The Effect of Amino Acids on the Growth of Trichophyton rubrum and Trichophyton verrucosum

Amino acids have different effects on the growth of dermatophytes. Some may encourage growth while others may inhibit it. These effects not only depend on the type of the amino acid but also on the amino acid concentration and type of the dermatophyte. The aim of this study was to investigate the effects of amino acids on the common dermatophytes in Iran. In this experimental study, two common dermatophytes namely Trichophyton verrcusom and Trichophyton rubrum were selected. They were grown on Sabouraud glucose agar media that contained various concentrations of 23 amino acids. The experiment was carried out three times. After two-three weeks, the diameter of the colonies were measured and compared with the controls that had no amino acids added to the Sabouraud glucose media. Data were analyzed by t-student test. SPSS V.9 was used for data analysis. The results showed that L-cysteine hydrochloride, L-cysteine, L-aspartic acid, L-glutamic had the most inhibitory effects on the studied dermatophytes. Trichophyton verrcusom, but not Trichophyton rubrum, was resistant to DL tryptophan. Arginine, Lysine monocholoride and L-methionine had milder inhibitory effects on both dermatophytes. Serine also had moderate inhibitory effect only against Trichophyton verrcusom. Seven amino acids including L-Cystine, Cysteine hydrochloride, Thereonine, Valine, Glutamine, Leucine and Isoleucine have stimulatory effects only on Trichophyton verrcusom in 0.1 gr/dl concentrations. Non of the amino acids mentioned could stimulate the growth of Trichophyton rubrum. This study indicates that Trichophyton verrcusom and Trichophyton rubrum have different sensitivities towards amino acids; this difference being important in regards to DL tryptophan. This difference could be used to differentiate Trichophyton verrcusom.