A clinical isolate of Trichophyton mentagrophytes which produces a diffusible red-brown pigment as well as typical microconidia en grappe and abundant spirals on Sabouraud's Dextrose Agar has been studied. It splits urea and perforates hair in vitro but does not produce pigment on cornmeal agar or require vitamins for growth. A low molecular weight, red pigment, partially purified from culture filtrates by gel-filtration, was characterized as 2-carboxy 2,3-dihydroindole-5,6-quinone, an intermediate in melanin biosynthesis. It is water soluble, lacks free amino groups, unstable in alkaline buffers, and has spectral absorption peaks at 320-340 nm and 450-490 nm.
ASJC Scopus subject areas
- Infectious Diseases