Abstract
Arthrospores of Trichophyton mentagrophytes were inoculated onto the plantar part of a guinea pig foot by the wet disc inoculation method.
Anthropophilic strain NTM-105 and zoophilic strain SM-110 required 280 arthrospores (or 315 microconidia) and 80 arthrospores to infect 50% of the inoculated feet, respectively. After inoculation of 5×103 arthrospores, all feet were infected, even 50 arthrospores were shown to be infective in some cases.
Some arthrospores of NTM-105 inoculated on plantar parts of guinea pig feet germinated in 6 hours and the hyphae invaded horny cells in 12 hours, but histological examination revealed no fungal elements in the horny layer of 24-hour feet. After 3 days, one-third of the horny layer was invaded by fungi and after 7 days this had increased to two-thirds.
Anthropophilic strain NTM-105 invaded only the upper two-thirds of the horny layer and induced no inflammatory response. On the other hand, zoophilic strain SM-110 invaded the whole horny layer and provoked strong inflammatory response and clinical manifestations.
Infecting fungi were demonstrated in the horny layer of all inoculated feet for more than 6 months.
The experimental infection indicated herein will be a useful model to analyse tinea pedis, because it is quite similar to human tinea pedis histologically, clinically and in terms of its chronicity. Precise experimental studies using this model may open the way to an elucidation of fungal infection mechanisms against host defense activities and an evaluation of antifungal treatments.
