Download Mycology 2 DPT-6

Mycology 2
Systemic & Oppurtunistic
Fungi
DPT-6
Dr Sadia Ikram
Systemic Mycoses
Transmission
• Result from inhalation of spores of
dimorphic fungi having mold forms in soil.
• In lungs, spores differentiate into yeasts.
• Most lung infections asymptomatic.
• Disseminated disease in some people
destructive lesions & death.
• not communicable to others.
Systemic Mycosis
• Coccidioides immitis causes coccidioidomycosis.
• Histoplasma capsulatum causes histoplasmosis.
• Blastomyces dermatitidis causes blastomycosis or
North American blastomycosis.
• Paracoccidioides brasiliensis causes
paracoccidioidomycosis or South American
blastomycosis.
Pathogenesis & Clinical Findings
• These organisms spread within a person by
direct extension or via bloodstream.
• Granulomatous lesions occur in any organ,
primarily in bones & central nervous system
(meningitis).
Laboratory Diagnosis
• Microscopy.
• Cultures on Sabouraud's agar.
• Serologic tests: IgM and IgG appear within 2
to 4 weeks of infection.
Treatment
• Amphotericin B (Fungizone) or itraconazole.
• Ketoconazole effective in lung disease.
• No means of prevention.
Oppurtunistic Fungi
• No disease in immunocompetent persons.
• Cause diseases in immuno-compromised
host.
• Candida albicans.
• Cryptococcus neoformans.
Candida albicans
• Causes thrush, vaginitis, esophagitis, diaper
rash, and chronic mucocutaneous candidiasis.
• Disseminated infections like right-sided
endocarditis (in intravenous drug users).
• Blood stream infections (candidemia), and
endophthalmitis.
• Infections related to indwelling intravenous
and urinary catheters.
• Can. albicans oval yeast with a single bud.
• Part of normal flora of mucous membranes of
upper respiratory, gastrointestinal, and female
genital tracts.
• In tissues it appear as yeasts or pseudohyphae.
Transmission
• The presence of Can. albicans on the skin
predisposes to infections involving instruments
that penetrate the skin, such as needles and
indwelling catheters.
• Infections in immunocompromised people.
Pathogenesis & Clinical Findings
• Overgrowth of Can. albicans in mouth
produces white patches (thrush or
pseudomembrane.
• Vaginitis with itching and discharge favored by
high pH, diabetes, or use of antibiotics.
• Skin invasion in warm, moist areas, which
become red and weeping.
• Fingers and nails involved onrepeated
immersion in water.
• Thickening or loss of the nail can occur.
• Diaper rash in infants: when wet diapers not
changed promptly.
• In immunosuppressed individuals, Intravenous
drug abuse, indwelling intravenous catheters:
Candida disseminate to many organs or cause
chronic mucocutaneous candidiasis, rightsided endocarditis and endophthalmitis.
Laboratory Diagnosis
• Microscopy: In exudates or tissues, budding
yeasts and pseudohyphae appear gram-positive.
• Can be visualized by calcofluor-white staining.
• In culture: yeast colonies are formed resembling
large Staphylococcal colonies.
• Germ tubes form in serum at 37°C, serves to
distinguish Can. albicans from other Candida
species.
• Serologic testing.
Treatment
• For oropharyngeal or esophageal thrush:
Fluconazole, Caspofungin or micafungin.
• Skin infections: topical antifungal drugs, e.g.,
Clotrimazole or nystatin.
• Mucocutaneous candidiasis: Ketoconazole.
• Disseminated candidiasis: Amphotericin B or
fluconazole.
• Candidal infections, e.g., thrush, prevented by
oral clotrimazole, nystatin or Micafungin.
• No vaccine.
Cryptococcus
• Cryptococcus neoformans causes
cryptococcosis (cryptococcal meningitis).
• Cryptococcosis most common life-threatening
fungal disease in AIDS patients.
Properties & Transmission
• Oval, budding yeast surrounded by a wide
polysaccharide capsule.
• Not dimorphic.
• Occurs widely in nature and grows abundantly in
soil containing bird (especially pigeon)
droppings.
• Birds not infected.
• Human infection results from inhalation of
organism.
• No human-to-human transmission.
Pathogenesis
• Lung infection often asymptomatic.
• May produce pneumonia.
• Disseminates to central nervous system
(meningitis) and other organs.
• Subcutaneous nodules.
Laboratory Diagnosis
• Microscopically: In spinal fluid mixed with India
ink, the yeast cell seen surrounded by a wide,
unstained capsule.
• Methenamine silver, periodic acid–Schiff, and
mucicarmine staining technique.
• Cultured from spinal fluid and other specimens:
colonies highly mucoid.
• Serologic tests: capsular antigen in high titer in
spinal fluid, detected by latex particle
agglutination test.
Treatment
• Amphotericin B and flucytosine used in
meningitis and disseminated disease.
• Fluconazole used in AIDS patients for longterm suppression of cryptococcal meningitis.
• No prevention.