Mycology & Virology Practice Flashcards

A set of practice flashcards covering key mycology and virology concepts, including fungal biology, diagnostic methods, dermatophyte morphology, systemic mycoses, and foundational virology topics.

What are the defining cellular and growth characteristics of fungi?

Eukaryotic, achlorophyllous organisms that obtain nourishment from the environment; generally obligate aerobes; cell walls contain chitin, glucans, and mannans; membranes contain ergosterol; require moisture for growth.

What are the two main fungal forms and their typical growth temperatures?

Yeast (unicellular; reproduces by budding/fission; grows at 37°C) and Molds (multicellular; grows at 20–25°C).

What do the terms monomorphic, dimorphic, and polymorphic mean in fungi?

Monomorphic: exists as yeast or mold only; Dimorphic: exists as yeast or mold; Polymorphic: can have both forms in the same culture (e.g., Exophiala).

What is the fundamental unit of fungi and what is the mass composed of called?

Hyphae; a mass of hyphae is called mycelium.

What is the difference between aseptate (coenocytic) and septated hyphae, and which group commonly lacks septa?

Aseptate hyphae lack cross walls; Septated hyphae have cross walls; Zygomycetes (Mucorales) commonly have aseptate hyphae.

What are the two pigmentation categories of fungi and give examples?

Hyaline/moniliaceous (lightly pigmented; e.g., Aspergillus, Fusarium, Rhizopus) and Dematiaceous/Phaeoid (darkly pigmented; e.g., Alternaria, Bipolaris, Cladosporium, Phialophora).

Name the major sexual and asexual spore types in fungi.

Sexual spores: asci (ascospores), basidia (basidiospores), zygospores, oospores. Asexual spores: arthroconidia, conidia (macroconidia, microconidia), blastoconidia, chlamydospores.

What is a 'perfect' fungus?

A fungus that can undergo both sexual and asexual reproduction.

What is an 'imperfect' fungus?

A fungus that undergoes only one mode of reproduction (sexual or asexual).

Name the fungal phyla and representative genera as mentioned.

Zygomycota: Mucor, Absidia, Rhizopus; Ascomycota: Aspergillus, Saccharomyces, Histoplasma capsulatum; Basidiomycota: Cryptococcus neoformans; Deuteromycota (Fungi Imperfecti): Dermatophytes and Fusarium.

Which stains are used for routine fungal microscopy and what is each used for?

KOH mounts (detect fungal elements in skin/hair/nails); Lactophenol Cotton Blue (permanent mounts); India ink (capsule of Cryptococcus neoformans); Calcofluor white (fluorescent staining for chitin); PAS and Gomori’s methenamine silver (tissues); Giemsa/Wright (historic fungal staining); Fontana Masson & H&E (special purposes); Acridine Orange (fluorescence).

What is the purpose of Wood’s lamp in fungal diagnosis?

To detect fluorescence of certain dermatophytes; Microsporum canis shows yellow-green fluorescence; Microsporum audouinii shows apple-green fluorescence.

What is the standard culture medium for routine fungal cultivation?

Sabouraud Dextrose Agar (SDA).

What media is used specifically for dermatophytes that contains chloramphenicol and cycloheximide?

SDA with antibiotics, also called Mycobiotic/Mycosel.

Which medium stimulates sporulation of Candida albicans in culture?

Corn Meal Agar (CMA).

What medium is used to detect Cryptococcus neoformans pigment production?

Niger Seed (Bird Seed) medium.

Which medium is used to assess pigment production for dermatophytes like Trichophyton rubrum?

Potato Dextrose Agar.

Which medium is used to detect pigment production of Malassezia furfur?

Malt Extract Agar.

What is the significance of 'Rice Medium' in dermatophyte testing?

Positive for Microsporum canis; negative for Microsporum audouinii.

Describe the Microsporum canis and Microsporum audouinii macroconidia.

M. canis: spindle-shaped, large, multiseptate with knobby projections; M. audouinii: bizarre-shaped macroconidia.

What fluorescence pattern is associated with Microsporum canis on Wood’s lamp?

Yellow-green fluorescence.

What fluorescence pattern is associated with Microsporum audouinii on Wood’s lamp?

Apple-green fluorescence.

How do you differentiate Microsporum canis from Microsporum audouinii using Rice Medium?

M. canis: Rice Medium positive; M. audouinii: Rice Medium negative.

What are hair infection patterns for Trichophyton tonsurans and Trichophyton rubrum in terms of microconidia shapes?

T. tonsurans: microconidia globose in grape-like clusters; T. rubrum: tear-shaped or clavate microconidia laterally on hyphae.

Which dermatophyte shows antler hyphae (Favic chandelier) morphology?

Trichophyton schoenleinii.

What is the hair invasion pattern for Microsporum canis?

Not specified here; the note highlights “Birds on a fence” appearance for M. canis in one mnemonic; key distinguishing features include cat/dog reservoir and fluorescence, not a fixed hyphal pattern.

Which organism causes Sporotrichosis and what is the yeast form at 37°C?

Sporothrix schenckii; cigar-shaped yeast.

What is a hallmark of Chromoblastomycosis on histology?

Sclerotic (muriform) bodies, medlar bodies, copper penny–like cells.

What causes Eumycotic Mycetoma and what characterizes it?

Caused by various fungi; tumor-like deformities of the affected area.

What are key systemic mycoses caused by dimorphic fungi?

Blastomyces dermatitidis; Coccidioides immitis; Histoplasma capsulatum.

