In vitro susceptibility tests of dermatophytes to griseofulvin and imidazole derivatives

Abstract

The sensitivity of dermatophytes (89 'wild' and 38 'collections' strains) to griseofulvin and azole derivatives (clotrimazole, cetoconazole, tioconazole, miconazole, econazole, isoconazole and oxiconazole) was studied using 'in vitro' determinations of minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC). The broth dilution method was used; the antifungal drugs were used in concentrations between 0,05 to 100 μg/ml. The inoculum was (standardized adjusting the suspension to contain) 1,0 to 1,5 X 106 ufc/ml. The MIC and MFC values showed different results for many fungi strains and different concentrations of antifungal agents. The values for clotrimazole varied from 0,1 to 1,56 μg/ml in almost all strains. Higher values were obtained for T. rubrum (12,5 μg/ml) and T. mentagrophytes (25,0 μg/ml). Cetoconazole was the imidazole drag that showed the highest MIC and MFC values, as high as 100,0 μg/ml when tested against the species of T. rubrum, T. mentagrophytes, T. tonsurans and M. gypseum. The antifungal activities of the other imidazole drugs were comparable, the MIC and MFC values varied from 0,10 to 12,5 μg/ml. In relation to griseofulvin, the fungi used in this study, presented two different behaviours: higher MIC and MFC values (12,5 to 100,0 μg/ml) for T. rubrum, T. mentagrophyte, T. tonsurans, T. soudanense, M. canis, M. gypseum and M. persicolor and lower values (0,39 to 3,12 μg/ml) for T. schoenleinii, T. violaceum, E. floccosum, and M. audouinii. E. floccosum, M. canis and T. schoenleinii had higher susceptibilitis to the drugs, (MIC and MFC values varying from 0,05 to 0,20 μg/ml), when compared to T. mentagrophytes, T. rubrum, M. gypseum and T. soudanense. No important differences were observed in file MIC and MFC values for the 'wild' and the 'collection' strains.