ( H R C T )


( 2 5 0 m g q . d . )

5 2 w e e k s

7 2

E x a c e r b a t i o n r a t e , c h a n g

e i n

l u n g f u n c t i o n , c h a n g e

i n

s y m p t o m

s c o r e s , c h a n g

e i n

a i r w a y m i c r o b i o l o g y , s p u

t u m

i n f l a m m a t o r y m a r k e r s

,

H R Q o L , a d v e r s e e v e n

t s

S t u d y

c o m p l e t e d ,

y e t t o r e p o r t

E M B R A C E

N e w

Z e

a l a n d

D B R C T

( p a r a l l e l )

A d u l t s ( 1

8 –

8 0 y r s )

C o n f i r m e d

b r o n c h i e c t a s i s ( H R C T ) ,

c l i n i c a l l y s t a b l e , o 1

e x a c e r b a t i o n s i n p r i o r

5 2 w e e k s


( 5 0 0 m g M W F )

2 6 w e e k s

1 4 0

E x a c e r b a t i o n s

( t i m e t o f i r s t / r a t e / s e v e r i t y ) ,

c h a n g e i n l u n g f u n c t i o

n ,

H R Q o L , c h a n g e

i n s p u t u m

c e l l c o u n t

S t u d y c o m p l e t e d ,

y e t t o r e p o r t

A u

s t r a l i a

D B R C T

( f a c t o r i a l

d e s i g n ) ,

s t r a t i f i e d

b y P .

a e r u g i n o s a

s t a t u s

A d u l t s ( 1

8 –

8 0 y r s

i n c l u d i n

g

i n d i g e n o

u s

a d u l t s )

B r o n c h i e c t a s i s ( H R C T +

c l i n i c a l ) , c l i n i c a l l y

s t a b l e , o 2 w e e k s

s i n c e a n t i b i o t i c s f o r



( 2

5 0 m g q . d . ) o r

h y p e r t o n i c s a l i n e 7 %

o r b o t h

2 6 w e e k s

1 3 0

H R Q o L , e x a c e r b a t i o n r a t e ,

c h a n g e i n l u n g f u n c t i o

n ,

c h a n g e i n s y m p t o m s s c

o r e ,

c h a n g e i n a i r w a y

m i c r o b i o l o g y , s p u t u m

i n f l a m m a t o r y m a r k e r s

,

a d v e r s e e v e n t s

R e c r u i t m e n t t o

c o m m e n c e

e a r l y 2 0 1 1

B I S : b r o n c h i e c t a s

i s i n t e r v e n t i o n s t u d y ; B L E S S : b r o n c h i e c t a s i s a n d l o w - d o s e e r y t h

r o m y c i n s t u d y ; B A T : b r o n c h i e c t a s i s a n d l o n g - t e r m

a z i t h r o m y c i n

t r e a t m e n t ; E M B R A C E :

e f f e c t i v e n e s s o f m a c r o l i d e s i n p a t i e n t s w i t h b r o n c h i e

c t a s i s u s i n g a z i t h r o m y c i n t o c o n t r o l e x a c e r b a t i o n s ; D B R C T : d o u b l e

- b l i n d r a n d o m i s e d c o n t r o l l e d t r i a l ; S L D : s u p p u r a t i v e l u n g

d i s e a s e ; H R C T : h i g h - r e s o l u t i o n c o m p u t e d t o m o g r a p h y ; b . i . d . : t w i c e d a i l y ; H R Q o L : h e

a l t h - r e l a t e d q u a l i t y o f l i f e ; q . d . : o n c e d a i l y ; P . a e r u g i n o s a : P s e u d o m o n a s a e r u g i n o s a ; M W F :

M o n d a y , W e d n e s d a y , F r i d a y .

2 3 4


T H E R A P Y



inflammatory medical conditions, history advocates caution. In March 2006, six healthy volunteers enrolled in a phase I trial were administered a first-in-man anti-CD28 humanisedmonoclonal antibody (TG1412) designed to modulate regulatory T-cells. Within hours of administration each volunteer experienced a severe cytokine storm resulting in multi-organ failure[107]. Although all six survived, the most severely affected subject required intensive care supportfor 3 weeks. Similarly, in a recent study in children and adults with CF the use of an LTB4

antagonist (BIIL284) resulted in increased respiratory exacerbations resulting in the study being

prematurely terminated after interim data analysis [108].

These studies highlight that in conditions characterised by infection associated with inflammation,anti-inflammatory therapies may be associated with adverse consequences and require very carefuland detailed analysis.

Conclusion

Evidence for the use of anti-inflammatory therapies in bronchiectasis is limited and moreadequately powered studies are required [109, 110]. There is currently insufficient evidence to

support the use of inhaled and oral corticosteroids, NSAIDs and macrolides. Individual patienttrials may be warranted for inhaled corticosteroids and macrolides and other therapies remainunproven with no evidence to support use as anti-inflammatory therapy in bronchiectasis.


None declared.

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Chapter 16

Pharmacological

airway clearance

strategies in

bronchiectasisP.T. Bye* ,#,", E.M.T. Lau* ,#," and M.R. Elkins* ,"

Summary

Impaired mucociliary clearance and mucus retention con-tribute to the chronic cycle of airway inflammation, infectionand damage in bronchiectasis. There is a strong rationale forthe use of pharmacological strategies to aid airway clearance,

often in combination with chest physiotherapy. Despite theavailability of many candidate mucoactive agents, the evidencebase for recommending these agents is currently limited.Recent research and trials have focused particularly on osmoticagents (hypertonic saline and mannitol), which increase airway hydration, and early studies appear promising for both of theseagents. Dornase alfa is not effective in non-cystic fibrosis (CF)bronchiectasis, which underscores the importance of conduct-ing high quality and adequately powered trials that specifically address the therapeutic options for non-CF bronchiectasis.

Keywords: Bronchiectasis, mucoactive, mucociliary clearance,mucus

*Dept of Respiratory and SleepMedicine, Royal Prince AlfredHospital,#Sydney Medical School, University of Sydney, Camperdown, and"Woolcock Institute of MedicalResearch, Glebe, Australia.

Correspondence: P.T. Bye, Dept of Respiratory and Sleep Medicine,Royal Prince Alfred Hospital,Missenden Road, Camperdown,NSW 2050, Australia, [email protected]


Non-cystic fibrosis (CF) bronchiectasis is a heterogeneous disorder defined by irreversibledilatation of the airways [1]. Although a wide variety of underlying pathological processes

can initiate the development of bronchiectasis, the final common pathophysiological pathway is

one characterised by the vicious cycle of chronic infection and inflammation leading to progressiveairway damage [2]. Impaired mucociliary clearance is a feature of the abnormal bronchiectacticairway [3, 4], and may represent the primary abnormality in conditions such as primary ciliary dyskinesia. Mucus retention, the result of defective mucociliary clearance, not only produces theclassic symptom of chronic productive cough but also causes airflow obstruction and ventilation/perfusion mismatch and forms a nidus for ongoing infection. Therefore, interventions aimed atpromoting clearance of excess mucus may be beneficial in patients with non-CF bronchiectasis.

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P . T .

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The normal mucociliary escalator forms an essential element of the innate host defencemechanism against inhaled pathogens. The complex physiology of mucociliary clearance in healthand disease has been reviewed in detail elsewhere [5–7]. Briefly, this process is dependent uponnormal ciliary function, optimal rheological properties of the airway mucus and an adequatevolume of airway surface liquid (ASL). The lung has the additional mechanism of cough for airway mucus clearance, although the effectiveness of cough clearance itself is also dependent upon theviscoelastic properties of mucus [8].

