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MEDICALLY IMPORTANT MEDICALLY IMPORTANT FUNGI and ANTIFUNGAL FUNGI and ANTIFUNGAL
THERAPYTHERAPY
DR. BREIDA BOYLE
INTRODUCTIONINTRODUCTION
Fungi are a diverse group of sacrophytic and parasitic eukaryotic organisms
Kingdom: Mycota Of 100,000 fungal species only 100 have
pathogenic potential for humans, only a few account for clinically important infections
Mycoses : Human Fungal Diseases Fungal spores may be important as human
allergenic agents
INTRODUCTIONINTRODUCTION
MYCOSESMUCOSAL: limited to mucosaeCUTANEOUS: limited to the dermisSUBCUTANEOUS : when infection
penetrates significantly beneath the skinSYSTEMIC : when the infection is deep
within the body or disseminated to internal organs
PATHOGENIC FUNGIPATHOGENIC FUNGI
TRUE PATHOGENS
OPPORTUNISTICPATHOGENS
TRUE PATHOGENSTRUE PATHOGENS
Epidermophyton speciesMicrosporum speciesTrichophyton species
Actinomadura maduraeCladosporium
Madurella griseaPhialophora
Sporothrix schenckii
Blastomyces dermatitidis Coccidioides immitis
Histoplasma capsulatumParacoccidioides brasiliensis
Cutaneous infective agents Subcutaneous infective agents
Systemic infective agents
OPPORTUNISTIC OPPORTUNISTIC PATHOGENSPATHOGENS
Absidia corymbiferaAspergillus fumigatus
Candida albicansCrytococcus neoformans
Pneumocystis cariniiRhizomucor pusillus
Rhizopus oryzae (R.arrhizus)
PATHOGENIC FUNGIPATHOGENIC FUNGI
TRUE PATHOGENS
OPPORTUNISTICPATHOGENS
CLASSIFICATION OF FUNGICLASSIFICATION OF FUNGI
Depends on :Characteristic StructuresHabitatsModes of Growth Modes of ReproductionClinical SettingDNA Homology
Cell Wall and MembraneCell Wall and Membrane
Composed mainly of chitin rather than peptidoglycan (bacteria)-so unaffected by antibiotics
Cell Wall also has glucans and Mannans Chitin: consists of a polymer of N-
acetylglucosamine Fungal Membrane contains ergosterol rather than
cholesterol found in mammalian cells, use in antifungal agents such as amphotericin which binds to ergosterolpores that disrupts membrane function cell death
Cell MembraneCell Membrane
The imidazole antifungal drugs ( clotrimazole, ketoconazole, miconazole) and the triazole antifungal agents (fluconazole , itraconazole, voriconazole) interact with the C-14 α-demethylase to block demethylation of lansterol to ergosterol, vital component of cell membrane and disruption of it`s synthesis results in death
HABITATHABITAT
All fungi are heterotrophs ( their require some form of organic carbon for growth)
They depend on transport of soluble nutrients across their cell membrane
To do this they secrete degradative enzymes ( proteases etc) into their immediate environment, therefore they live on dead organic material
So Natural Habitat : is soil or water containing decaying organic matter
MODES OF FUNGAL MODES OF FUNGAL GROWTHGROWTH
FILAMENTOUSMOLDS
UNICELLULARYEASTS
However there are some dimorphic fungi ( they switch between these Two forms depending on their environment)
Filamentous (mold-like) FungiFilamentous (mold-like) Fungi Thallus (vegetitive body) –
mass of threads with many branches resembling cotton ball
Mass: mycelium Threads: hyphae, tubular
cells that in some fungi are divided into segments –septate whereas in other fungi the hyphae are uninterrupted by crosswalls-nonseptate
Grow by branching and tip elongation
YEAST like FUNGIYEAST like FUNGI
These fungi exist as populations of single , unconnected , spheroid cells, not unlike many bacteria, although they are sometimes 10 times larger than a typical bacterial cell
Yeasts reproduce by budding
Some fungal species particularly those that cause systemic infection exist as dimorphic fungi
REPRODUCTIONREPRODUCTION
SPORULATIONSPORULATION
