EXPERIMENTAL PENETRATION OF TRICHOPHYTON-MENTAGROPHYTES INTO HUMAN STRATUM-CORNEUM

We present confirmation of the experimental penetration of Trichophyto n mentagrophytes into human stratum corneum under designated condition s of temperature and humidity. When stratum corneum, obtained from hea lthy human heel region, was incubated at 100% humidity, mycelium was o bserved in the corneum layer on day 2 at 35 degrees C and 27 degrees C , and on day 4 at 15 degrees C. At 90% humidity, the hyphae penetrated into the stratum corneum on day 4 at 35 degrees C, and on day 6 at 27 degrees C. Whereas, at 80% humidity, no fungal elements were observed in the stratum corneum at both 27 degrees C and 35 degrees C for up t o 7 days. These data suggested that humidity was a more important envi ronmental factor for penetration than temperature, and that at least 9 0% humidity is necessary for dermatophytes to penetrate into the strat um corneum within a few days. Mean humidity in the interdigital space between the fourth and fifth toes was found to be approximately 98%.