Skip to Main Content

Which of the following is not a dimorphic fungal organism?

A. Blastomyces dermatitidis

B. Cryptococcus neoformans

C. Histoplasmosis capsulatum

D. Penicillium marneffei

E. Sporothrix schenckii

B. Cryptococcus neoformans is not a dimorphic fungus. It produces only a yeast form and causes systemic disease in immunocompromised persons. The remainder of the species, including Penicillium marneffei, is dimorphic species.

Which fungus produces characteristic barrel-shaped arthroconidia that are easily aerosolized, and of particular exposure-danger to laboratory workers?

A. Blastomyces dermatitidis

B. Coccidiomycosis immitis

C. Histoplasmosis capsulatum

D. Paracoccidioides brasiliensis

E. Sporothrix schenckii

B. Coccidioides immitis is a fungus that produces barrel-shaped arthroconidia with alternating empty spaces that are easily spread through aerosolization. Once inhaled arthroconidia transform into spherules containing endospores. Therefore, cultures forming arthroconidia may be dangerous to lab personnel. The disease flourishes in the Lower Sonoran Desert life zone of the southwestern United States. Latex particle agglutination and immunodiffusion test are positive in 90% of cases in early phase of the disease.

What dermatophyte is a common cause of tinea cruris, but does not cause tinea capitis?

A. Epidermophyton floccosum

B. Microsporum audouinii

C. Microsporum canis

D. Trichophyton rubrum

E. Trichophyton tonsurans

A. Epidermophyton floccosum is a common cause tinea cruris, but it does not cause tinea capitis. The most common cause of tinea capitis in the United States is Trichophyton tonsurans.

Which organism may cause extracellular asteroid bodies, with yeast surrounded by brightly eosinophilic spicules?

A. Blastomyces dermatitidis

B. Coccidiomycosis immitis

C. Histoplasmosis capsulatum

D. Paracoccidioides brasiliensis

E. Sporothrix schenckii

E. Sporothrix schenckii is a dimorphic organism, which in tissue forms rare cigar-shaped yeast. The yeast may be encrusted by eosinophilic material yielding an extracellular "asteroid body." This extracellular form of an asteroid body differs from that of Lacazia loboi, the causative species of lobomycosis, which forms intracellular asteroid bodies within histiocytes.

...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.