Agents that are intended to facilitate airway mucus clearance are termed mucoactive drugs. Aclassification of mucoactive agents, based on their mechanism of action, is summarised in table 1.Despite these agents having been available for many years, limited high-quality clinical trials havebeen undertaken exploring the efficacy of mucoactive agents in non-CF bronchiectasis. Indeed, sincethe mid-2000s, multiple authors have called for a coordinated approach in order to establishmulticentre clinical trials and for funding bodies to consider support for this disease, highlighting thehuge unmet needs in non-CF bronchiectatic therapy [9–11]. The present chapter reviews the currentpharmacological strategies available for enhancing airway clearance in non-CF bronchiectasis.

Hypertonic salineHypertonic saline is a sterile salt solution with a higher concentration of salt (typically 3–7%) thanplasma (0.9%), and is delivered by inhalation via a nebuliser. Hypertonic saline acceleratesmucociliary clearance in both healthy subjects and patients with cystic fibrosis (CF), asdemonstrated in radioaerosal studies [12–15]. It is thought to enhance airway clearance by alteringthe viscoelastic properties of mucus, increasing hydration of the ASL and also directly stimulatingcough [15–18].

The hydrating effect of hypertonic saline on mucociliary function has been best characterised inthe CF airway. In health, ASL is present as a bilayer, with a superficial mucus layer and a layer of

periciliary liquid (PCL) interposed between the mucus and the epithelium. The PCL layerapproximates the height of the cilia and provides a low-viscosity fluid in which the cilia beat [5].A critical depth of PCL is crucial for ciliary function and mucociliary transport [6]. CFtransmembrane conductance regulator dysfunction leads to airway dehydration and depletion of the PCL layer of the ASL [19]. The addition of hypertonic saline to the CF epithelium rapidly restores the depth of the ASL by creating an osmotic gradient and drawing water across the

Table 1. Common mucoactive drugs and their mechanisms of action

Agent Predominant mechanism

Expectorants

Hypertonic saline Increases airway hydration; stimulates coughMannitol

Mucolytics

N -Acetylcysteine Interrupts disulfide bonds linking mucin polymers; anti-inflammatory andantioxidant effects

Nacystelyn Interrupts disulfide bonds; increases chloride secretion

Dornase alfa Cleaves DNA polymers

Mucoregulators

Carbocisteine Modulates mucus content; anti-inflammatory and antioxidant effects

Glucocorticoids Reduces airway inflammation and mucin secretion

Macrolide antibiotics Reduces airway inflammation and mucin secretion

Anticholinergics Decreases volume of secretionsMucokinetics

b2-Agonists Increases cil ia beat frequency; improves cough clearance by increasing

expiratory flowsSurfactant Decreases mucus adherence to epithelium

Modified from [8].

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respiratory epithelium [15]. Restoration of the depth of ASL not only optimises ciliary functionbut also causes excess water entering the airway to be stored in the mucus layer, making itsrheological properties more favourable for clearance [18].

The efficacy of long-term inhalation (48 weeks) of hypertonic saline has previously beendemonstrated in a randomised placebo-controlled trial for patients with CF [20]. Regularhypertonic saline inhalation significantly improved lung function and reduced pulmonary

exacerbations. These changes were accompanied by prescription of fewer courses of antibiotics,reduction in absenteeism from school and work, and improved quality of life. A recent Cochranereview, which included 12 trials (442 participants aged 6–46 years), indicated that hypertonicsaline is a safe, low-cost and effective therapy in CF [21].

Preliminary evidence suggests that hypertonic saline may be clinically effective in non-CFbronchiectasis. In a randomised crossover trial, KELLETT et al. [22] evaluated the effect of hypertonic saline as an adjunct to physiotherapy in 24 stable bronchiectatic patients. Subjects wereallocated to receive four different single-session treatments in random order: 1) active cycle of breathing technique (ACBT) alone, 2) nebulised terbutaline followed by ACBT, 3) nebulisedterbutaline followed by isotonic saline (0.9%) and then ACBT, and 4) nebulised terbutaline

followed by hypertonic saline (7%) and then ACBT. Each single-treatment session was followed by a 1-week washout period. When hypertonic saline was used, physiotherapy yielded greater sputumweight, increased the ease of sputum expectoration and reduced sputum viscosity. Althoughencouraging, this study has clear limitations. The study only included patients who were minimalsputum producers (,10 g?day -1), a phenotype which is clearly distinct from high sputumproducers. Patient blinding was incomplete (taste masking not performed), and the results only represented the effect of a single treatment dose.

More recently, NICOLSON et al. [23] reported, in abstract form, the results of a randomised controlledtrial on the effect of long-term hypertonic saline inhalation. A total of 40 patients were randomised

to hypertonic saline (6%) or isotonic saline (0.9%) though an Aeroneb1

Go nebuliser (Aerogen,Galway, Ireland) twice daily for 12 months while performing the ACBT. The mean forced expiratory volume in 1 second (FEV1) of the study group was 83% of the predicted value. No differences inlung function, number of exacerbations or quality of life were observed at 3, 6 and 12 monthsbetween the hypertonic and isotonic saline groups. Both the hypertonic saline and isotonic salinegroups demonstrated clinically significant improvement in health-related quality of life compared tobaseline. However, this study was substantially underpowered to examine the effect of hypertonicsaline relative to isotonic saline. As clinically worthwhile benefits were not excluded by theconfidence intervals (CIs), further investigation of this promising agent is warranted.

Hypertonic saline appears to be well tolerated by patients with bronchiectasis. In 50

administrations of hypertonic saline to patients with acute exacerbations, no major bronchocon-striction (fall in FEV1 of .20%) or oxygen desaturation occurred [24]. Routine premedicationwith a bronchodilator is recommended (typically 200–400 mg salbutamol delivered via a spacerdevice). We generally recommend that spirometry is performed and oxyhaemoglobin saturationmeasured before and after delivery of the first dose.

Mannitol

Mannitol is a six-carbon monosaccharide (sugar alcohol), and is commercially available in anencapsulated stable dry powder formulation for inhalation. Similar to hypertonic saline, creation of an osmotic gradient causing influx of water into the airway and increasing the ASL layer isconsidered to be its primary mechanism of action [25]. In addition, mannitol may cause the releaseof mediators that may stimulate ciliary beat frequency [26, 27], although direct evidence thatmannitol stimulates the cilia has not been established. Mannitol may also alter the viscoelasticproperties of mucus by breaking the hydrogen bonds between mucins [28]. Mannitol (160–480 mg)increases mucociliary clearance in a dose-dependent manner in radioaerosal studies [29–31].

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In a phase-3 randomised double-blind placebo-controlled trial in CF, inhalation of mannitol (400 mgb.i.d.) for 6 months resulted in an early and sustained improvement in FEV1 compared to placebo(118 mL change from baseline to week 26; p,0.001) [32]. The benefit in FEV1 was seen irrespectiveof the concurrent use of dornase alfa. The study was not sufficiently powered to show a reduction inthe secondary end-point of exacerbations. Results from the 12-month open-label phase of the study have also been reported. The improvement in lung function with mannitol appeared to be maintainedfor up to 18 months of treatment [33]. The full results of this study are yet to be published.

There is emerging evidence that mannitol is an effective treatment in non-CF bronchiectasis. In anopen-label pilot study, DAVISKAS et al. [34] treated nine patients with bronchiectasis with 400 mgmannitol daily for 12 days. Lung function was unchanged by treatment apart from animprovement in forced expiratory flow (FEF). However, health-related quality of life hadimproved at the end of the treatment period and was maintained for 1 week thereafter. Mannitolreduced the surface tension, increased the wettability and reduced the cohesiveness and solidscontent of sputum. Cough transportability, measured by an in vitro simulated cough machine, alsoincreased. All subjects tolerated treatment well, without report of any adverse events.

