A patient made a self-diagnosis of athlete's foot (tinea pedis) and began using a product adveised on television. The condition improved but did not clear and then the patient showed himself to a Dermatologist. A skin scraping was sent to the laboratory for culture, including culture for fungi. The fungal culture yielded a slow growing colony, which produced a few small microconidia. This is consistent with isolation of a dermatophyte of the genera -

Ans. is 'a' i.e., Trichophyton . Dermatophytes can be identified by their colonial appearance and microscopic morphology after growth for 2 weeks at 25degc on sabouraud's dextrose agar. . Differential diagnosis of Dermatophytes on the basis of Macroconidia and microconidia General Microconidia Macroconidia Trichophyton Abundant microconidia, arranged in clusters along hyphae Relatively scanty, elongated with blunt ends Microsporum Single microconidia (multicellular) Single macroconidia (multicellular) Epidermophyton No microcondia Macroconidia in groups of 2 or 3