SM Mycology & Fungal Diagnostics 2

Question 1

Which Aspergillus species accounts for approximately 90% of invasive aspergillosis cases in immunocompromised patients?

Accepted Answer

Aspergillus fumigatus

Answer

Aspergillus fumigatus is the predominant cause of invasive aspergillosis due to its thermotolerance at 37°C, small conidial size enabling deep pulmonary penetration, and abundant environmental distribution.

Question 2

The serum galactomannan enzyme immunoassay (EIA) is an FDA-approved test for diagnosing invasive infection caused by which fungal genus?

Accepted Answer

Aspergillus

Answer

Galactomannan is a cell wall polysaccharide shed by Aspergillus species during active hyphal growth; its detection in serum or BAL is an FDA-approved biomarker for invasive aspergillosis.

Question 3

Blastomyces dermatitidis infection is most commonly acquired through which route?

Accepted Answer

Inhalation of conidia from contaminated soil

Answer

Blastomyces dermatitidis exists as a mold in moist soil and decaying organic matter; infection occurs primarily through inhalation of aerosolized conidia from disturbed environmental sources.

Question 4

Which microscopic finding is most characteristic of Mucormycetes (zygomycetes) in tissue sections or wet preparations?

Accepted Answer

Broad, pauciseptate (rarely septate), ribbon-like hyphae with right-angle branching

Answer

Mucorales (Mucor, Rhizopus, Lichtheimia) characteristically produce broad (10–20 µm), ribbon-like, pauciseptate hyphae that branch at right angles, distinguishing them from the narrow, septate, acute-angle hyphae of Aspergillus.

Question 5

Pneumocystis jirovecii cysts in bronchoalveolar lavage (BAL) specimens are best visualized using which staining method?

Accepted Answer

Gomori methenamine silver (GMS) or calcofluor white

Answer

GMS stain (gold standard) and calcofluor white stain the cyst walls of Pneumocystis jirovecii black and fluorescent respectively, enabling identification in BAL specimens; Giemsa stains trophic forms but not cyst walls.

(SM) Specialist in Microbiology Practice Test

(SM) Specialist in Microbiology Practice Test

SM Mycology & Fungal Diagnostics 2