Mycotic Infections - Session 11

Flashcards covering the fundamentals, structure, reproduction, types, and pathogenesis of mycotic infections as discussed in lecture 11.

Aspergillus

A fungus that mimics Marek’s (a serious herpesvirus) in chickens.

Sporadic occurrence

Incidence that is infrequent and irregular, though situational high morbidity can occur under specific conditions like dampness or immunosuppression.

Ergosterol

A key component found in fungal cell membranes, differing from the cholesterol in mammal cells, which serves as a primary target for antifungal drugs.

Polyenes

A class of antifungal drugs, such as Amphotericin B and Nystatin, that kill fungi by binding to ergosterol and damaging the cell membrane.

PAS stain and Silver stain

Special stains required for diagnosis to highlight the polysaccharide components (chitin, mannan, cellulose) of the fungal cell wall.

Capsule

A virulence factor found in fungi like C. Neoformans that protects the organism from phagocytosis by immune cells.

Hyphae

Long filaments produced by multicellular fungi (molds) that elongate, branch, and divide.

Mycelium

A tangled network of branching hyphae that appears as fuzzy, cotton-like colonies in an agar culture (confirmatory diagnosis).

Budding

The reproduction method used by unicellular fungi (yeasts) to form moist colonies on agar.

Dimorphic fungi

Fungi that switch between two forms based on temperature: Yeast in the animal ($37\,^{\circ}C$) and Mold in the environment ($\sim 25\,^{\circ}C$).

Candida albicans

The exception to standard dimorphic rules, existing as a mold in the animal host and a yeast in the environment.

Cutaneous mycoses

Fungal skin infections, such as Ringworm.

Subcutaneous mycoses

Fungal infections affecting the dermis, muscle, and fascia, such as Sporotrichosis or Rhinosporidium.

Systemic mycoses

Deep fungal infections caused by opportunists (like Candida albicans) or primary pathogens (like Blastomyces and Histoplasma).

Microsporum canis

An obligate parasite carried by cats that is a causative agent of ringworm.

Iron ($Fe$)

A limited resource in the body that fungi require for growth, which serves to limit fungal multiplication.

Histoplasma

A fungal genus that is an exception to phagocytic defense because it replicates inside macrophages after being eaten.

T Lymphocytes

A major immune defense against fungi that releases cytokines and activates macrophages.

Granuloma

The hallmark of fungal infection; a hard lump of chronic inflammation where the immune system walls off the infection.

Malassezia spp.

The causative agent commonly associated with dog ear yeast infections.