LOWER RESPIRATORY TRACT INFECTIONS

Prof T Rogers

PNEUMONIA

THE IMPORTANCE OF PNEUMONIA

• A major killer in both developed and developing countries

• Accounts for more deaths than other infectious diseases

• Mortality rates vary but can be as high as 25%

• A major cause of death in children in developing countries

• Incidence here (?) 2-5/1000 population

PNEUMONIA

• Neither radiological or microbiological criteria are specific for predicting the cause of pneumonia

• A better approach is to first consider the clinical circumstances under which pneumonia acquired

• Add the clinical background of the particular patient…

Classification of pneumonia

• Community-acquired

• Hospital-acquired

• Aspiration and anaerobic

• Pneumonia in immunocompromised

• AIDS-related

• Geographically restricted

• Recurrent

COMMUNITY-ACQUIRED PNEUMONIA: INTRODUCTORY POINTS

• More common at the extremes of age

• Twice as common in winter months

• A General Practitioner is likely to see up to 10 cases per yr

• Represent <10% of all respiratory infection cases prescribed antibiotics

• Most will be managed in the community

TYPES OF COMMUNITY ACQUIRED PNEUMONIA

• In a previously healthy individual

• Here the infection may have been acquired by droplet spread from another

• Alternatively, in patients with underlying diseases endogenous colonizing bacteria may be the cause

• These are more likely to be resistant to first-line antibiotics

SYMPTOMS OF PATIENTS WITH COMMUNITY-ACQUIRED PNEUMONIA(%)

[Mc Farlane unpublished]

• Cough 92• Fever 86• Breathlessness 67• Pleural pain 62• Headache 55• New sputum production 54• Muscle aches 44• Nausea/vomiting 48

COMMUNITY ACQUIRED PNEUMONIA: WHAT’S CAUSING IT?

MICROBIOLOGICAL CAUSES (%) OF COMMUNITY ACQUIRED PNEUMONIA FROM

HOSPITAL BASED STUDIES (N=3,000)CAP

Severe CAP

• No cause found 36 33• Pneumococcus 25 27• Influenza virus 8 2.3• Legionella spp*. 7 17• Haem. Influenzae 5 5• Other viruses 5 8• Psittacosis/Q fever 3 2• Gram neg. bacilli 2.7 2• Staph aureus* 2 5

INVESTIGATIONS FOR DIAGNOSIS OF PNEUMONIA

• Non-invasive: blood count, urea, albumin,LFT’s, sputum gram, chest X-ray, CT scan

• Culture of sputum, blood, pleural fluid

• Serology: pneumococcal, Legionella antigen

• Invasive: induced sputum, bronchoscopy, open lung biopsy

TYPICAL GRAM APPEARANCE OF Strep pneumoniae IN SPUTUM

GRAM POSITIVE CHAINSDIPLOCOCCI

Streptococcus pneumoniae (pneumococcus)

• A gram positive coccus that grows in short chains

• Alpha haemolytic on blood agar

• Identified by its susceptibility to optochin

• Polysaccharide capsule confers pathogenicity-at least 80 serotypes

• There are multivalent vaccines for prevention of pneumococcal disease

SOME COMPLICATIONS OF PNEUMOCOCCAL SEPSIS

• Bacteraemia (10%+)

• Empyema (1%)

• Meningitis (<0.5%)

• Mortality rates of 10-25%

• Splenectomy or asplenia a major risk factor

Pneumococcal vaccine is recommended for:

• Age >65 years

• Underlying chronic lung disease

• Asplenia

• Alcoholism

• Diabetes mellitus

• Chronic renal failure

• HIV infection

BTS Guidelinesfor the Management of Community Acquired

Pneumonia in Adults Updated 2004

www.brit-thoracic.org/guidelines

Treatment

• Home treated-Amoxicillin 500mg or 1 g tds PO (or admitted for social reasons)

• Hospital treated Amoxicillin 500mg or 1 g PO plus erythromycin 500mg qds po

• Hospital treated severe Co-amoxiclav 1.2 g tds and erythromycin 500mg qds I/v , +/- rifampicin

VIRUSES THAT CAUSE COMMUNTIY ACQUIRED PNEUMONIA

INFLUENZA

OTHER VIRAL CAUSES

• Respiratory syncytial virus (RSV)

• Parainfluenza viruses

• Enteroviruses

• (Cytomegalovirus)

CAUSES OF ‘ATYPICAL’ PNEUMONIA

• Mycoplasma pneumoniae

• Chlamydia pneumoniae

• Legionella pneumophila

• Coxiella burnetii

Mycoplasma pneumoniae

• Has no cell wall, therefore doesn’t respond to beta lactams

• Causes atypical pneumonia in adolescents and young adults

• Dry hacking cough, low grade fever, headache feature

• Isolation by culture of the organism is difficult therefore diagnosis is confirmed by a high CFT or rising titre of specific antibodies

• Cold agglutinins also typical• Macrolides or tetracyclines most active

Chlamydia pneumoniae

• An obligate intracellular bacterium

• Causes mild pneumonia but may cause protracted symptoms

• Sore throat, hoarseness, URT symptoms feature

• Serological diagnosis rather than culture

• Tetracyclines, macrolides, quinolones active

Legionnaires’ disease

• A severe pneumonia due to Legionella pneumophila

• Can be community or hospital acquired

• Organism is acquired from environmental sources eg, humidified air conditioning, showers