A phase-3 multicentre randomised controlled trial has recently been completed and its data presented

in abstract form [35]. Subjects with bronchiectasis and mild-to-moderate lung function impairment(FEV1 of .50% pred and o1 L) were randomised to 320 mg inhaled mannitol (n5185) or placebo(n595), given twice daily for 3 months. Subjects treated with mannitol exhibited a significantreduction in the St George’s Respiratory Questionnaire total score of 3.9 units compared to 2.0 unitsin the placebo group. In the mannitol group, the time to first antibiotic use was longer and totalantibiotic use was less than for placebo. The full report of this study is awaited with interest.

Dornase alfa

Dornase alfa is a proteolytic enzyme that cleaves DNA polymers [8]. DNA is released into the

airway mucus in large amounts by degenerating neutrophils, and neutrophilic inflammation is afeature of both CF and non-CF bronchiectasis. Purulent airway secretions, particularly in CF,show an abundance of highly polymerised DNA, which contributes to mucus hyperviscosity andadhesiveness [36].

Daily inhalation of dornase alfa is a well-established therapy in CF bronchiectasis, resulting inimprovement in lung function and reduction in exacerbations, in both mild and severe disease[37–40]. In contrast, clinical studies in non-CF bronchiectasis have shown that dornase alfa is of no benefit, and may even be harmful. In a short-term study of W ILLS et al. [41], dornase alfa wasnot associated with any improvement in lung function and quality-of-life measures in patients

with non-CF bronchiectasis. Indeed in vitro sputum transportability fell following the addition of dornase alfa to non-CF bronchiectatic sputum. A subsequent international multicentre study randomised 349 patients with stable non-CF bronchiectasis to either dornase alfa or placebo over a24-week period (and remains the largest therapeutic trial in non-CF bronchiectasis to date) [42].Pulmonary exacerbations were more frequent, and FEV1 decline was greater in patients whoreceived dornase alfa.

The reasons for this difference in response between patients with CF and non-CF bronchiectasisremain unclear. The biological rationale for the use of dornase alfa in non-CF bronchiectasis wasstrong, but the unexpected detrimental finding highlights the importance of performing well-designed studies that address the therapeutic options for non-CF bronchiectasis, rather than

merely extrapolating the results of trials involving patients with CF.

N -Acetylcysteine, carbocisteine and other thiol derivatives

N -Acetylcysteine (NAC) is the classic mucolytic agent, and disrupts the disulfide bonds in mucuswhen delivered via the aerosolised route [8]. In addition to reducing sputum viscosity, NAC

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demonstrates antioxidant, anti-inflammatory and potentially antibacterial properties [43–45].NAC exhibits extremely low bioavailability, and is not readily detectable in bronchoalveolar lavagefluid following oral administration [46]. Thus the mechanism of action of oral NAC is unlikely tobe mediated via its mucolytic properties. Carbocisteine, although commonly regarded as amucolytic, has a mechanism of action that differs from that of the classical mucolytics. Mucusproduced under the action of carbocisteine shows an increase in sialomucin content. Sialomucins,which are structural components of mucus, influence the viscoelastic properties of mucus [47].

Similar to NAC, carbocisteine also exerts anti-inflammatory actions, and, in pre-clinical studies, ithas been shown to decrease levels of the cytokines interleukin (IL)-6 and IL-8 and reduceneutrophil influx into the airway lumen [48, 49].

The majority of clinical studies of NAC and thiol derivatives have been performed in chronicobstructive pulmonary disease (COPD), with conflicting results. The Bronchitis Randomized onNAC Cost–Utility Study (BRONCUS), which randomised 523 patients (Global Initiative for ChronicObstructive Lung Disease (GOLD) stage 2 and 3) to 600 mg oral NAC daily or placebo, showed thatNAC was ineffective at reducing pulmonary exacerbations and decline in lung function over a 3-yearperiod [50]. This is in contrast to the large Chinese Preventive Effects on Acute Exacerbations of COPD with Carbocisteine (PEACE) study, which randomised 709 patients (GOLD stage 2, 3 and 4)to receive carbocisteine or placebo for 1 year [51]. The primary end-point of exacerbation rate overthe 1-year period was met, with carbocisteine demonstrating a significant reduction in exacerbations(risk ratio 0.74; 95% CI 0.61–0.89). The discrepant findings between these two large randomisedcontrolled trials may have been explained by the different rates of inhaled corticosteroid usage (less inthe PEACE study) and phenotypic differences in COPD across ethnicities.

The evidence supporting the use of NAC and thiol derivative in bronchiectasis is even morelimited. There are several studies of oral and inhaled NAC in CF, but most studies have only evaluated changes in the rheologicaal properties of CF sputum [52]. The few controlled clinicalstudies in CF performed to date have consistently shown no clinical benefit [53–55].

There are currently no well-designed studies of NAC and thiol derivatives in non-CFbronchiectasis. This is supported by a Cochrane review, which concluded that there is insufficientevidence to evaluate the routine use of these agents in non-CF bronchiectasis [56].

Bronchodilators

b2-Agonists are commonly prescribed to treat airflow obstruction and bronchial hyperreactivity,and as an adjunct to physiotherapy in patients with bronchiectasis. Between 20 and 46% of patients with bronchiectasis display bronchodilator reversibility [57, 58]. b2-Agonists may

facilitate airway clearance by increasing ciliary beat frequency via stimulation of b2-receptors anddownstream increase in cyclic adenosine monophosphate (cAMP) signalling [59]. cAMP is aregulator of ciliary beat frequency in human airway epithelia [60, 61]. The bronchodilatory effectof b2-agonists may serve to increase expiratory flow rates and thus enhance cough clearance.

Two small studies have demonstrated that nebulised terbutaline, given immediately prior tophysiotherapy, yields greater sputum production [22, 62], and also improved mucociliary clearancein a radioaerosal study [62]. Although it seems reasonable and logical that b2-agonists be used totreat airflow limitation (particularly if objective bronchodilator reversibility is demonstrated), and asan adjunct to chest physiotherapy in non-CF bronchiectasis, this is currently not supported by theevidence. The relevant Cochrane reviews found no randomised controlled trials of the use of short-

acting or long-acting b2-agonists in non-CF bronchiectasis [63, 64].

Surfactant

A thin layer of airway surfactant phospholipid separates the PCL layer and the mucus gel layer,and effectively functions as a lubricant to facilitate mucus transport [8]. Furthermore, depletion of

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the PCL layer leads to entanglement and adhesion of mucus to the underlying epithelial surface.Surfactant is a potential therapeutic candidate for enhancing mucociliary clearance by reducingthe molecular interactions that bind mucus to the airway. Patients with CF display alterations inthe composition of the pulmonary surfactant system, with a reduction in the surface-activefractions, such as phosphatidylcholine and phosphatidylglycerol [65, 66]. This suggests thatsurfactant dysfunction may contribute to impaired mucociliary function in CF.

Preliminary clinical studies of exogenous surfactant therapy have only been performed in COPD andCF populations. A single randomised controlled trial of 66 patients with COPD and symptoms of chronic bronchitis showed that aerosolised surfactant for 2 weeks increased in vitro sputumtransportability, improved FEV1 and forced vital capacity (FVC) by .10%, and reduced gas-trapping[67]. The result of a phase-2 study of pulmonary surfactant in CF was recently reported in abstractform. In this placebo-controlled crossover trial, 16 subjects (aged .14 years and with an FEV1 of .40% pred) were assigned to five doses of nebulised surfactant or five doses of nebulised saline(0.9%) over a 24-hour period, with a washout period of 2 weeks. Aerosolised surfactant was welltolerated and not associated with any serious adverse events. No difference in mucociliary clearance(quantified by radioaerosal labelling) was observed between surfactant and saline (0.9%) treatment.

