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27 Cards in this Set
- Front
- Back
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What is the difference between a yeast and a mould?
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Yeasts - unicellular, reproduce by budding. May form long chains known as pseudohyphae
Moulds - filamentous; grow by extension of hyphae, reproduce by sporulation |
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Most fungi are yeasts or moulds?
Give two examples of each. Are fungi prokaryotes or eukaryotes? |
Most are moulds.
Yeasts - cryptococcus, candida Moulds - mucor, aspergillus Eukaryotes. |
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What does diamorphic mean?
Name 4 important diamorphic fungi. |
Yeast form at body temp. Mould form at room temp.
Histoplasma, coccidiodes, paracoccidiodes, sporothrix, blastomyces |
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Which two species can be transmitted human-to-human?
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Candida and dermatophytes (microsporum, trichophyton, epidermiphyton)
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What are the three basic classifcations of fungal infection?
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Superficial, subcutaneous, systemic (deep) mycoses.
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Example of superficial mycosis?
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Ringworm (tinea): dermatophytes. Can be caused by any of microsporum, trichophyton, epidermiphyton. Affects keratinized tissue.
Tinea corporis (body), crura (groin), unguum (fingers), capitis (head), pedis (feet) |
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Example of subcutaneous mycosis?
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Sporotrichosis: introduced from soil or vegetation - gardeners or forest workers. Ascending lymphangiitis.
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What does microsporum cause?
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Tinea capitis - fluoresces green under a Wood lamp (black light - UVA)
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What is the major risk factor for systemic mycoses?
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Immune compromise
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Which systemic mycoses are invasive (can cause disease in healthy host)? Which are opportunistic?
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Invasive: histoplasma, coccidiodomycosis, paracocc., blastomyces
Opportunistic: candida, cryptococcus, mucor/rhizopus, aspergillus |
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Name the 2 polyene antifungals. How do they work?
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Nystatin and amphotericin.
They bind ergosterol in the cell membrane, causing permeability, electrolyte leakage and death. |
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What are the major toxicities of amphotericin?
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Nephrotoxicity, anaphylaxis, anemia, fever/chills, hypotension, arrhythmia, iv phlebitis
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Terbinafine: How does it work? What is it used for? Name one side effect.
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Oral or topical antifungal. Inhibits ergosterol synth by inhibiting squalene epoxide formation (the precursor for lanosterol).
Useful in tinea infection. Very useful as accumulates in keratin and continues to work after stopping treatment. Hepatotoxicity - avoid in liver disease. |
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Griseofulvin: How does it work? What is it used for? Name three side effects.
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Oral antifungal.
Interferes with microtubule formation and mitotic spindle? Only used in dermatophyte infections of skin, hair or nails. Photosensitivity (CI in porphyria), leukopenia, urticaria. Interferes with warfarin. |
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Flucytosine (5FC): How does it work? What is it used for?
Two side effects? |
Oral or IV.
Converted intracellularly into 5-FU, which interferes with fungal RNA. Yeasts only (crytococcus, candida). Marrow toxicity and hepatotoxicity. important - often used with amphotericin for treatment of cryptococcal meningitis (two week course) |
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Name the azole antifungals
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Two groups:
Imidazoles: Clotrimazole, ketoconazole, etc. Triazoles: Fluconzaole, itraconazole, voriconazole, posiconazole |
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What are the imidazoles used for?
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Superficial infection eg vaginal candidiasis
Ketoconazole ass'd with fatal hepatotoxicity and not used much. |
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What is fluconazole mainly active against?
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Candida albicans.
NB - not active against aspergillus |
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What is voriconazole particularly good for?
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Aspergillus including amphotericin resistant Asp. terreus and non-albicans candida.
NB - not active against mucor/rhizopus |
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What use is posiconazole?
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Similar to voriconazole. Also has activity against mucor. Reserve for amphotericin failure.
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Name the echinocandins, their principle activity and MOA.
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Caspofungin, micafungin, anidulafungin. Mainly used for candida and aspergillus.
Inhibit beta-glucan synthase in cell wall - fungistatic only. |
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Name the 5 classes of antifungals and an example of each.
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polyenes - nystatin, amphotericin
azoles - clotrimazole, voriconazole echinocandins - caspofungin allylamines - terbinafine, griseofulvin nucleosides - 5FC |
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What is the treatment of choice for histoplasmosis?
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Itraconazole
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What is the best treatment for opportunistic mycoses (eg aspergillosis)?
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Amphotericin
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Besides amphotericin what can be used to treat aspergillosis?
What should not be used? |
Voriconazole or casporfungin.
Fluconazole should not be used. |
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What is standard treatment for PCP pneumonia?
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Trimethoprim-sulfamethoxazole - use high dose IV admin if severe.
Also used for PCP prophylaxis |
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What agent would be a useful candida prophylaxis? When would it be used?
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Oral fluconazole. Use when low CD4 count or high viral load.
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