The principle way in which fungi reproduce and spread within the environment
Fungal spores are metabolically dormant, protected cells, released by the mycelium in enormous numbers
Borne by the air or water to new sites , where they germinate and establish new colonies
Spores can be generate sexually or asexually
ASEXUAL SPORULATIONASEXUAL SPORULATION
Colour of a particular fungus seen on bread, culture plate is due to theConidia, easly airborne and disseminated
(MITOSIS)
SEXUAL SPORULATIONSEXUAL SPORULATIONmeiosis
Relatively rare compared to asexual sporulation, and spore shape often Used as a method of identification
CUTANEOUS MYCOSESCUTANEOUS MYCOSES-DERMATOPHYTOSES-DERMATOPHYTOSES
EPIDEMIOLOGY Three genera-Trichophyton, Epidermophyton,
Microsporum Anthropophilic-reside on the human skin Zoophilic-reside on the skin of domestic and farm
animals Geophilic-reside in the soil Transmission from humans or animals is by
infected skin scales
PATHOLOGYPATHOLOGY
Dermatophytes use keratin as a source of nutrition
Therefore they infect skin, hair, nailsAll 3 organisms infect /attack skin,
Microsporum does not infect nails and Epidermophyton does not infect hair, they do not invade underlying non-keratinized tissues
CLINICAL SIGNIFICANCECLINICAL SIGNIFICANCE
DERMATOPHYTOSESCharacterized by itching,scaling skin
patches that can become inflamed and weeping
Infection in different sites may be due to different organisms but is given one name
Tinea pedis(Athlete`s foot)Tinea pedis(Athlete`s foot)
Common organisms are Trichophyton rubrum , Trichophyton mentagrophytes and Epidermophyton floccosum.
Initially between the toes spreads to nails, yellow and brittle
Secondary bacterial infection
Id Reaction
Tinea corporis( Ringworm)Tinea corporis( Ringworm)
Epidermophyton floccosum, Trichophyton, Microsporum
Advancing annular rings with scaly center
Periphery of ring area of active fungal growth, usually inflammed and vesiculated
Non-Hairy areas of trunks mostly
Tinea capitis( scalp ringworm)Tinea capitis( scalp ringworm)
Trichophyton and Microsporum species
Depends on area Small scaling patches to
involvement of entire hair with hairloss
Microsporum infects hair shafts , Wood`s lamp
More common in children due to medium chain fatty acids(C8-120 in sebum
TINEA CRURIS/UNGUIUMTINEA CRURIS/UNGUIUM
Epidermophyton , Trichophyton rubrum, simliar to ringworm but thighs and genitalia
Trichophyton rubrum, nails thickened discoloured and brittle , Onchomycosis
Treatment for months until all of the infected nail grows out and is trimmed off
Tinea vesicolorTinea vesicolor
Pityrasis vesicolorDue to Malassezia furfur or Pityosporium
orbiculareTreatment , ketoconazole, fluconazole ,
itraconazole
Diagnosis of Dermatophyte Diagnosis of Dermatophyte InfectionInfection
Nail clippings, skin scrapings, Hair /follicile No role for swabs Placed in sterile container preferably or between 2 slides KOH will be added in the lab to dissolve tissue material Lactophenol blue stain to see if fungal hyphae seen For full identification culture on selective media required
e.g addition of cycloheximide or chloramphenicol, low ph 5.0
May Require 10-14 days for growth Macroscopic and microscopic identification of colonies
Fungal elements/hyphaeFungal elements/hyphae
T.mentagrophytesT.mentagrophytes
T.mentagrophytesT.mentagrophytes
TreatmentTreatment
Samples to be sent for fungal staining and culture Infected skin may be treated with topical
application of antifungal agents miconazole,nystatin and clotrimazole
Refractory lesions oral griseofulvin and itraconazole, terbinafine
Infections of hair and nails usually require systemic ( oral) therapy
SUBCUTANEOUS SUBCUTANEOUS MYCOSES( dermis, subc MYCOSES( dermis, subc
