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Mycology
| Question | Answer |
|---|---|
| Characteristics of Fungi- Reproduction | • Sexual- fusion of 2 haploid nuclei; spores- teleomorph • Asexual- mitotic division of haploid nucleus and budding production of conidia- anamorph |
| Characteristics of Fungi- Growth and morphology: Hyphae | • Tube-like structures with thick parallel walls • Septate-has cross walls • Aseptate (coenocytic)rare cross walls • Mycelium is a matt of hyphae • Vegetative growth into medium • Aerial growth above the medium |
| Characteristics of Fungi- Growth and morphology: Pseudohyphae | • Are elongated budding yeast cells (blastoconidia) with constrictions between cells (buds) |
| Characteristics of Fungi- Growth and morphology: Fruiting bodies part 1 | • Sexual (perfect, teleomorphic) Ture sporulation Fusion of haploid nuclei Homosexual- sygospore Heterosexual- oospore Spore sacs (asci) Cleistothecium (round, closed) Perithecium (flask-shaped, open) Apothecium (saucer-shaped, open) |
| Characteristics of Fungi- Growth and morphology: Fruiting bodies part 2 | • Asexual (imperfect, anamorphic) Specialized supportive hyphae Chlamydoconidia- round, thick-walled structures located terminal, intercalary, sessile Arthroconidia- hyphal fragmentation at cross walls Aerial structures Conidiophore, vesicle, |
| Classification part 1 | • Zygomycetes- ribbon-like aseptate hyphae; sexual and asexual • Ascomycetes- septate; sexual and asexual; produce asci |
| Classification part 2 | • Basidiomycetes- septate; sexual; mushroom; club fungi • Deuteromycetes (Fungi Imperfecti)- no sexual stage; many common pathogens |
| Lab Methods part 1 | • 10% KOH wet prep- clears debris and breaks down keratin from nails and hair • Lactophenol cotton blue Stains and kills organism Use with culture material • India ink- capsule of Cryptococcus neoformans |
| Lab Methods part 2 | • Primary growth agars Sabouraud’s Dextrose agar (SAB) – glucose, peptone, pH 5.6 Mycosel – mimilar to SAB but contains cycloheximide, BHI with 5% SRBC’s, gentamicin, and chloramphenicol Cycloheximide used in yeast differentiation |
| Lab Methods part 3 | • Specialty growth media Bird-seed agar- Cryptococcus neoformans (brown colonies) Corn meal agar- Candia albicans (Chlamydoconidia) |
| Specimen Collection and Handling | • Optimum temp = 25-30°C • Hold 6 weeks • Use screw-cap tubes or tape plates to avoid accidental opening and drying • Work under a biologic safety hood |
| Dermatophytes part 1 | • Use keratin as nitrogen source • Tinea- ringworm • Septate hyphae; micro- and macroconidia • Cause tinea capitis |
| Dermatophytes part 2 | • KOH prep of scales from advancing margin of lesion, hair, or nails • Wood’s lamp- some dermatophytes fluoresce with UV light (Microsporum in hair) • Treatment- miconazole, clotrimazole, griseofulvin |
| Dermatophytes cause tinea capitis | • Endothrix (inside shaft) – temporary hair loss • Ectothrix (outside shaft) – permanent hair loss |
| Microsporum | • Affects hair and skin • Mostly in children • Macronidia- large, spindle shaped, rough with 4-15 septa • Microconidia- small, club shaped |
| Microsporum audouinii | • Epidemic tinea capitis • Hyphae usually sterile • Terminal chlamydoconidia • 10-21 days for growth • Reddish-brown color on reverse side of colony • Hairs fluoresce yellow-green |
| Microsporum canis | • Causes dog and cat ringworm which is passed to humans • Macronidia- abundant with 4-8 septa, knoblike, echinulate (rough) ends • Thick walls • Growth 4-5 days • Yellow color on reverse side of colony • Ectothrix |
| Microsporum gypseum | • Many macronidia with 3-5 septa and echinulate surface (rounded ends, not knobby) • Thin walls • Orange-brown color on reverse side of colony • Ectothrix |
| Trichophyton | • Affects skin, hair, and nails • Primarily in adults • No fluorescing hairs • Few or no macronidia- think, smooth walls • Many microconidia |
| Trichophyton mentagrophytes | • Microconidia- numerous, spiral, and nodular bodies; white, cottony mycelium • Rose-brown color on reverse side of colony • Endothrix • Urease positive in 2-3 days |
| Trichophyton rubrum | • Microconidia- tear shaped and dispersed along hyphae • Cherry red color on reverse side of colony • Urease negative • Ectothrix |