Humidification

Humidification is commonly used to relieve sputum retention. CONWAY et al. [68] performed asmall crossover study evaluating the role of humidification as an adjunct to chest physiotherapy inseven subjects with moderate-to-severe bronchiectasis. Humidification with cold water via a jetnebuliser for 30 minutes prior to chest physiotherapy was compared to chest physiotherapy alone.Radioaerosal clearance and sputum weight both increased when humidification was performedprior to chest physiotherapy.

In a recent study of R EA et al. [69], long-term domiciliary humidification was evaluated in arandomised placebo-controlled trial. A total of 108 subjects with COPD (n563) or bronchiectasis(n545) were randomly assigned to humidification or usual care for 12 months. Fully saturatedhumidified air at 37uC was delivered via nasal cannulae at a flow rate of 20–25 L?min-1 via ahumidifier and flow source. Patients were encouraged to use humidification for o2 hours?day -1.The primary end-point of the study, exacerbation frequency during the study period, wasnonsignificant but showed a trend favouring the humidification group (3.36 versus 2.97; p50.067).However, patients on long-term humidification therapy showed significantly fewer exacerbationdays and increased time to first exacerbation compared to usual care. Quality-of-life scores and lungfunction had also improved significantly with humidification therapy at 3 and 12 months. Theauthors hypothesised that improvement in mucociliary clearance with humidification was one of the

main mechanisms accounting for the observed benefit. The limitations of this study include theabsence of a placebo, which resulted in subjects and investigators being unblinded to theintervention assignment. The study population included both COPD and bronchiectasis, which areclearly two very distinct disorders. Compliance with therapy was poor (mean 1.6 hours?day -1), but,despite this, the secondary outcomes of the study were still significantly in favour of humidificationtherapy. The high flow rate of the humidification system was equivalent to the delivery of 1–3 cmH2O of positive end-expiratory pressure (PEEP). PEEP, even at this low pressure, may by physiologically relevant in reducing the work of breathing by offsetting intrinsic PEEP, recruitingalveolar units to improve ventilation/perfusion matching and providing partial stabilisation of theupper airway if used during sleep. Thus the mechanisms via which long-term high flow

humidification might be beneficial in obstructive airways disease remain uncertain.

Conclusion

Bronchiectasis is increasingly recognised as a major cause of respiratory morbidity. Research projectsare required in order to establish therapies for this under-investigated, under-recognised and

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undertreated disease. Such trials should focus on the experimental agent’s effects on quality of life,use of healthcare resources and participation. Hypertonic saline, NAC and carbocisteine arepromising candidates for such trials. There is proof of concept for the use of bronchodilators incombination with physiotherapy, but trials with clinically important outcome measures are needed.Mannitol appears effective, but clinicians must await publication of the full results of the most recenttrials and commercial availability of the dry powder formulation. Humidification also appearseffective. Dornase alfa has detrimental effects and should not be used in non-CF bronchiectasis.


M.R. Elkins has received financial assistance for travel to the European Cystic Fibrosis Conferencefrom Praxis Pharmaceuticals.

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a prospective randomized controlled trial. JAMA 1997; 278: 1426–1431.

68. Conway JH, Fleming JS, Perring S, et al. Humidification as an adjunct to chest physiotherapy in aiding tracheo-

bronchial clearance in patients with bronchiectasis. Respir Med 1992; 86: 109–114.

69. Rea H, McAuley S, Jayaram L, et al. The clinical utility of long-term humidification therapy in chronic airway

disease. Respir Med 2010; 104: 525–533.

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Chapter 17

Surgery for

bronchiectasisD.C. Mauchley* and J.D. Mitchell* ,#

Summary

Surgical resection for bronchiectasis should be reserved forpatients with localised disease who have failed medical

management and have persistent symptoms that negatively affect their quality of life. Patients with unilateral segmentaldisease have the best outcomes. The key to successful surgicalintervention includes: 1) complete resection of all affected areas;2) relatively early intervention to prevent development of resistant organisms and spread to adjacent lung segments; 3)pre-operative targeted antimicrobial therapy based on in vitro

sensitivities; 4) continuation of antimicrobial therapy post-operatively; 5) pre-operative nutritional supplementation when

indicated; and 6) anticipation of potential complications thatmay alter the surgical approach. Surgical resection can beaccomplished with minimal morbidity and mortality and itcan usually be completed with a video-assisted thoracoscopicapproach. The only surgical option for diffuse bronchiectasis isbilateral lung transplantation and is mainly employed whentreating patients with cystic fibrosis.

Keywords: Bronchiectasis, lobectomy, lung transplantation,pulmonary infections, segmentectomy, video-assisted thoracic

surgery

*Dept of Surgery, Division of Cardiothoracic Surgery, Section of General Thoracic Surgery and Centerfor the Surgical Treatment of Lung

Infections, University of ColoradoDenver, Aurora, and#National Jewish Health, Denver, CO,USA.

Correspondence: J.D. Mitchell,Section of Thoracic Surgery, Divisionof Cardiothoracic Surgery, C-310,University of Colorado, DenverSchool of Medicine, 12631 E. 17thAvenue, C310, Aurora, CO 80045,USA, Email [email protected]


S ince its first description by LAENNEC [1] in 1819, bronchiectasis continues to be recognised as acause of considerable respiratory illness. This disease is characterised by abnormal dilation of

bronchi and is usually the result of recurrent pulmonary infections. Patients suffer from chroniccough, excessive sputum production, a progressive decline in respiratory function and hae-moptysis that can be life threatening. The majority of patients can be treated medically, but thosethat fail or become intolerant of medical treatment may be eligible for surgical management.

Initial attempts at surgical treatment of bronchiectasis were fraught with complications. Post-operative bronchopleural fistula (BPF) and empyema occurred in f50% of cases [2, 3].Perioperative mortality was as high as 46% [3]. By 1950, the introduction of effective antibiotics inaddition to improvements in surgical technique led to a dramatic decline in perioperative morbidity and mortality. Currently, surgical intervention is mainly reserved for patients with focal disease thatremain symptomatic despite optimal medical management. Diffuse bronchiectasis may be treatedwith bilateral lung transplantation and is mainly limited to patients with cystic fibrosis (CF).

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General principles

Once thought to be in decline, the incidence of non-CF related bronchiectasis is now felt to be onthe rise in North America and throughout the world [4]. Patients present with recurrentpulmonary infections accompanied by copious sputum production and occasional bouts of haemoptysis. Traditional treatment paradigms have consisted of rotating schedules of targetedantibiotic therapy along with manoeuvres to promote secretion clearance. Surgical resection forbronchiectasis is reserved for patients who demonstrate disease progression despite optimalmedical treatment, or become intolerant of medical therapy. Failure of such treatment representsthe most common reported indication for surgical resection [5–13].

The basic concept behind surgical resection for bronchiectasis is to remove permanently damagedareas of lung parenchyma that antibiotics penetrate poorly, and thus serve as a reservoir formicrobes leading to recurrent infection. Resection of diseased segments will alter the pattern of repeated bouts of infection, and provide significant symptom relief regarding cough and excesssputum production. Patients with concomitant cavitary lung disease or recurrent bouts of haemoptysis may also benefit from surgery.

The ideal candidate for surgical therapy should have truly localised disease that is amenable toanatomic lung resection. Non-anatomic (wedge) resections should be avoided if possible as thisstrategy frequently results in incomplete removal of the affected area. Incomplete resection hasoverwhelmingly been found to be the greatest predictor of symptomatic failure in these patients[5, 7, 8, 10, 12–14]. The diseased areas of lung tend to contribute little to the patient’s overall lungfunction, thus supporting an aggressive surgical approach.

Medical therapy should always be attempted prior to entertaining the idea of surgery as the vastmajority of patients will improve. There have not been any prospective randomised trialscomparing the short- or long-term efficacy of medical treatment and surgery [15]. However,retrospective studies comparing patients requiring hospitalisation treated either medically orsurgically found that those in the surgical group were more likely to be symptom-free at the timeof follow-up. They also had fewer yearly hospital days and an overall trend toward decreasedmortality [16, 17].