tissues and Bone)tissues and Bone) Causative organisms reside in the soil and in
decaying or live vegetation Almost always acquired through traumatic
lacerations or puncture wounds Common among those who work with soil and
vegetation and have little protective clothing Not usually transmitted humans to humans Usually confined to tropics and subtropics with
exception of Sporotrichosis in USA
SporotrichosisSporotrichosis Sporothrix schenckii-dimorphic fungus Granauloma ulcer at a puncture skin usually a
thorn prick and may produce secondary lesions along draining lymphatics
In most disease is self-limiting may exist in chronic form
Treatment oral itraconazole Chromomycosis : Phialophora or
Cladosporium species
MycetomaMycetoma
Madurella grisea, Actinomadura madura
Localized abscess usually on the feet, that discharge pus serum and blood
Has coloured grains( compact hyphae) black, white, red or yellow depending on organism
SYSTEMIC MYCOSESSYSTEMIC MYCOSES
Blastomyces dermatitidis Coccidioides immitis
Histoplasma capsulatumParacoccidioides brasiliensis
Systemic infective agents
Absidia corymbiferaAspergillus fumigatus
Candida albicansCrytococcus neoformans
Pneumocystis cariniiRhizomucor pusillus
Rhizopus oryzae (R.arrhizus)
Opportunistic fungal Pathogens
Diagram of Systemic mycoses(dimorphic, yeast in infective tissue)
Eastern US
Males
Clinical significanceClinical significance
Simliar to Tuberculosis in that asymptomatic primary infection is seen whereas chronic pulmonary or disseminated infection rare
In the immunocompetent usually mild and self limiting
In the immunocompromised the same infections can be life threatening
CoccidiodomycosisCoccidiodomycosis
Coccidioides immitisMost in arid areas of south-western USIn the soil forms arthrosporesSpores airborne , germinate in the lungs and
produce sphercules filled with many endospores- new spherule
In disseminated cases lesions in the bone or CNS -meningitis
HistoplasmosisHistoplasmosis Histoplasma capsulatum In the soil conidia, germinate
lungs into yeast-like cells Becomes engulfed by
macrophages and XX Benign self-limiting or chronic,
progressive , fatal Disseminated disease only
fungus intracellular RES parasitism
Area Ohio and Mississippi River area
DX: Culture or Exoantigen (immunodiffusion assay)
AIDS patients at particular riskTreatment : Amphotericin or Itraconazole
OPPORTUNISTIC OPPORTUNISTIC PATHOGENSPATHOGENS
Absidia corymbiferaAspergillus fumigatus
Candida albicansCrytococcus neoformans
Pneumocystis cariniiRhizomucor pusillus
Rhizopus oryzae (R.arrhizus)
OPPORTUNISTIC MYCOSESOPPORTUNISTIC MYCOSES
Those that affect the immunocompromised but are rare in normal individual
Organ transplantation, post chemotherapy for cancer, immunodeficient due to Aids and congenital immunodeficiency states
Candida species most commonly occurring fungal pathogen in the ICU setting
CANDIDIASIS(candidiosis)CANDIDIASIS(candidiosis)
Candida albicans and other candida species which are normal flora in the mouth, skin , vagina and intestines
May occur as a results of overgrowth as suppression of bacteria by antibiotics
Manifestations depend on the site e.g. oral candidiasis and vaginal candidiasis and disseminated candidiasis in cancer patients, post GI surgery and AB`s, systemic corticosteroids
Risk Factors for Candida Risk Factors for Candida InfectionInfection
Cellular Immunodeficiency
Antibiotic Use Moisture area Age Hormonal Influence General debility
Interference with Normal flora
Mechanical factors Pregnancy Oral Contraceptives Diabetes mellitus Administration of
corticosteroids
Vulvovaginal candidiasisVulvovaginal candidiasis
Treatment miconazole, clotrimazole topically or oral fluconazoleOr itraconazole
