Medical Mycology Lecture Notes

Vocabulary flashcards covering fungal taxonomy, morphology, reproductive structures, laboratory identification methods, and clinical manifestations of dermatophytes as presented in the lecture transcript.

Mycology

The study of fungi.

Saprobes

Organisms that rely on decaying vegetation and plants for sources of nitrogen; also referred to as saprotrophs.

Mycoses

Fungal infections acquired through inhalation, direct contact with spores, or inoculation by trauma into the skin.

Thallophytes

Heterotrophic members of the plant family that have true nuclei but lack stems and roots.

Dimorphic fungi

Fungi that demonstrate two phases: a yeast phase growing at $35\text{-}37^\text{o}C$ and a mold phase growing at $25^\text{o}C$.

Mycelium

An intertwining structure composed of tubular filaments known as hyphae, forming the microscopic units of fungi.

Septate hyphae

Hyphae that contain cross-walls or septa with pores that facilitate the movement of organelles and nutrients between segments.

Aseptate hyphae

Continuous hyphae without cross-walls; also known as coenocytic hyphae.

Vegetative mycelium

The portion of the thallus that grows in or on a substrate to absorb water and nutrients.

Aerial mycelium

The reproductive part of the mycelium that extends above the agar surface and contains fruiting bodies producing conidia or spores.

Pseudohyphae

Chains of budding cells that are constricted at the septa and form branches starting at the septation, resembling true hyphae.

Chitin

A polysaccharide of N-acetyl glucosamine that composes the fungal cell wall layer located on the cell membrane.

Perfect fungi

Fungi that exhibit a sexual phase involving fertilization or nuclear fission.

Imperfect Fungi

Also known as Fungi imperfecti or Deuteromycetes; fungi that do not exhibit a sexual phase and produce spores asexually.

Teleomorph

The sexual structure of a fungus.

Anamorph

The asexual structure of a fungus.

Holomorph

The whole fungus, including both sexual and asexual structures.

Conidiophores

Specialized vegetative hyphae that produce asexual spores called conidia either singly or in clusters.

Blastic conidiogenesis

A form of conidia formation where the parent cell enlarges, a septum forms, and the large portion splits off to form a daughter cell.

Thallic conidiogenesis

A form of conidia formation where the septum forms first, and new growth beyond the septum becomes the daughter cell.

Macroconidia

Large, usually septate, multicellular asexual spores that can be club, oval, or spindle-shaped.

Microconidia

Small, unicellular asexual spores that are elliptical or pyriform (pear) in shape.

Blastoconidia

Asexual spores that develop as a daughter cell buds off the mother cell and is pinched off, common in yeasts like Candida.

Chlamydoconidia

Thick-walled, resistant resting spores produced by the rounding up and enlargement of terminal hyphal cells.

Arthroconidia

Asexual spores formed by the simple fragmentation of the mycelium at the septum into rectangular, cylinder, or cask-shaped units.

Sporangiospores

Asexual spores contained in a sac called a sporangium, unique to the Zygomycetes group.

Germ tube

Young hyphal-like extensions of yeast cells that develop without constriction at the point of origin; typically $3$ to $4$ times the length of the original cell.

Spherule

A structure seen in tissues infected by Coccidioides posadasii that is filled with endospores.

KOH Preparation

A microscopic method using Potassium Hydroxide to dissolve keratin in skin, hair, and nail specimens to reveal fungal elements.

Wood’s Lamp

A diagnostic tool using long-wave ultraviolet light used to detect fungal skin or scalp infections, as certain fungi will glow or fluoresce.

Saboraud Dextrose Agar (SDA)

The main general isolation medium for fungi, containing peptone and glucose as carbon and nitrogen sources.

Dermatophyte Test Medium (DTM)

A selective medium for recovering dermatophytes; they produce alkaline metabolites that change the pH indicator from yellow to red.

Phaeohyphomycoses

A category of subcutaneous mycoses that usually do not disseminate.

Tinea

Also known as ringworm; a superficial fungal infection characterized by a red, scaly ring-like appearance with a distinct margin.

Favic chandeliers

Characteristic antler or "nail head" hyphae observed in cultures of Trichophyton schoenleinii.

Ectothrix

A fungal infection where mycelia and arthroconidia are seen on the surface of the hair shaft (extrapilary).

Endothrix

A fungal infection where hyphae and arthroconidia occur within the hair shaft (intrapilary).

Favus

A chronic type of tinea capitis where dense yellow cup-shaped crusts (scutula) develop in the hair follicles, leading to alopecia and scarring.

Kerion

A severe, boggy inflammatory reaction of the scalp sometimes developing in dermatophytosis infections.

Tinea versicolor

A superficial infection caused by Malassezia furfur, characterized microscopically by a "spaghetti and meat balls" appearance.

Sclerotia

Hardened masses of hyphae that serve as survival structures for Ascomycetes and Basidiomycetes when nutrients are low.