Pre-operative assessment

Patients with bronchiectasis most commonly present with recurrent pulmonary infections.Symptoms associated with these infections include productive cough, foul-smelling sputum,

haemoptysis, fever and dyspnoea on exertion. The presence of a nonproductive cough issuggestive of upper lobe involvement. Adequate pulmonary reserve is determined throughstandard pre-operative pulmonary function testing and occasionally split function perfusiontesting when appropriate.

The diagnosis and location of bronchiectasis is made using standard radiographic techniques.Chest radiographs are often abnormal demonstrating focal areas of consolidation, atelectasisand occasional evidence of thickened bronchi. High-resolution computed tomography (HRCT) scanning has replaced contrast bronchography as the gold standard for radiologicdiagnosis of bronchiectasis. This imaging modality can detect the distribution of bronchiectaticalterations with only 2% false-negative and 1% false-positive rates [18]. Findings suggestive of the disease include bronchial dilation such that the internal diameter of the affected bronchusis greater than the accompanying bronchial artery, and a lack of bronchial tapering onsequential slices [4]. The extent of disease seen on HRCT scans has been correlated to quality of life and subsequent functional decline [19, 20]. The left lung is more commonly affectedthan the right and the dependent lower lobes tend to harbour more disease than the upperlobes (fig. 1). Middle lobe and lingular disease is often associated with nontuberculous

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mycobacterial disease (fig. 2). Upperlobe involvement is suggestive of CF or allergic bronchopulmonary aspergillosis.

Bronchoscopy is performed pre-operatively, primarily to identify

the offending organisms and to ruleout concomitant endobronchial pa-thology. When patients present withactive haemoptysis, bronchoscopy can be utilised to localise the sourcewithin the bronchial tree to thesegmental or even subsegmentallevel. Sputum and bronchoalveolarlavage specimens are collected toallow identification of the microbial

pathogens involved. Culture resultsshould include in vitro susceptibility testing appropriate for the culturedorganism to assist in pre-operativeantimicrobial therapy.

Many patients who have beensuffering with chronic lung infec-tions will have lost weight andcan be significantly malnourished

at presentation. If this is the case,an aggressive pre-operative regi-men of nutritional supplementa-tion is recommended. This may require the placement of a nasoje-

jeunal feeding tube or a percuta-neous gastrostomy. We have foundthat this is typically not necessary for those with limited, focal par-enchymal disease.

At our institution (National JewishHealth, Denver, CO, USA), we haveemployed a multimodality treat-ment approach where patients ap-propriate for surgical therapy arediscussed at a weekly multidisci-plinary conference attended by surgeons, pulmonologists and infec-tious disease physicians with spe-cialisation in respiratory infectiousdisease. This approach ensures thatthe patients receive the appropriateantimicrobial therapy and assists in

optimal timing of surgical intervention. In fact, the timing of resection should be dependent on thepre-operative antimicrobial regimen, allowing enough time to produce a bacterial nadir at the timeof surgery. We feel this is critical to minimise the risk profile in the perioperative period.

a)

b)

Figure 1. a) Axial and b) coronal high-resolution computed

tomography images of a patient with severe left lower lobebronchiectasis.

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Surgical technique

Anaesthesia

A standard anaesthetic techniqueutilised for thoracic surgical pro-cedures is employed. Single-lungventilation is accomplished withthe use of a double-lumen endo-tracheal tube, or rarely a singlelumen endotracheal tube with theuse of a bronchial blocker. Early lung isolation may also limit dis-persion of purulent secretions of uninvolved areas of the lungs. Athoracic epidural may be placed forpost-operative analgesia when athoracotomy is planned. This isusually not necessary in the eventof a thoracoscopic approach, wherepost-operative analgesia is providedby intercostal administration of 0.25% bupivicaine at multiple levelsplaced at the end of the procedure by the operative team. An arterial line and urinary catheter areplaced and intra-operative fluid administration is limited as with other forms of extensive lungresection. Extubation at the end of the procedure is planned.

Surgical approach

Bronchoscopy is routinely performed prior to initiation of the surgical procedure, clearing theairway of secretions to optimise ventilation during the operation. It is important to rule outbronchial obstruction secondary to a tumour or aspirated foreign body prior to attemptingresection. If severe airway inflammation is found at the time of bronchoscopy, surgical therapy may be delayed until infection control is optimised. Finally, there is always the possibility that thepatient may have normal variations in bronchial anatomy which would be helpful to know priorto attempting anatomic resection.

Surgical resection for bronchiectasis is classically approached via lateral thoracotomy, tailored forthe targeted segment or lobe. In the setting of significant disease, a full posterolateral thoracotomy may be employed. The mobilisation of muscle flaps should be accomplished at the onset of thethoracotomy, for transposition into the hemithorax later in the case after completion of theresection. An extrapleural dissection plane, if needed, may be initiated prior to placement of therib spreader.

Several important differences exist between anatomic resection for infectious lung disease andresection for malignancy. Pleural adhesions are frequently present, and in some cases can beextensive and vascular in nature. They are typically localised to the involved segment(s) of lung,but can be scattered throughout the hemithorax. In upper lobe predominant disease, theadhesions to the overlying parietal pleura can be significant. The presence of dense adhesions canbe predicted on the pre-operative HRCT, but the amount of pleural symphysis is oftenunderestimated. Pleural adhesions can usually be divided safely with a thoracoscopic approach,often with improved visibility compared with open thoracotomy. During division of denseadhesions, care must be taken to avoid adjacent vital structures such as the phrenic nerve or greatvessels.

Figure 2. Axial high-resolution computed tomography image of a

patient with right middle lobe and lingular bronchiectasis in the

setting of nontuberculous mycobacterial disease termed Lady

Windermere syndrome.

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The bronchial circulation is frequently hypertrophied in cases of longstanding bronchiectasis, andparticular care must be taken to assure haemostasis. Bronchial arteries should be ligated with clipsif enlarged. Significant lymphadenopathy is also usually present, and in the setting of chronicgranulomatous disease can make dissection at the pulmonary hilum and around vessels hazardous.When dividing pulmonary fissures with stapling devices, we advocate a line of division just on theside of the uninvolved lobe. This will assure complete resection and will avoid a staple line ininfected, devitalised tissue.

The pulmonary vessels and bronchus are divided and sealed using standard stapling devices. Oncethe resection is completed, the diseased segment or lobe should be placed in a bag for removal,unless the thoracotomy is generous enough to avoid contamination with the specimen. In thesetting of routine cases of anatomic resection for bronchiectasis, we typically do not buttress thebronchial closure with autologous tissue. The intrathoracic space is irrigated and then drainedwith one or two 28 French thoracostomy tubes. Portions of the specimen are sent for culture, andthe remainder for pathologic analysis.

Despite the fact that the majority of published series [5–10, 12, 16] of surgery for bronchiectasisdescribe resection using an open (thoracotomy) approach, a video-assisted thoracoscopic (VATS)

approach has been successfully employed in some studies, and is the preferred approach at ourinstitution [21, 22]. A standard VATS technique uses two 10-mm ports and a 4-cm utility incisioncentred over the anterior hilum. No rib spreading is used with this technique. The two 10-mmports are placed first with one in the seventh intercostal space in the anterior axillary line, and theother just posterior to the scapular tip. Once the feasibility and safety of a VATS approach areconfirmed, the utility incision is then made. We employ a wound protector for the utility incisionto avoid contamination and retract the soft tissues of the chest wall. Modifications can be made tothis technique to better serve the specifics of the planned resection. Adhesions are well visualised,and are typically easier to lyse thoracoscopically, although the presence of dense adhesions orcomplete pleural symphysis may suggest conversion to thoracotomy. The planned resection is then

completed in a manner analogous to an open approach.