Candida wet preparationCandida wet preparation
Candida species-Gram stainCandida species-Gram stain
Candida culture-24 hoursCandida culture-24 hours
Mucosal CandidiasisMucosal Candidiasis
Pain, redness and sometimes a whitish coating or discharge of the mucosa
Oral candidiasisNappy rash candidiasisVaginal candidiasisEsophageal CandidiasisChronic form
MUCOCUTANEOUS MUCOCUTANEOUS CANDIDIASISCANDIDIASIS
Cellular deficiency results in chronic mucocutaneous candidasis
Oral CandidiasisOral Candidiasis
Occurs in infants without any predisposing factors
Usual predisposing factors Seen in patients taking antibacterials Pain, redness and sometimes a whitish coating
or discharge of the mucosa Candida present in small numbers on the
mucosa and the problem arises when it overgrows
Eosophageal CandidiasisEosophageal Candidiasis
Orophargneal candidiasis may progress to eosophageal candidiasis
Manifestataion of AIDSAlso occurs in those who have predisposing
factors but are HIV-negativeTreatment: fluconazole,itraconazole,
voriconazole or amphotericin
Vaginal CandidiasisVaginal Candidiasis
May occur without any obvious predisposing factors
May occur frequently Treatment: Creams and ointments: Clotrimazole 1% ,
Miconazole 2% Tablets/Pessaries: Clotrimazole, Miconazole,
Terconazole, Nystatin Oral Therapy: Fluconazole, Itraconazole
NAIL CANDIDIASISNAIL CANDIDIASIS
Oral therapy-fluconazole etc
Paronychia
DISSEMINATED DISSEMINATED CANDIDIASISCANDIDIASIS
Treatment amphotericin or fluconazole
Severe candida InfectionsSevere candida Infections
May cause candidaemia, opthalamitis, hepatosplenic candidiasis,
Line infections, secondary peritonitis and urinary tract infections in
Hospitalised patients
As well as mucosal candidiasis
Of Note: candida may contaminate sputum specimens
CRYTOCOCCOSISCRYTOCOCCOSIS
Crytococcus neoformans, found worldwide Especially found in soil containing bird(esp. pigeons)
droppings Characteristic thick capsule that surrounds budding
yeast cell –seen Indian Ink Most common form is mild subclinical lung infection In the immunocompromised often disseminates to the
brain , meningitis often fatal However half those with crytococcal meningitis have
no obvious immune deficiency
CRYTOCOCCUS CRYTOCOCCUS NEOFORMANSNEOFORMANS
In Aids patients it is the second most common fungal infection after candida , potentially the most seriousTreatment: Amphotericin and flucytosine for meningitis and if AIDSSubsequent suppression with fluconazole
ASPERGILLOSISASPERGILLOSIS
Several species of genus Aspergillus, mostly Aspergillus fumigatus
Worldwide distribution, ubiquitous Filamentous molds, produce large numbers of
conidiospores Reside in soil, decomposing organic matter and
dust, associated outbreaks n hospitals with construction work
Disease presentation depends on immunologic status of patient
Disease caused by Disease caused by AspergillusAspergillus
Allergic Bronchopulmonary AspergillosisFarmer`s lungInvasive AspergillosisAspergilloma
Aspergillus fumigatusAspergillus fumigatus
Disease caused by Disease caused by AspergillusAspergillus
Allergic Bronchopulmonary Aspergillosis: in this condition the mould colonises the mucosal surface of lower respiratory tract but does not invade the mucosa. There is intense hypersensitivity response to the Aspergillus antigens> impairment of lung function. Associated abnormal findings on X-ray and asthma like symptoms
Farmer`s LungFarmer`s Lung
Syndrome of shortness of breath typically occuring several hours after exposure to mouldy hay. Antibodies (IgG not IgE) form a precipitate with aspergillus antigen in the alveolar walls and an inflammatory cascade is initiated
Allergic AspergillosisAllergic Aspergillosis