| Trichophyton tonsurans | • Black dot ringworm (hair breaks off) • Endothrix • Yellow-red on reverse side of colony • Microconidia, clavate (club shaped) varying in size (balloon forms and “matchstick”) • Chlamydoconidia in older cultures • Spores not commonly, only hyphae |
| Trichophyton schoenleinii | • Causes favus (severe tinea capitis) • Endothrix • Slow growth, waxy colonies, favic chandeliers (look like “deer antlers”) and chlamydoconidia |
| Trichophyton violaceum | • Affects scalp and body • Wrinkled, yeast-like purple colony • Hyphae and chlamydoconidia in chains |
| Epidermophyton floccosum | • Skin and nails (especially feet, hands, and groin) • Macroconidia Large, smooth, club-shaped Found in singles or clusters at end of hyphae 2-4 septa • No microconidia • Olive green or khaki color |
| Yeast- Cryptococcus neoformans part 1 | • Yeast; no Pseudohyphae; brown colonies on bird seed agar • Mucoid colonies- capsule (detected with India ink) • Urease positive • Inhibited by cycloheximide |
| Yeast- Cryptococcus neoformans part 2 | • Found in pigeon and bird droppings • Meningitis (found in spinal fluid) and septicemia in immunocompromised host • Amphotericin B or flucytosine for treatment |
| Yeast- Candia albicans | • Yeast, Pseudohyphae • Germ tube positive • Chlamydoconidia on cornmeal agar (CMAT) • Human flora |
| Dimorphic fungi | • Yeast or tissue phase at 36°C; mold phase at 30°C • Treatment- Amphotericin B |
| Histoplasma capsulatum | • Small yeast forms in tissue • Mycelia form exhibits tuberculate macroconidia- diagnostic • Infects RES- bone marrow specimen of choice • Primary focus pulmonary • May be confused with Sepedonium |
| Blastomyces dermatitidis | • Large yeast cells with broad based buds and double contoured wall; mold phase produces ‘lollipop’ forms • Primary focus pulmonary; skin lesions common • Confused with Scedosporium apiospermum (do conversion studies) |
| Coccidioides immitis | • Tissue form- large, round walled spherule containing endospores (vary in size) • Mold phase-thick walled, alternate staining Arthroconidia (very infectious to lab person) • Endemic in desert southwest &semiarid regions • Primary focus pulmonary |
| Paracoccidioides brasiliensis (South American blastomycosis) | • Yeast form diagnostic- multiple blastoconidia budding from sides of large blastospore (“Mariner’s Wheel”) • Primary focus pulmonary; can simulate TB • May have cutaneous or mucocutaneous lesions |
| Subcutaneous Fungi: Sporothrix schenckii (Dimorphic) part 1 | • Found in soil, plants, decaying matter • Traumatic inoculation through skin (gardeners, farmers via rose thorns); usually on hand |
| Subcutaneous Fungi: Sporothrix schenckii (Dimorphic) part 2 | • Pyogenic and granulomatous inflammatory reaction • Yeast phasr- ovoid, “cigar” bodies • Mycelial phase- delicate branching hyphae with ovoid conidia clustered at tip in “rosette” head or alongside like a “sleeve” |
| Chromoblastomycosis | • Phialophora and Cladosporium- foot or leg • Scaly, wart-like lesions • Brown pigmented hyphae |
| Chromoblastomycosis characteristics part 1 | • Cladosporium (C. carionii) – canidia in branched chains • Phialophora (P. verrucosa) – conidia produced in flask-like conidiophore or phialide |
| Chromoblastomycosis characteristics part 2 | • Acrotheca (Rhinocladiella-like) (Fonsecaea pedrosoi) – conidia formed alongside of irregular, club shaped conidiophores; this genus exhibits all 3 types of sporulation |
| Mycetoma part 1 | • Found in the tropics • Foot trauma; draining sinuses • Purplish discoloration and tumor-like deformities that drain pus with granules • Actinomycotic- Nocardia, Actinomadura • Fungal |
| Mycetoma part 2 | • White cottony mycelium; turns brown with age; oval conidia borne on conidiophores (“lollipop”) • May also be found in eye, sinuses, brain abscess • Opportunist in compromised patients |
| Microscopic observations: small extracellular yeast | • Candida sp • Sporothrix schenckii |
| Microscopic observations: small intracellular yeast | • Histoplasma capsulatum |
| Microscopic observations: yeast with capsule | • Cryptococcus neoformans |
| Microscopic observations: yeast with pseudohyphae | • Candid sp |
| Microscopic observations: large yeast with broad-based buds | • Blastomyces dermatiditis |
| Microscopic observations: large yeast with multiple buds | • Paracoccidioides brasiliensis |
| Microscopic observations: endospherules and endospores | • Coccidiodes immilis |
Created by:
evk2369
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