Mycology Flashcards by Trenni Jefferson

What do anti-fungal drugs target?

Ergosterol synthesis pathway and beta (1,3) glucan synthase

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Fungal cell characteristics

Eukaryotes
Cell wall has glucan and chitin
Cell membrane contains sterols with phospholipid bilayer

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___________ is the study of fungi

Mycology

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Who is susceptible to mycoses

Critically ill and immunosuppressed patients with central vasc. catheters

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Characteristics of fungi of clinical importance

Hyphae or pseudohyphae (septate, aseptate/ coenocytic, smooth, rough, branched)
Yeast (budding)
Conidia (macro or micro)

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What does fungi grow as in the lab?

Mold or yeast on Sabouraud’s Dextrose Agar (SDA)

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Dermal, SubQ species of pathogenic fungi

Microsporum species (M. canis)
Trichophyton (T. verrucosum)
Malassezia pachydermatis
Sporothrix schenkii (SQ)

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Systemic species of pathogenic fungi

Histoplasma capsulatum
Blastomyces dermatitidis
Coccidiodes immitis
Cryptococcus neoformans (mold, monomorphic, opportunistic)

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Opportunistic species of pathogenic fungi

Aspergillus fumigatus (mold, monomorphic, opportunistic)
Candida albicans and C. auris

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Zygomycetes

Mucor, absidia, mortierella, rhizopus species
Multiple forms, opportunistic, specific situations, not common

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________ is not a true fungus, but a fungus-like

Pythium insidiosum

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Dermatomycoses

Ringworm
Trichophyton (verrucosum- cattle, rubrum- human, mentagrophytes- horse)
Microsporum (canis and equinum)

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Non-dermatophytes

Malassezia pachydermatis and M. nana

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Dermatophytes lab growth conditions

Dermatophyte test medium (DTM)
SDA agar
T. verrucosum @ 37C

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Dermatophytes dx

Wood’s lamp (M. canis)- fluorescence
Hair/ skin microscopy
Culutre and ID (conidia)
KOH mount (ectotrix formation, arthropsores)

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Malassezia and otitis/ dermatitis characteristics

Oval to cylindrical yeast
Normal flora in ear canal
Opportunistic and peanut shaped

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Malassezia host related factors

Excess wax, high humidity, hairy, pendulous ears, dermatitis, etc.

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The CS show by Malassezia is …

Lichenified skin (elephant skin)

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Sporotrichiosis

“Rose-gardener disease”
Cause by S. schekii (dimorphic, SQ invasive mycosis)
North and South America

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S. schenkii colony growth

Small white with no cottony aerial hyphae → becomes moist, wrinkled, leathery and darkens to brown or black

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S. schenkii in culture/ extracellular

Septate, thin, branching hyphae, slender tapering conidiophores (mold)
Conidia: pear shaped rosette cluster

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S. schenkii in tissue

Round oval fusiform budding (cigar bodies) - yeast

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Histoplasma, Blastomyces, Coccidiodes characteristics

Thermally dimorphic
Inhalation
Many organ systems: mucocutaenous ulcers draining tracts + interal organs

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Histoplasma

H. capsulatum capsulatum in N. America
Only intracellular localization fungus in host macros

Histoplasmosis distribution

Ohion and Mississippi river valleys (TN, MS, OH, MO, St. Lawrence river basins)

Histoplasmosis transmission

Humid environments with nitrogenous soils contaminated with bird or bat droppings (chicken coops, shed feathers, starling roosts)

Blastomycosis

B. dermatitidis Yeast form: broad based budding Lungs and associated LNs

Blastomycoses distribution

Upper mid-western and souther US along St. Lawrence river

Blastomycosis CS

No asymptomatic colonization Hematogenous to skin, bones, UT, CNS Cornea, retinal detachment and glaucomatous

Untreated blastomycosis is __________

FATAL (80%)

Coccidioides

Valley fever, CA fever, San Joaquin Valley fever, desert rheaumatism causes by C. immitis

C. immitis growth

25C and37C filamentous 38-40C spherule/ tissue form Athrospores formed in 1-2 weeks

Coccidioides CS

In tissue or body fluids: large, round, thick walled spherules with endospores

Coccidiodomycosis (Valley Fever)

Desert/ semi arid areas of SW US and northern Mexico, Central and S. America

Lab Dx for Histoplasma, Blastomyces, Coccidiodes

Direct exam Latex agglutination test Immunofluorescence Serology (Agar gel immunodiffusion)

What other fungal organisms can be found with AGID

Aspergillus, candida, paracoccidioides, farmers lung (hypersensitivity pneumonitis)

Crytococcal Ag lateral flow assay

Immunochromatographic test system for detection of capsular polysacc, Ags in serum and CSF

Cryptococcosis

Encapsulated yeast C. neofromans Found in soil, esp. with pigeon guano Inhalation from environment

Cryptococcosis CS

Self-limiting lung infection Pulmonary: pneumonia, dry cough, dyspnoea Entrapulmonary: meningitis, skin lesions

Aspergillus growth

Colonies are white → yellow, green, brown, black Velvety or cottony texture

Aspergillus physical characteristics

Septate hyphae, unbranched conidiophore (foot cells), vescicles Chains of round conidia

Aspergillosis

Ubiquitous molds grown in decating debris (A. fumingatus) Inhalation

Aspergillosis pathogensis

Spores colonize airway (asymptomatic) → local inflammatory response → lethal invasive infection

Candida

Yeast, opportunistic Normal inhabitant of the the upper GI tract and moist skin folds

Candidiasis importance

Most common blood isolate Grows in body yeast as pseudophyphae C. albicans most common

Candida auris

Drug-resistant, spreads in healthcare facilities (anti-fungals don't work!!)

Pythiosis (Swamp cancer)

FL horse leeches, Canckers, Ferida da Moda... Caused by Phythium insidiosum GIT and cutaneous forms

Pythiosis distribution

Wetland regions: gulf coast and south eastern states

Pythiosis CS

Motile endospores that affect lower extremities (skin) and ingested with contaminated water Granulomatous ulcerative disease

___________ is causes by Pseudogymnoaocus destructans

White-nose syndrome *worst wildlife diseases, killed millions of bats*

Zygomycosis

Commonly abundant saprophytic zygomycetes Mortierella, Absidia, mucor and Rhizopus Aseptate, hyphae, grow rapidly

Zygomycosis in domestic animals

Gastritis and abortion in bovines Mycotic abortion and placentitis (ruminants) Guttural pouch and cervico-uterine infection (horses) Cutaneous disease, mastitis, pneumonia

Zygomycosis dissemination

Fatal because of angio-invasion and thrombosis

Zygomycosis in humans

Diabetes is a high-risk predisposing factor

Polyene drugs

Amphotericin B, nyastatin Ergosterol is the target

Imidiazole drugs

-azole group Ketaoconazole, fluconazole, itraconazole Ergosterol synthesis is the target

5-fluorocytocine

DNA synthesis inhibitor

Griseofulvin

Binds tubulin Interference with fungal cells mitosis and concdentrated in the epithelium Teratogenic

Terbinafine

Ergosterfol synthesis inhibitor