Pigment Production in the Differentiation of Trichophyton mentagrophytes and Trichophyton rubrum

Abstract

The pigment production of 50 strains of T. mentagrophytes and 40 strains of T. rubrum was studied on a number of dextrose containing media. Results indicate that not only dextrose, but also the source of N is important in the production of pigment. On corn meal agar + C.P. dextrose there was no pigment produced by any of the T. mentagrophytes strains but 38 of the 40 T. rubrum strains produced the characteristic red-purple color when the pH level ranged from 5.5 to 8. At pH levels below 5.5 only a cream to yellow pigmentation was noted. This also holds true for the casein hydrolysate dextrose agar. On all other media tested pigment production was not appreciably affected at pH levels from 4 to 8.