Improved procedures for differentiating Microsporum persicolor from Trichophyton mentagrophytes.

Microsporum persicolor, a zoophilic dermatophyte species, is seldom recorded causing human infections in North America. Its identification has been enhanced as a direct result of the development of improved techniques for its characterization. Identifying characteristics include induction of rough-walled macroconidia on sodium chloride-amended medium, absence of good growth at 37 degrees C, and absence of a pH change during growth on casein glucose medium. In contrast, Trichophyton mentagrophytes, a species commonly confused with M. persicolor, has smooth-walled macroconidia, grows well at 37 degrees C, and produces an alkaline reaction on casein glucose medium.