• Usually attacks debilitated individuals

RISK FACTORS

• Male sex

• Advanced age

• Cigarette smokers

• Alcoholism

• Chronic lung disease

• Immmunosuppression, malignancy

Legionnaires’ disease

• Hyponatremia, confusion, nausea, vomiting, abnormal LFT’s a feature

• Diagnosis often confirmed by urinary antigen test (specific for serogroup 1)

• Can be cultured on special media• Must be notified to Public Health as it can

cause outbreaks• Most active antibiotics are: macrolides,

quinolones, rifampicin

Antibiotic Treatment of Community Acquired Pneumonia

• The priority is to cover pneumococcus

• Penicillin, amoxycillin, cephalosporins, new quinolones and macrolides have all been used as monotherapy

• Choice will be influenced by local resistance rates for pneumococcus

Examples of antibiotics for CAI

• Benzylpenicillin

• Penicillin V

• Ampicillin, amoxycillin, Augmentin

• Cefuroxime, cefotaxime, ceftriaxone

• Moxifloxacin (a quinolone)

• Erythromycin, clarythromycin, azithromycin

PATHOGEN PREFERRED THERAPY

S pneumoniae amoxicillin 500 mg – 1.0 ga tds po or benzylpenicillin 1.2 g qds iv

M pneumoniae

C pneumoniae

erythromycin 500 mg qds po or iv or

clarithromycin 500 mg bd po or iv

C psittaci/C burnetii

tetracycline 250 mg – 500 mg qds po or

500 mg bd iv

Legionella spp.

clarithromycin 500 mg bd po or iv

± rifampicin c 600 mg od or bd, po/ iv

Hinfluenzae

Non- B-lactamase-producing: amoxicillin 500 mg tds po or ampicillin 500 mg qds iv

B-lactamase-producing: co-amoxiclav 625 mg tds po or 1.2 gtds iv

Gram negative enteric bacilli

cefuroxime 1.5 g tds or

cefotaxime 1-2g tds iv or ceftriaxone 2g

od iv (Comment: the table in the 2001

version incorrectly stated bd)

P.aeruginosa

ceftazidime 2g tds iv plus gentamicin or

tobramycin (dose monitoring)

S.aureus Non-MRSA: flucloxacillin 1-2gqds iv

±rifampicin 600 mg od or bd, po/iv

MRSA: vancomycin 1gbd iv (dose monitoring)

ACID ALCOHOL FAST RODS SUGGESTING TUBERCULOSIS

KLEBSIELLA PNEUMONIA (RARE)

COMMUNITY ACQUIRED PNEUMONIA IN INFANTS AND CHILDREN

• Group B streptococcus and E coli cause pneumonia in neonates

• RSV an important pathogen in infants

• Bordetella pertussis (cause of whooping cough) important in young children

• As is Haemophilus influenzae type b

SOME FEATURES OF NOSOCOMIAL PNEUMONIA

• Often ventilator associated, therefore seen in ITU most commonly

• Due to both endogenous organisms and others acquired by cross infection

• MRSA, gram negatives predominate

• High associated mortality because of co-morbidity and antibiotic resistance

HOSPITAL ACQUIRED PNEUMONIA: Pseudomonas aeruginosa

TREATMENT OF HOSPITAL ACQUIRED PNEUMONIA

• Will depend on the local epidemiology of the unit/hospital

• Often require good cover for MRSA and gram negative enterobacteria

• Therefore vancomycin and carbapenem or Tazocin may be used

PNEUMONIA IN THE IMMUNOCOMPROMISED HOST

• Cause depends on the underlying immunodeficiency

• More likely to present as a diffuse interstitial pneumonia

• Treatment often empirical as establishing the cause is often difficult

MAJOR CAUSES OF PNEUMONIA IN IMMUNOCOMPROMISED

• Pneumocystis jiroveci (carinii)

• Cytomegalovirus

• Other respiratory viruses

• Tuberculosis

• Fungi

Pneumocystis jiroveci(Lung biopsy)

Cyst stage

NOCARDIOSIS(Cause: Nocardia asteroides, acid fast rod)

Geographically restricted pneumonias

• Typhoid

• Melioidosis

• Brucellosis

• Endemic mycoses: histoplasmosis

• Helminthic: paragonimiasis

Recurrent pneumonia

• May be caused by local bronchial or pulmonary abnormality

• Obstruction due to eg, foreign body, carcinoma, lymph node

• Chronic obstructive lung disease: bronchiectasis• Neurological disorders: motor neurone disease• Structural: tracheo-oesophageal fistula• Aspiration (alcoholics): anaerobic organisms• Immunodeficiency state:

hypogammaglobulinaemia

EMPYEMA

• May arise as an acute complication of pneumonia• Characterised by collection in pleural cavity, malaise,

fever, pleuritic pain, leucocytosis• Chronic empyema usually occurs after failure to

diagnose or treat adequately an acute empyema• May be loculated, or associated with a broncho-pleural

fistula• Organisms are those causing the original pneumonia, or

anaerobes• Treat by drainage of the collection and antibiotics after

microbiological findings