General Mycology and Overview of Fungal Infections

Flashcards covering general mycology, fungal morphology, classification, laboratory diagnosis methods, and antifungal treatments based on the lecture notes.

Medical Mycology

The branch of medical science that deals with the study of medically important fungi.

Fungus

A term derived from the Greek 'mykes' meaning mushroom.

Chitin

A polysaccharide that, along with $\beta$-glucans, composes the rigid cell wall of fungi.

Ergosterol

A component found in the fungal cell membrane instead of the cholesterol found in human cells.

Mycelium

A branching tangled mass of growth formed by continuously growing hyphae.

Aerial mycelium

The part of the mycelium which projects above the surface of the culture medium.

Vegetative mycelium

The part of the mycelium that grows on the surface of the culture medium.

Yeast

Unicellular fungi that grow as round to oval cells and reproduce by an asexual process called budding.

Pseudohyphae

Chains of elongated cells formed when buds remain attached to the mother cell; they are distinguished from true hyphae by constrictions at the septa.

Molds

Fungi that grow as long branching filaments called hyphae, typically $2-10\,\mu m$ in width.

Septate hyphae

Hyphae that possess transverse walls.

Aseptate hyphae

Hyphae that lack transverse walls and are multinucleated, also known as coenocytic.

Dimorphic fungi

Fungi that exist as molds (hyphal form) at ambient temperature ($25^{\circ}C$) and as yeasts in human tissues at body temperature ($37^{\circ}C$).

Zygomycota

A phylum of lower fungi that possess aseptate hyphae and produce sexual spores known as zygospores.

Ascomycota

A phylum of fungi that possess septate hyphae and produce sexual spores known as ascospores.

Basidiomycota

A phylum of fungi that produce sexual spores known as basidiospores, such as Cryptococcus.

Deuteromycota

Also known as Fungi imperfecti, this group includes fungi where the sexual state is either absent or unidentified.

Potassium hydroxide (KOH) preparation

A method where keratinized tissue specimens are treated with $10\%$ KOH to digest keratin so fungal hyphae can be clearly seen.

India ink and nigrosin stains

Negative stains used for the demonstration of the capsule of Cryptococcus neoformans.

Calcofluor white stain

A sensitive stain that binds to cellulose and chitin in the fungal cell wall and fluoresces under UV light.

Periodic acid schiff (PAS) stain

The recommended primary stain for detecting fungi; live fungi appear magenta/deep pink, while nuclei stain blue.

Gomori methenamine silver (GMS) stain

A stain that detects both live and dead fungi by staining the polysaccharide component of the cell wall black.

Mucicarmine stain

A stain used for identifying the capsular (muciphilic) cell wall of Cryptococcus and Rhinosporidium.

Masson Fontana stain

A stain used for pigmented (phaeoid) fungi, as it detects melanin produced by organisms like Cryptococcus.

Lactophenol cotton blue (LPCB)

A mounting medium containing phenol, lactic acid, glycerol, and cotton blue used to study the microscopic appearance of fungal isolates.

Sabouraud's dextrose agar (SDA)

The most common diagnostic medium in mycology, containing peptone ($1\%$), dextrose ($4\%$), and having a pH of $5.6$.

Corn meal agar

A nutritionally deficient medium used to stimulate the production of chlamydospores in yeasts.

Brain heart infusion (BHI) agar

An enriched medium used for growing fastidious fungi like Cryptococcus and Histoplasma.

Niger seed agar

Also known as bird seed agar, it is used for the selective growth of Cryptococcus.

Slide culture

A technique used to give the most accurate in situ microscopic appearance of a fungal colony by growing it on agar blocks.

Cellophane tape mount

A method for maintaining in-situ fungal morphology by taking impressions of colonies using cellophane tape.

B-d-Glucan assay

An ELISA test for blood antigens that serves as a marker for invasive fungal infections, except for zygomycosis, blastomycosis, and cryptococcosis.

Polyenes

A class of antifungal antibiotics including Amphotericin B, used for systemic mycoses, and Nystatin, used for topical infections.

Echinocandins

A class of antifungals including Caspofungin and Micafungin used for systemic mycoses, primarily those caused by Candida.

Azoles

A class of synthetic antifungal agents divided into Imidazoles (topical) and Triazoles (systemic).