Relatively rare, can arise from inhalation of spores, without subsequent extensive spore germination hyphal invasion
The allergic reaction results in bronchial constriction
Diagnosis by immunoelectrophoresis
ASPERGILLOSISASPERGILLOSIS
Acute Aspergillus infectionsMost severe and often fatal form of
aspergillosis is acute invasive infection of the lungdissemination to brain etc
Less severe form gives rise to a fungus ball( aspergilloma) , a mass of hyphal tissue that forms in lung cavities derived from prior disease
ASPERGILLOMAASPERGILLOMA
Treatment Surgical removal of mass and amphotericinRisk of massive haemoptysis
Diagnosis in the lab by staining and culture: characterisitic V-shaped Hyphae, Septated and spore forming structures
INVASIVE ASPERGILLOSIS INVASIVE ASPERGILLOSIS INFECTIONINFECTION
Treatment Amphotericin( or voriconazole) and supportive therapy NEJMED 2002 Aug 8:347(6);408-15
Often treated empirically, using risk assessment and CT(spiral) to assist in diagnosis
MUCORMYCOSISMUCORMYCOSIS
Most often caused by Rhizopus oryzae and less often by other members of the Mucorales such as Absidia corymbifera, Rhizopus pus
Ubiquitous in nature, spores found in great abunance on rotting fruit and old bread
Usually restricted to those with underlying conditions such as burns, leukaemia or diabetus mellitus
The most common form of the disease can be fatal within a week-Rhino cerebral Mucormycosis
MUCOR MUCOR MYCOSIS/RHIZOPUSMYCOSIS/RHIZOPUS
Rhinocerebral MucormycosisRhinocerebral Mucormycosis
Infection begins in the nasal mucosa or sinuses and progresses to the Orbits, the palate and the brainTreatment: Surgical debridement of necrotic tissue , correction of Underlying disorder and Amphotericin
RHIZOPUS from Skin RHIZOPUS from Skin ScrapingsScrapings
PNEUMOCYSTIS CARINIIPNEUMOCYSTIS CARINIIPNEUMONIA (PCP)Now PNEUMONIA (PCP)Now
known as PNEUMOCYSTIS known as PNEUMOCYSTIS JIROVECI Frenkel 1999JIROVECI Frenkel 1999
Caused by a unicellular eukaryote, Pneumocystis carinii
Before the use of immunosuppressive agents and the onset of the AIDS epidemic , PCP was a rare disease
It is one of the most common opportunisitic diseases of individuals with HIV-1 and usually fatal if untreated
It does not contain ergosterol and is extremely difficult to culture (requires )cultured
PCPPCP
Various cellular forms encysted group of dormant cells and vegetitive form –trophozoite
Ubiquitous Activation of preexisting dormant cells in the
lungs in immunodeficient persons The encysted forms induce an inflammination of
the alveoli-exudate which blocks gas exchange Diagnosis by microscopic examination , by silver
stain or fluorescence of bronchial washings or biopsy
Pneumocystis carinii in AlveoliPneumocystis carinii in Alveoli
Treatment: Combination sulfamethoxazole and trimethoprim, Pentamine and additional agents may also be usedCan be used prophylaxically to prevent infection
Pneumocystis carinii Pneumocystis carinii (jiroveci) pneumonia(jiroveci) pneumonia
LABORATORY LABORATORY IDENTIFICATIONIDENTIFICATION
Standard media –Sabouraud`s agar, potato dextrose agar, low ph 5.0 , inhibits bacterial growth but allows fungal colonies to form
Cultures can be started from spores or hyphae fragments
Specimens: blood, pus, CSF, sputum, tissue biopsies, skin scrapings , nail clippings
Identification by the morphology of conidia structures and carbonhydrate assimiliation tests
LABORATORY DIAGNOSIS LABORATORY DIAGNOSIS OF FUNGAL INFECTIONOF FUNGAL INFECTION
Specimens Depends on site of infection Systemic: -Blood culture( really only useful for
yeast-low sensitivity) or - antigen testing e.g.crytococcal
and histoplamsosis antigen