Use of tissue flaps

Although not routinely performed, tissue transposition should be considered in any patient who isat increased risk for breakdown of the bronchial stump. Indications for autologous tissue coverageof the bronchial stump would include poorly controlled infection prior to surgery, resection in thesetting of significant drug resistance or in the rare case of pneumonectomy for bronchiectasis [23].We favour use of either a latissimus dorsi or intercostal muscle flap for coverage of a bronchialstump and omentum for use after a right pneumonectomy [24]. We avoid the use of a serratus

muscle flap as there tend to be problems with wound healing in these characteristically thinpatients related to the winged scapula following serratus transposition. Mobilisation of thelatissimus is performed at the initiation of the procedure, and the muscle is transposed throughthe second or third intercostal space. When using an omental flap, the omentum is mobilised via amidline laparotomy prior to thoracotomy and tacked to the undersurface of the righthemidiaphragm for retrieval later during lung resection. Occasionally, significant intrathoracicspace issues may result after resection, and may be at least partially addressed with latissimustransposition.

Post-operative managementManagement of patients after surgery for bronchiectasis is similar to that of any patient who hasundergone anatomic lung resection. Emphasis is placed on early mobilisation, aggressivepulmonary toilet, chest physiotherapy and nutritional supplementation. Chest tube managementis routine. Appropriate antimicrobial therapy is maintained in the post-operative period and isoften continued for several months, depending on the isolated organism. In patients who present

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with bilateral disease and consequently are left with unilateral disease post-operatively, bron-choscopy may be necessary to help with mobilisation and clearance of secretions. Those who aretreated with a thoracoscopic approach can leave the hospital as early as second or third post-operative day, while those who undergo thoracotomy often stay for up to a week.

Complications

The complications that accompany lung resection for bronchiectasis mirror those that follow lungresection for other indications with a few exceptions. Overall morbidity following resection rangesfrom 9% to 25% depending on the series. The most common complications after surgery forbronchiectasis include atelectasis requiring therapeutic bronchoscopy, prolonged air leak, spaceproblems, empyema, BPF and wound infection (table 1) [5, 7–13, 22]. Absence of pre-operativebronchoscopy, forced expiratory volume in 1 second of ,60% of the predicted value andincomplete resection have all been associated with the development of post-operativecomplications [25].

Although it is rare, the development of BPF is a source of significant morbidity, particularly

after pneumonectomy. It occurs more commonly on the right side, after completionpneumonectomy, and in the setting of patients who have persistently positive sputum culturesfor organisms such as multidrug-resistant Mycobacterium tuberculosis [22, 24]. When presentedwith a patient at high risk of development of BPF, prevention is paramount. Appropriateantimicrobial coverage should be given before surgery; a tension-free technique used to closethe bronchus and muscle or omentum used to buttress the closure. Typical findings of a BPFafter pneumonectomy include fever, cough productive of serous followed by purulent sputum,contralateral lung infiltrates and a dropping air–fluid level on chest radiograph. Managementbegins with prompt drainage of the infected space to prevent further damage to the remaininglung. If the BPF is diagnosed very early after resection, primary repair of the bronchial stump

with rebuttressing may be attempted. When diagnosis is delayed management usually requiresrib resection and creation of an Eloesser flap followed by BPF closure and subsequent Clagettprocedure.

As mentioned previously, intrathoracic space problems are somewhat more common after surgery for bronchiectasis, mainly due to the fact that the remaining lung is often unable to fully expand.This leaves residual space that is usually not a problem, but can lead to development of empyemain cases that involve significant pleural soilage or parenchymal injury. Again, prevention is key andpatients with these potential problems should be anticipated. Liberal use of muscle flaps tominimise the space can help prevent complications.

Table 1. Summary of morbidity after surgical resection for bronchiectasis

First author

[ref.]

Prolonged air

leak/space

issues

Atelectasis Empyema/

BPF

Wound

infection

Bleeding Arrhythmia Overall

morbidity

DOGAN [9] 0 1.4 1.8 7.4 0 0 10.6 A GASTHIAN [5] 4.5 6.7 4.5 0 3 2.2 24.6

FUJIMOTO [10] 5.6 6.7 6.7 0 1.1 0 19.6

PRIETO [13] 5.9 0 0 0 3.4 3.4 12.6

K UTLAY [12] 1.7 2.3 1.2 0 1.7 0 11.4B ALKANLI [8] 2.5 2.9 1.7 0 1.7 0 8.8

GURSOY [11] 9.8 3.2 0 3.3 0 0 16.3

B AGHERI [7] 3.2 3.6 3.2 5.7 0 0 15.8ZHANG [22] 2.7 2 1 0 1.1 4 16.2

Data are presented as % of all patients in each reference. BPF: bronchopleural fistula.

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chronic lung infection. The mortality rate was 0%, morbidity rate was 18.7% and 12 (15.3%) cases

were converted to open procedure. Reasons for conversion to open procedure included denseadhesive disease as well as upper lobe-predominant disease. Compared with those who underwentopen thoracotomy during the same time period, patients undergoing VATS resection sufferedfewer post-operative complications, had less blood loss and a shorter hospital stay. More recently,ZHANG et al. [27] reported 52 patients who underwent VATS lobectomy using two 12-mm trocarsand a 4–5-cm incision. Overall, they had similar findings with no mortality, a morbidity rate of 15.4% and conversion to thoracotomy in 13.5% of patients. Furthermore, those who were treatedwith a VATS approach had less morbidity and a shorter hospital stay compared with a cohort of patients who underwent open thoracotomy for resection during the same time period. Pain scoresbased on an 11 point pain scale were also lower in the VATS group. The conclusions of both

reports were that benign lung disease, including bronchiectasis, could feasibly be resected using aVATS approach with negligible mortality and lower morbidity than with thoracotomy.

Lung transplantation

Lung transplantation in patients with bronchiectasis is only indicated for those with diffuse diseasethat is not amenable to segmental surgical resection and declining lung function despite maximalmedical therapy. The vast majority of transplants for bronchiectasis are performed on patients withCF. Bronchiectasis develops in nearly all cases of CF and leads to chronic cough, expectoration of abnormal mucus, progressive airflow obstruction and persistent respiratory tract infections. Thosewith advanced bronchiectasis have poor quality of life and are at increased risk of death secondary todeclining lung function. Lung transplantation has been shown to both improve quality of life andprolong survival in appropriately selected patients with advanced bronchiectasis [28, 29].

CF is the third most common indication for which lung transplantation is performed [30]. Thecurrent recommendation is for bilateral lung transplant in those with suppurative lung diseasesecondary to CF, even in those with heterogeneous disease. Single lung transplantation would risk contamination of the new graft by the old lung in an immunocompromised patient. Some centreswill perform a single lung transplant in conjunction with contralateral pneumonectomy to avoidthis risk.

The guidelines for referral of patients with CF and bronchiectasis for transplantation are listed intable 5 [30]. Additionally, patients should be considered for transplantation if there is a ,50%likelihood of survival over 2 years without transplant, if quality of life is likely to be improved as aresult of transplant, there are no contraindications to transplant, and they are informed of the risksand benefits of the operation and committed to proceeding with evaluation and listing. Youngfemales with CF are considered for early referral if they suffer rapid deterioration in pulmonary

Table 4. Summary of pulmonary symptoms after surgical resection for bronchiectasis

First author

[ref.]

