Serum-albumin agar used as slant for the differentiation between Trichophyton rubrum and Trichophyton mentagrophytes: specific reg pigmentation of T. rubrum.

Trichophyton rubrum strains freshly isolated from clinical material exhibited red pigment formation within 7 days at 26 degrees C on slant serum-albumin agar, initial pH 7.0. In Trichophyton mentagrophytes strains this phenomenon could not be observed. Since in the case of T. rubrum, yellow pigmentation will appear at an initial pH of 5.0, the use of initial pH values of 7.0 and 5.0 is recommended for diagnostic application of slant serum-albumin agar.