Antibiotic Action of Griseofulvin on Dermatophytes

Abstract

The concentrations of griseofulvin required to inhibit growth and to produce the characteristic morphological distortions were determined for dermatophytes (highly sensitive), fungal plant pathogens (moderately sensitive), filamentous nonpathogenic fungi (poorly sensitive(, and for yeasts and Escherichia coli (insensitive). Addition of griseofulvin to small inocula of the dermatophytes Microsporum gypseum and Trichophyton mentagrophytes produced complete and apparently permanent growth inhibition. If the antibiotic was added to actively growing cultures, the inhibition was only temporary, even with the most sensitive dermatophytes. During growth inhibition, griseofulvin temporarily halted the net synthesis of protein and nucleic-acids, and of the amino-acid and nucleotide pools. It decreased substantially the incorporation of C14- uridine or Cl4-thymidine into nucleic-acids of M. gypseum, but not that of Cl4-leucine or C14-valine into protein. With a less sensitive culture, T. mentagrophytes x8, the uptake of uridine was inhibited only to a slight extent; the incorporation of leucine was unaffected. A partial protective effect of purine nucleotides against growth inhibition by griseofulvin was observed with one strain of T. mentagrophytes, but not with another strain or with M. gypseum.