Germination of Trichophyton mentagrophytes on human stratum corneum in vitro.

The emergence of germ tubes from arthroconidia of Trichophyton mentagrophytes on stripped sheets of stratum corneum from different body areas was measured. Arthroconidia increased in size and started germination by 4 h at 37 degrees C. Germ tubes originated from a point on the arthroconidium surface mid-way between the points of attachment to adjacent conidia. With further incubation arthroconidial germination increased and germ tubes extended across the stratum corneum. Histological staining of transverse sections of infected stratum corneum showed hyphae penetrating longitudinally and perpendicularly through the thickness of the stratum corneum. By 7 days' incubation hyphae started to form arthroconidia thereby completing the vegetative growth cycle of the fungus. Scanning electron microscopy revealed penetration of corneocytes by germ tubes resulting in damage to the corneocyte surface.