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34 Cards in this Set
- Front
- Back
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Endogenous causes of OIs |
Cancer Leukemia |
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Exogenous causes of OIs |
Immuno suppressive therapy AIDS |
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Examples of Opportunistic Mycoses (fungal infections) |
Candidiasis Cryptococcosis Aspergillosis Zygomycosis/Mucormycosis Pneumocystosis Penicilliosis |
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Candida spp - normally habitat |
Body surfaces - skin + mucous membranes |
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Candida - epidemiology |
Most common invasive fungal infection in Immuno compromised 4th most common cause of nosocomial π©Έ stream infection |
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Candida - species implicated in human disease |
C albicans C tropicalis - graceful long pseudohyphae C parapsilosis - short curved pseudohyphae C krusei - tree-like elongate blastoconidia C lusitaniae - slender branched curved PH C glabrata - no pseudohyphae |
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C albicans - habituated |
GIT upper Respiratory tract Buccal cavity Vaginal tract (Growth normally suppressed by other microbes) |
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Candida - structure |
Thick cell wall - mannan + glucan PS Unicellular Asexual reproduction - budding Filament formation - pseudohyphae (buds attached w chains of blastospores) or hyphae (buds germinate) |
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Candida - virulence factors |
Switching of phenotype Hyphae formation - tissue invasion Hydrophobicity- more virulent at same π‘ Virulence molecules - C3d, iC3b, fibrinogen, laminin, fibronectin, fucose receptors, N-acetylglucosamine receptors Molecular mimicry - surface coat mimics host -> dec recognizability eg C albicans get coated w host platelets via fibronectin Lytic enzymes - aspartyl proteinase (most potent) + hydrolases Growth rate - virulent strains have shorter doubling β° than attenuated |
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Candida - risk factors (11) |
Neutropenia DM AIDS myeloperoxidase defects Broad-spectrum antibiotics Indwelling catheters Major surgery Organ transplant Neonates Severity of any illness IV drug addicts |
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Candidiasis- clinical forms |
Mucosal candidiasis- 1. thrush (oropharyngeal), 2. Esophagitis + 3. Vaginitis Cutaneous candidiasis- 1. Paronychia (skin around nail bed), 2. Onychomycosis (nails), 3. Diaper rash, 4. Balanitis + 5. chronic mucocutaneous candidiasis (kids w T cell abnormality) |
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Candida - main defense mechanisms |
In presence of normal flora - skin + mucus membranes Phagocytosis by polymorphonuclear cells > Macs + CD4+ |
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Candida - specimens for lab dx |
Blood Tissue Sterile fluid Urine CSF Skin Respiration secretions |
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Candida - 1o (inherent) antifungal resistance |
C lusitaniae - amphotericin B C glabrata + C krusei - fluconazole |
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Candida - 2o (acquired) antifungal resistance |
Fluconazole, other azoles Amphotericin B 5-FC |
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Candida - rx |
Remove infected iv lines Systemic infection - antifungal IV amphotericin B Azoles - fluconazole, itraconazole, voriconazole, posaconazole Echinocandins - caspifungin, micafungin Flucytosine WITH Amphotericin B |
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Candida - lab dx tests |
PCR Culture - eg sabouroudβs dextrose blood π©Έ agar Microscopy - gram stain, calcofluor Histopath- tissues |
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Candida albicans - oxgall agar |
Large round + thick walled Chlamydospores (terminal vesicle) |
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Candida albicans - cornmeal agar |
Clusters of blastospores along pseudohyphae @ regular intervals |
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What is germ tube, and positive and negative? |
Germ tube - inoculation of yeast in π serum Positive - C albicans, C dubliniensis (continuous filament germinating from yeast cell w/o constriction @ attachment pt) Negative - other Candida spp esp C tropicalis (constriction@ attachment pt) |
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Candida albicans - sabouraud dextrose blood agar |
Creamy white smooth yeast cells; pseudohyphae + hyphae seen |
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Candida albicans - chromagar |
Green colonies |
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Yeast ID ie how C albicans is differentiated from other candida spp |
Budding of yeast cell Germ tube test Chlamydospore formation @ 22oC on cornmeal agar |
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Cryptococcosis - etiological agent + epidemiology |
Cryptococcus neoformans (Encapsulated yeast) Occurs in sporadic form & is an OI 2nd most common fungal infection in HIV (CD4+ < 200cells/mm3) Isolated from pigeon nests, droppings, old buildings + nitrogenous soil (creatine) Extra π« cryptococcosis is an AIDS-defining disease |
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Cryptococcosis - virulence factors |
Capsule (π phagocytosis) Melanin production by phenol oxidase β> antioxidant β> π intracellular killing |
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Cryptococcosis - pathogenesis |
Infection via inhalation, skin or mucosa Weak IS β> reactivation + dissemination to CNS + other sites Visceral form stimulates TB + cancer Cutaneous form varies from ulcers to granulomas |
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Cryptococcosis- specimen for lab dx |
Serum CSF Body fluids |
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Cryptococcosis- lab dx tests |
Direct exam - (1) wet mount w India ink - budding yeast cells w halo; (2) gram +ve budding yeast cells Fungal culture - (1) SDA - mucoid, cream to buff colored; (2) Birdseed (Niger seed) agar - ubrown (due to melanin) Serology - (1) Crypto LA test - anti capsular Abs used to detect capsular Ag; (2) Abs can be detected in serum |
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Cryptococcosis- rx |
Antifungals - Amphotericin B (AMB), Flucytosine |
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Cryptococcosis- clinical types |
Pulmonary (1o infection) Extra pul - cryptococcal meningitis is most serious, resembles TB and often in AIDS |
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Cryptococcosis- clinical types |
Pulmonary (1o infection) Extra pul - cryptococcal meningitis is most serious, resembles TB and often in AIDS |
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Cryptococcosis- prophylaxis |
Conjugate vax |
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Clinical features of Pulmonary Cryptococcosis |
Asymptomatic May have chronicπ« disease too Subclinical - only discovered by routine CXR π€ + cough + chronic granuloma β> invasive PC β> inc risk of spread to CNS |
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Clinical features of Extra Pulmonary Cryptococcosis in CNS |
Meningitis Meningoencephalitis Expanding cryptococcoma (localized solid tumor-like masses) |
