Histopathologic and mycologic aspects of experimental infection of guinea pigs with Microsporum canis

Abstract

Dermatophytosis is a zoonosis in whose etiology the dermatophyte Microsporum canis is frequently involved. The fungus can be transmitted to man by dogs and cats. In the present study, guinea pigs were experimentally inoculated with M. canis and the course of the lesions was evaluated. Inoculation resulted in lesions in 100% of the animals, with a clinical course consisting of an incubation period, an inflammatory and a phase of lesion resolution. The histopathologic evaluation of the skin biopsies revealed the presence of acanthosis, hyperkeratosis, spongiosis and marked dermal edema. M. canis spores and hyphae were detected in histologic sections stained with periodic acid-Schiff. The combination of the fluorescent dyes FD and EB permitted the adequate visualization of viable and dead fungal cells in skin fragments of guinea pigs inoculated with M. canis and the identification of the morphologic characteristics of the cells. This experimental model represents a valuable instrument for the study of the pathogenesis of dermatophytic infection with respect to the evaluation of the efficacy of antifungal drugs, and may also be used for the study of the immunology of dermatophytoses and of dermatophyte morphogenes