Mean follow-up

time years

% Follow-up Asymptomatic Symptomatic

improvement

No change in

symptoms/worse

DOGAN [9] 4.6 Not stated 71 Not stated Not stated A GASTHIAN [5] 6 76.9 45.5 22.4 9 A SHOUR [6] 3.8 100 74.1 22.4 3.5

FUJIMOTO [10] 6.1 87.8 40 33.3 14.5PRIETO [13] 4.5 90.8 61.3 26.1 3.4K UTLAY [12] 4.2 89.2 66.9 18.7 3.6

B ALKANLI [8] 0.75 96.2 79.4 12.2 4.6GURSOY [11] 1.3 81.5 68.5 8.7 4.3B AGHERI [7] 4.5 100 68.5 23.8 7.5ZHANG [22] 4.2 89.4 60.5 14.1 14.8

Data are presented as % of all patients (including those lost to follow-up) from each reference, unless otherwise

stated.

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status as they have a particularly poor prognosis [30]. Finally, several studies in the 1990sdescribed infection with Burkholderia cepacia in prospective CF transplant candidates to beassociated with significant post-transplantation infectious complications and poor outcomes

[31, 32]. This has led to the presence of B. cepacia infection to be a relative contraindicationto lung transplantation in the CF population, although some centres continue to offertransplantation therapy in this setting. More recent evidence suggests that some, but not allsubspecies within the B. cepacia complex confer an increased risk [33].

A number of complications may occur after lung transplantation for CF and bronchiectasis,including haemorrhage, pulmonary oedema, primary graft dysfunction, anastomotic dehiscence andvarious infectious complications. Bacterial infections are common after transplant for bronchiectasisas numerous pathogens chronically dwell in respiratory tract secretions of these patients. Anti-bacterial regimens guided by pre- and perioperative cultures are used post-operatively in addition tostandard prophylactic medications given for viral and fungal pathogens [34].

Patients with CF and bronchiectasis can expect a dramatic improvement in pulmonary functionafter lung transplant as well as the ability to perform activities of daily living without limitations.Long-term survival has been demonstrated in a review of 123 patients with CF who underwenteither bilateral lung transplantation or bilateral lower lobe transplant from living donors [35].Survival rates were 81% at 1 year, 59% at 5 years and 38% at 10 years. A sustained improvementin quality of life after transplantation can be expected for at least 1–3 years [34].

Transplantation for non-CF bronchiectasis is rare and specific referral guidelines have not beendeveloped. For this reason, the guidelines used for those with CF bronchiectasis are generally used [30].


None declared.

References1. Laennec RTH. De l’Ausculation Mediate ou Traite du Diagnostics des Maladies des Poumons et du Coeur. [On

Mediate Ausculation or Treatise on the Diagnosis of the Disease of the Lungs and Heart]. Paris, Brosson and

Chaude, 1819.

2. Lindskog GE, Hubbell DS. An analysis of 215 cases of bronchiectasis. Surg Gynecol Obstet 1955; 100: 643–650.

3. Ochsner A, DeBakey M, DeCamp PT. Bronchiectasis; its curative treatment by pulmonary resection; an analysis of 96 cases. Surgery 1949; 25: 518–532.

4. O’Donnell AE. Bronchiectasis. Chest 2008; 134: 815–823.

5. Agasthian T, Deschamps C, Trastek VF, et al. Surgical management of bronchiectasis. Ann Thorac Surg 1996; 62:

976–978.

6. Ashour M, Al-Kattan K, Rafay MA, et al. Current surgical therapy for bronchiectasis. World J Surg 1999; 23:

1096–1104.

Table 5. Guidelines for lung transplantation in diffuse bronchiectasis (both cystic fibrosis and non-cystic

fibrosis)

Guidelines for referral to

a transplant centre

FEV 1 ,30% predicted or a rapid decline in FEV 1, particularly

in young female patientsExacerbation of pulmonary disease requiring ICU stay

Increasing frequency of exacerbations requiring antibiotic therapy

Refractory and/or recurrent pneumothorax

Recurrent haemoptysis not controlled by embolisationGuidelines for transplantation Progressive decline in lung function

Oxygen-dependent respiratory failure

HypercapniaPulmonary hypertension

FEV 1: forced expiratory volume in 1 second; ICU: intensive care unit.

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7. Bagheri R, Haghi SZ, Fattahi Masoum SH, et al. Surgical management of bronchiectasis: analysis of 277 patients.

Thorac Cardiovasc Surg 2010; 58: 291–294.

8. Balkanli K, Genc O, Dakak M, et al. Surgical management of bronchiectasis: analysis and short-term results in 238

patients. Eur J Cardiothorac Surg 2003; 24: 699–702.

9. Dogan R, Alp M, Kaya S, et al. Surgical treatment of bronchiectasis: a collective review of 487 cases. Thorac

Cardiovasc Surg 1989; 37: 183–186.

10. Fujimoto T, Hillejan L, Stamatis G. Current strategy for surgical management of bronchiectasis. Ann Thorac Surg

2001; 72: 1711–1715.

11. Gursoy S, Ozturk AA, Ucvet A, et al. Surgical management of bronchiectasis: the indications and outcomes. Surg

Today 2010; 40: 26–30.

12. Kutlay H, Cangir AK, Enon S, et al. Surgical treatment in bronchiectasis: analysis of 166 patients. Eur J

Cardiothorac Surg 2002; 21: 634–637.

13. Prieto D, Bernardo J, Matos MJ, et al. Surgery for bronchiectasis. Eur J Cardiothorac Surg 2001; 20: 19–23.

14. Stephen T, Thankachen R, Madhu AP, et al. Surgical results in bronchiectasis: analysis of 149 patients. Asian

Cardiovasc Thorac Ann 2007; 15: 290–296.

15. Corless JA, Warburton CJ. Surgery vs non-surgical treatment for bronchiectasis. Cochrane Database Syst Rev 2000;

4: CD002180.

16. Annest LS, Kratz JM, Crawford FA Jr. Current results of treatment of bronchiectasis. J Thorac Cardiovasc Surg

1982; 83: 546–550.

17. Sanderson JM, Kennedy MC, Johnson MF, et al. Bronchiectasis: results of surgical and conservative management.

A review of 393 cases. Thorax 1974; 29: 407–416.

18. Young K, Aspestrand F, Kolbenstvedt A. High resolution CT and bronchography in the assessment of

bronchiectasis. Acta Radiol 1991; 32: 439–441.

19. Eshed I, Minski I, Katz R, et al. Bronchiectasis: correlation of high-resolution CT findings with health-related

quality of life. Clin Radiol 2007; 62: 152–159.

20. Sheehan RE, Wells AU, Copley SJ, et al. A comparison of serial computed tomography and functional change in


21. Mitchell JD, Bishop A, Cafaro A, et al. Anatomic lung resection for nontuberculous mycobacterial disease. Ann

Thorac Surg 2008; 85: 1887–1892.

22. Zhang P, Jiang G, Ding J, et al. Surgical treatment of bronchiectasis: a retrospective analysis of 790 patients. Ann

Thorac Surg 2010; 90: 246–250.

23. Shiraishi Y, Nakajima Y, Katsuragi N, et al. Pneumonectomy for nontuberculous mycobacterial infections. Ann Thorac

Surg 2004; 78: 399–403.

24. Sherwood JT, Mitchell JD, Pomerantz M. Completion pneumonectomy for chronic mycobacterial disease. J Thorac Cardiovasc Surg 2005; 129: 1258–1265.

25. Eren S, Esme H, Avci A. Risk factors affecting outcome and morbidity in the surgical management of

bronchiectasis. J Thorac Cardiovasc Surg 2007; 134: 392–398.

26. Weber A, Stammberger U, Inci I, et al. Thoracoscopic lobectomy for benign disease – a single centre study on 64

cases. Eur J Cardiothorac Surg 2001; 20: 443–448.

27. Zhang P, Zhang F, Jiang S, et al. Video-assisted thoracic surgery for bronchiectasis. Ann Thorac Surg 2011; 91:

239–243.

