Factors affecting germination of Trichophyton mentagrophytes arthrospores

Nutritional and environmental factors affecting germination of Trichophyton mentagrophytes arthrospores were investigated. Germination of dormant arthrospores occurred only in rich complex media such as Sabouraud dextrose broth or vitamin-free Casamino Acids. However, once activated, arthrospores were able to germinate under wide ranges of pH (5.5 to 8.0, optimal 6.5) and temperature (20 to 39 degrees C, optimal 37 degrees C) in the presence of certain single amino acids or oligopeptides known to be present in the human cutaneous tissues. Dormant arthrospores could be activated by incubation in distilled water at 25 degrees C for 24 h or by brief exposure to sublethal doses of heat (45 degrees C for 10 to 20 min). Approximately 20% of activated arthrospores underwent spontaneous germination at 37 degrees C during an additional 18 h of incubation in distilled water. All monosaccharides, purines, pyrimidines, and nucleosides tested failed to induce germination of T. mentagrophytes arthrospores. Germination rate was affected by the concentration of germination inducers as well as that of arthrospores. The germination process of T. mentagrophytes arthrospores was found to be oxygen dependent and was relatively tolerant to NaCl, clotrimazole, cycloheximide, griseofulvin, and tolnaftate.