Pneumonia: Bronchoscopy washings or brushings for staining and fungal culture or bronchial biopsy
LABORATORY DIAGNOSIS LABORATORY DIAGNOSIS OF FUNGAL INFECTIONSOF FUNGAL INFECTIONS
Meningitis: Cerebrospinal fluid for Lactophenol blue staining and indian ink and crytococcal antigen and fungal culture
If Skin infection require skin scrapingsIf nail infection require nail clippings Galactomannan antigen testing for
aspergillus infection
LABORATORY DIAGNOSIS LABORATORY DIAGNOSIS FUNGAL INFECTIONSFUNGAL INFECTIONS
Types of tests carried out Fungal Staining – Lactophenol blue staining or
wet prep using KOH to dissolve tissue material or Calcofluor (fluorescence stain)
Fungal culture on media that encourages fungal growth e.g. PDA
Antigen Testing i.e. to test for antigen present in the wall of fungus e.g crytococcal antigen, galactomannan used in serum and CSF samples
Molecular Methods not used on a routine basis on samples(as yet)
MANAGEMENT OF FUNGAL MANAGEMENT OF FUNGAL INFECTIONSINFECTIONS
Some such as superfical skin infections require topical therapy only with cream e.g.miconazole cream
Some require local therpy e.g. pessaries for vaginal candidasis
Some require oral therapy for skin and nail infections up to 1 year e.g. terbinafine
In the immunocompromised systemic therapy required e.g. fluconazole i./v or amphotericin, voriconazole
MANAGEMENT OF FUNGAL MANAGEMENT OF FUNGAL INFECTIONSINFECTIONS
Important to diagnose fungal infections early in the immunocompromised as there is a high mortality associated with infection
Empirical therapy often started in advance of laboratory diagnosis in these patients
Antifungal Agents: FamiliesAntifungal Agents: Families
Azoles
Allylamines
Benzofurans
Polyenes Macrolides
Pyrimidines
Lipopeptides
Imidazoles Triazoles
Ref: Antifungal Drug Resistance. Clinical Infectious Diseases. 2003:36(Suppl 1) s31-41.
AzolesAzoles
Azoles
Causes Inhibition of C-lansterol 14 α demethylase, (an enzyme required for the synthesis of ergosterol) by binding to cytochrome P450
Resistance may be intrinsic or acquired
Imidazoles Triazoles
Voriconazole
AllyaminesAllyamines
Inhibits squalene epoxidase, an enzyme essential for synthesis of ergosterol
Drug acculmulates in nails, skin and fat
Very useful for nail infections
Polyene MacrolidesPolyene Macrolides
Amphotericin, nystatin Antifungal activity by
binding to membrane sterols such as ergosterol and they increase membrane permeability and leads to cell death
Higher concentrations inhibits Chitin synthase
Active against Aspergillus spp, Candida species ,Crytococccus neoformans , Zygomycetes etc
AmphotericinAmphotericin
Numerous forms Pastilles, Parenteral forms: amphotericin B,
deoxycholate form, colloidal form, Liposomal form
Toxicity: Dose dependent reduction in GFR, by direct vasoconstritive effect on afferent renal arterioles, destruction of renal tubular cells and basement membrane and loss of functioning units
Also nausea .vomiting, phlebitis and ACUTE REACTION: fever,chills,tachyapnea
PyrimidinesPyrimidines
Fluorine analogue of a normal cell constituent cytosine
Demination results in 5-fluorouracil, to 5-flurodeoxyuridylic acid monophosphate, a non-competitive inhibitor of thymidylate synthetase
Used particularly in crytococcal meningitis-74% of serum levels
BenzofuransBenzofurans
GriseofulvinInhibits nucleic acid synthesis, macrotubule
formation and chitin formationActive against ringworm, not candidia or
tinea versicolor
LipopeptidesLipopeptides
Echinocandins, derivatives of pneumocandin BO
Inhibition of 1,3-ß- glucans in the fungal wall, that is glucan synthase inhibitor
Active candida, aspergillosis and pneumocystis carinii in vitro
Licensed for refractory candida( esophageal) infections and invasive Aspergilllosis