In vitro susceptibility testing of dermatophytes: comparison of disk diffusion and reference broth dilution methods.

A total of 56 strains belonging to 4 species of dermatophytes were tested against 10 antifungal drugs by using a modification of the NCCLS (M38-P) standard for filamentous fungi. The minimum inhibitory concentration (MIC) values obtained using the dilution method were compared with the diameters of growth inhibition zones using the disk diffusion method. The antifungals used were itraconazole, fluconazole, ketoconazole, miconazole, sulconazole, oxiconazole, bifonazole, griseofulvin, ciclopiroxolamine, and terbinafine. Relative to the other agents tested, terbinafine possessed the highest antifungal activity against all of the dermatophytes. In contrast, fluconazole was the least active drug. An increase of MIC values was accompanied by a decrease of growth inhibition zone diameter. The disk diffusion method of fungal susceptibility assessment yields data consistent with results obtained from the dilution method. The study suggests the potential value of the disk diffusion method as a convenient alternative method for testing the susceptibilities of dermatophytes.