28. Courtney JM, Kelly MG, Watt A, et al. Quality of life and inflammation in exacerbations of bronchiectasis. Chron

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30. Orens JB, Estenne M, Arcasoy S, et al. International guidelines for the selection of lung transplant candidates: 2006update – a consensus report from the Pulmonary Scientific Council of the International Society for Heart and

Lung Transplantation. J Heart Lung Transplant 2006; 25: 745–755.

31. Egan JJ, McNeil K, Bookless B, et al. Post-transplantation survival of cystic fibrosis patients infected with

Pseudomonas cepacia . Lancet 1994; 344: 552–553.

32. Snell GI, de Hoyos A, Krajden M, et al. Pseudomonas cepacia in lung transplant recipients with cystic fibrosis. Chest

1993; 103: 466–471.

33. Murray S, Charbeneau J, Marshall BC, et al. Impact of burkholderia infection on lung transplantation in cystic

fibrosis. Am J Respir Crit Care Med 2008; 178: 363–371.

34. Hayes D Jr, Meyer KC. Lung transplantation for advanced bronchiectasis. Semin Respir Crit Care Med 2010; 31:

123–138.

35. Egan TM, Detterbeck FC, Mill MR, et al. Long term results of lung transplantation for cystic fibrosis. Eur J

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Chapter 18

Conclusions andfuture developmentsR.A. Floto

Correspondence: R.A. Floto, Cambridge Institute for Medical Research, University of Cambridge, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0XY, UK, Email: [email protected]

This Monograph represents a ‘‘state-of-the-art’’ review of non-cystic fibrosis (CF)bronchiectasis and highlights many recent advances in our understanding of this condition

and how best to manage it. However, it is clear, that many important unanswered questionsremain about the patho-physiology, investigation and treatment of bronchiectasis. The man-agement of these patients remains hampered by a paucity of clinical trial evidence which, throughnecessity, requires us to draw on potentially misleading data from CF or chronic obstructivepulmonary disease studies. Furthermore, inadequate education and training of physicians remainbarriers to optimal delivery of care to patients with non-CF bronchiectasis, something which thisMonograph may hopefully begin to address.

There are a number of potential future developments, discussed below, which may significantly contribute to our understanding of why non-CF bronchiectasis develops in particular in-dividuals, how to best investigate possible aetiological factors and how to optimally manage thesepatients.

Why does bronchiectasis develop?

As described in the chapter by BILTON and JONES [1], a large number of conditions leading toimpaired host immunity and/or defective muco-ciliary clearance have been implicated in thedevelopment of non-CF bronchiectasis. However, using established investigative approaches,

outlined by DRAIN and ELBORN [2], we are currently unable to define an obvious triggering cause ina large percentage of adults with bronchiectasis.

Immunity and inflammation

Developments in our understanding of the mechanisms controlling lung inflammatory andimmune responses [3] and their resultant effects on lung tissue [4] may allow researchers to focuson specific critical host responses that may qualitatively or quantitatively vary within a populationpredisposing particular individuals to bronchiectatic lung damage. Future developments inimmunological testing [2, 5] may focus on identifying aberrant responses in patients’ immune

cells to inflammatory or infective stimuli. Furthermore, more detailed analysis of patients withbronchiectasis associated with inflammatory bowel disease [6] and systemic autoimmunity [7]may provide important insights into how aberrant immunological responses might lead tobronchiectasis.

Eur Respir Mon 2011. 52, 258–261. Printed in UK – all rights reserved, Copyright ERS 2011. European Respiratory Monograph; ISSN: 1025-448x. DOI: 10.1183/1025448x.10004810

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Microbiology

A better understanding of the role of bacteria and how they interact with epithelial cellsand viruses [8] is likely to permit more targeted treatments and more effective prophylaxis.Nonculture-based microbial detection methods [9] are likely to provide mechanistic insights intothe possible protective role of commensal microbial flora, the role of anaerobic and intracellularorganisms and the dynamic interplay between bacterial species in specific lung niches. For fungal

diseases [10] and nontuberculous mycobacterial infection [11], future research into the basicmechanisms of disease may permit development of novel diagnostic tools and more effectivetreatment strategies.

Mucociliary clearance

Recent work has suggested that nonclassical or secondary ciliary dysfunction [12] and epithelialchannel mutations [13] may be important determinants in compromising mucociliary clearance(MCC) and, thus, predisposing to bronchiectatic damage. Novel developments in lung imag-ing [14], including quantification of global and regional MCC, may permit more detailed

investigation of bronchiectasis patients and assessment of the impact of specific physiotherapy techniques and mucolytic therapies.

Novel genetic approaches

There are potentially three ways in which new developments in genetics might be exploited tobetter understand the patho-physiology of non-CF bronchiectasis.

1) Genome-wide association scans (GWAS) may, as in other conditions [15], identify noveldisease-associated, single-nucleotide polymorphisms and potentially uncover critical pathwaysinvolved in bronchiectasis in an unbiased, ‘‘hypothesis-free’’ way. Challenges in undertaking

GWAS studies include the large number of patient DNA samples required (usually severalthousand), as well as the problem of multiple initiators for the development of bronchiectasisleading to reduced signal discrimination.

2) Candidate gene approaches could also be used to identify diseased-associated polymorphisms inmore well defined subsets of patients. Obvious candidates would include known genetic modifiersof CF [16], genes involved in lung inflammation and those encoding proteins that are critical forepithelial cell function.

3) Whole exome analysis using massive parallel sequencing can now permit rapid sequencingof the entire expressed genome of individuals [17], potentially permitting detection of gene

mutations in small cohorts of patients with familial disease.

Can we improve the treatment of patients with non-CFbronchiectasis?

It is reasonable to anticipate a number of future developments which may impact on themanagement of patients with non-CF bronchiectasis.

New antibiotic strategies

As highlighted in the chapter by HAWORTH [18], the development of new nebulised or inhaledformulations of single or combination antibiotics may significantly impact on our ability toprovide adequate prophylaxis for patients. In addition, a number of novel approaches are beingdeveloped for the treatment of Pseudomonas aeruginosa which may prove useful, including novelb-lactamase inhibitors, blockers of bacterial efflux pumps (which normally remove otherwise toxicantibiotics), antimicrobial peptides and species-specific bacteriophage-based therapy [19].

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Novel anti inflammatory agents

As discussed in the chapter by SMITH et al. [20], anti-inflammatory therapy may be of considerablebenefit in bronchiectasis. Novel agents that may have a future role include nonantibiotic macrolides,HMG-CoA inhibitors (statins) and peroxisome proliferator-activated receptor-c agonists. Thedifficulty will be to balance control of inflammation with compromise of host defence.

Mucolytic strategies

The potential benefits of improved airway clearance [21] are likely to be vast. Future therapies thatreduce mucus viscosity (by altering mucin production or blocking subsequent cross-linking),increase airway-surface liquid (through osmosis or altered epithelial channel activity) or improveciliary function may all have potential benefit.

Surgery and lung repair

More research will be needed to define the precise role of surgery in the management of non-CF

bronchiectasis [22]. Anticipated improvement in surgical techniques and reductions in peri-operative morbidity will impact on when surgery in considered and in whom. Futuredevelopments in stem cell biology (including studies re-programming induced pluripotent stemcells and overcoming engraftment difficulties) may open the door for therapeutic lung repair andregeneration.

Over the next few years we can optimistically look forward to greater advances in our understandingof the patho-physiology and genetic determinants of non-CF bronchiectasis, the development of more sophisticated methods for investigation of patients and an increasing number of clinical trialsfocusing on improving evidence-based treatment of this challenging condition.


None declared.

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3. Lambrecht BN, Neyt K, GeurtsvanKessel CH. Pulmonary defence mechanisms and inflammatory pathways in

bronchiectasis. Eur Respir Mon 2011; 52: 11–21.

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