Griseofulvin-Sabouraud Agar Test in the Differentiation of Trichophyton Mentagrophytes and Trichophyton Rubrum

Abstract

Griseofulvin is exquisitely fungistatic for T. rubrum, while on the other hand, T. mentagrophytes does not have high sensitivity to this antibiotic. Therefore, as Dr. Schwarz suggested, griseofulvin can be used to differentiate these two fungi. After dissolving 100 mg of griseofulvin in 25 cc of aceton and adding 75 cc of distilled water gradually, the solution of 1000 γ/cc concentration was prepared. Mixing this solution with Sabouraud dextrose agar, 25, 50, 100, and 250 γ/cc of Griseofulvin-Sabouraud agar slants shown Fig. 4 were made. Forty-six strains of T. mentagrophytes and 93 strains of T. rubrum were inoculated on those agar slants and cultivated at room temperature. The observation of their growth and the measurement of their diameter were carried out on the 15th day. Comparing with the control, although the growth of T. mentagrophytes was inhibited, all the strains formed cultures in each of the various concentrations, even in the saturated medium of over 500 γ/cc. On the contrary, the growth of T, rubrum was markedly inhibited, only one strain developing a culture of 1 mm diameter in 100 /cc and none of the 93 strains showed any growth in 250 γ/cc. From these observations it is concluded that T. mentagrophytes and T. rubrum may be differentiated readily by the growing results in two weeks on Sabouraud dextrose agar containing over 250 γ/cc of griseofulvin or saturated Griseofulvin-Sabouraud agar. This method is worth performing as one of the differentiating methods along with others such as pigment production test on corn meal dextrose agar and hair perforation test using in vitro hair culture.