Fungi

Question 1

Anti-fungal mechanisms of action

Answer 1

Polyenes (Amphotericin B, nystatin) – Membrane Disruption
Binds ergosterol in fungal PM to disrupt fungal membrane
Due to similarities to cholesterol, may cause some toxicities
Azoles (Fluconazole, Voriconazole) – Sterol Synthesis Inhibitor
Inhibits ergosterol synthesis – fungi can’t form cell wall
Allylamines (Terbinafine) – Sterol Synthesis Inhibitor
Inhibits squalene epoxidase – earlier step in sterol synthesis
Echinocandins (Micafungins, -fungins) – Glucan Synthesis Inhibitor
Inhibit cell wall glucan synthesis – impairs cell wall stress tolerance
First line for empiric antifungal therapy

Question 2

Pneumocystosis

Answer 2

RF: Assoc. with defects in cellular/humoral immunity
(HIV, malnutrition, corticosteroid therapy)
CS: Pneumonia
H: Cysts, sporozoites (within cysts), trophozoites (free-floating)

Question 3

Candidiasis

Answer 3

RF: Associated with Abx use, HIV/AIDS, neutropenia, chemotherapy, catheters
		CS: Bloodstream Infection, nosocomial, key in outbreaks, developing resistance
                                Mucocutaneous Infection (thrush, white lesions roof of mouth)
		H: Narrow budding yeast, germ-tube = pseudo-hyphi

Question 4

Blastomycosis

Answer 4

RF: North Central US (Chicago)
CS: Pneumonia, noncaseating granuloma
H: Broad-based budding yeast, thermally dimorphic

Question 5

Histoplasmosis

Answer 5

RF: Ohio-Mississippi River Valley (Chicago), Central/South America, SS Africa
Associated with disrupting soil by excavation or construction
CS: Pneumonia, caseating/non-caseating granuloma
H: Small, narrow budding yeast, thermally dimorphic

Question 6

Coccidiodomycosis

Answer 6

Coccidiodomycosis:
RF: Southwest US, Mexico, little South America
CS: Pneumonia
H: Endospores, spherules, thermally dimorphic

Question 7

Mucormycosis

Answer 7

Mucormycosis:
RF: Associated with Diabetes, Neutropenia, Transplantation
CS: Pneumonia
H: Broad, non-septate hyphae, right-angle branching