What are the characteristic yeast forms for Blastomyces dermatitidis at 37°C?

Large yeast with a broad-based budding (the “lollipop” appearance).

What organism is responsible for San Joaquin Valley Fever and what does its mold form produce?

Coccidioides immitis; thick-walled spherules with endospores; barrel-shaped arthroconidia in mold.

Which dimorphic fungus is associated with Histoplasmosis and what is a key morphologic descriptor?

Histoplasma capsulatum; knobby/tuberculate macroconidia in the mold form.

What is Mucorales’ hyphae characteristic?

Aseptate (coenocytic) hyphae.

Which pathogens are commonly associated with mucormycosis (Zygomycota) and what is a key hyphal feature?

Mucor, Absidia, Rhizopus; aseptate hyphae; known as “lid lifters.”

What family includes Cryptococcus neoformans and which test detects its capsule?

Cryptococcus neoformans belongs to Cryptococcaceae (in practice: Cryptococcus). India ink staining demonstrates the capsule; mucicarmine can also highlight the capsule.

Which test is used to presumptively identify Candida albicans and what is its result?

Germ Tube Test; positive for Candida albicans (and C. dubliniensis).

What is the significance of CHO (carbohydrate) assimilation testing in yeasts?

Determines which carbohydrates the organism can assimilate for growth; indicates metabolic capabilities.

What antibiotics and agents are added to fungal media to suppress unwanted growth?

Chloramphenicol or gentamicin to prevent bacterial overgrowth; cycloheximide to prevent saprophytic fungi.

What is the preferred specimen type and handling for fungal cultures?

Specimens should be processed ASAP; aseptic technique; avoid cotton swabs; some samples may be refrigerated briefly if processing is delayed (except dermatologic samples, blood, CSF).

What is the basic approach to fungal diagnostics (order of tests)?

Specimen -> microscopy (KOH, stains) -> culture -> additional/differential tests (germ tube, CHO assimilation, etc.).

What is the gold standard method for detecting fungal infections and typical incubation time?

Culture; fungi are slow growers; incubation typically 21–30 days at 25–30°C.

What are the three major categories of fungal diagnostics listed?

Microscopy, culture, and additional differential tests (e.g., germ tube, biochemical tests).

What is HIV’s virus family and a defining feature of this family?

Retroviridae; reverse transcriptase; integrate into host DNA; high mutation rates.

Which virus family is the largest and has brick-shaped virions?

Poxviridae (e.g., Variola, Vaccinia); large, brick-shaped virions; enveloped.

What is the common name for the virus that causes varicella and zoster (chickenpox and shingles) and its family?

Varicella-Zoster Virus (HHV-3); Herpesviridae.

Which herpesvirus is most commonly associated with infectious mononucleosis and Burkitt’s lymphoma?

Epstein-Barr Virus (HHV-4; Lymphocryptovirus).

Which herpesvirus is the major cause of CMV disease and is a TORCH agent?

Cytomegalovirus (HHV-5).

Which virus is often detected by the 1-3 beta-D-glucan test as a general fungal marker?

1,3-beta-D-glucan assay (pan-fungal marker).

What chromogenic test helps identify Candida species and what color indicates C. albicans on CHROMagar?

Chromogenic agar for Candida; C. albicans typically shows green colonies.

What is the typical specimen collection guidance for respiratory viruses?

Aspirates or nasopharyngeal/oropharyngeal swabs; swabs better than tissues; collect during acute illness; store at 4°C if delayed.

What receptor is commonly used by SARS-CoV-2 for host cell entry?

ACE2 (Angiotensin-Converting Enzyme 2).

What is the recommended storage condition for viral specimens if processing is delayed beyond 5 days?

-70°C (or lower) to preserve viral integrity.

What type of culture cells are used for viral culture (primary, diploid, continuous) and give an example of each?

Primary cells (e.g., PMK, AGMK); Diploid/PMK-like (HDF, HEF); Continuous cell lines (HeLa, Hep2, A549).

Where do most DNA viruses replicate and which DNA virus family is the notable exception?

Most DNA viruses replicate in the nucleus; Poxviridae is the notable exception (replicates in the cytoplasm).

Where do most RNA viruses replicate, and which two RNA virus groups replicate in the nucleus?

Most RNA viruses replicate in the cytoplasm; Retroviruses and Orthomyxoviruses replicate in the nucleus.

What is the World Health Organization-reported test standard for SARS-CoV-2 confirmation?

RT-PCR for SARS-CoV-2 detection.

Which organisms are known as opportunistic fungi commonly causing meningitis in AIDS patients?

Cryptococcus neoformans; also Aspergillus, Candida, Pneumocystis jirovecii (opportunistic infections listed).

What is Negri body a diagnostic feature of?

Rabies virus (rabies inclusions in neurons).

Which insect-borne viruses are classed under Flaviviridae, and what is a common test for dengue?

Flaviviridae; dengue virus (vector Aedes); NS1 antigen test is commonly used.

What is the classic histological appearance for Histoplasma capsulatum in tissue?

Knobby, tuberculate macroconidia in mold form; yeast forms in tissue within macrophages (Darling’s disease).

Which genus is associated with 'flowerette' conidia arrangement at room temperature and cigar-shaped yeast at 37°C?

Sporothrix schenckii (sporotrichosis).

What is the cornerstone test for diagnosing cryptococcal meningitis in CSF or serum?

Cryptococcal antigen testing and India ink staining of CSF; latex agglutination can also be used.