In vitro antifungal susceptibility of dermatophyte strains causing tinea pedis and onychomycosis in patients with non-insulin-dependent diabetes mellitus: a case-control study

Abstract

The efficacy of antifungal treatment may be reduced and/or delayed in diabetic patients. To date, no study has investigated the in vitro antifungal susceptibility of dermatophytes in this patient group. We aimed to determine the dermatophyte species causing tinea pedis and onychomycosis, and in vitro susceptibility of these dermatophytes to terbinafine, itraconazole, and fluconazole in patients with non-insulin-dependent diabetes mellitus. We compared the findings in diabetic patients with those in non-diabetic individuals. One hundred patients with non-insulin-dependent diabetes mellitus and 100 otherwise healthy controls clinically suspected with tinea pedis and/or onychomycosis were included. Skin scrapings and/or nail clippings were taken and cultured on Sabouraud dextrose agar, mycobiotic agar, and dermatophyte test medium. In vitro antifungal susceptibility tests were carried out according to the Clinical and Laboratory Standards Institute (CLSI) M-38P protocol with some modifications. Fifty-seven samples of 54 diabetics and 50 samples of 50 controls grew dermatophytes. In both groups, Trichophyton rubrum was the most common isolate. Mean MIC values of terbinafine, itraconazole, and fluconazole for all of the isolated dermatophyte strains were similar in two groups (P>0.05). The difference in mean MIC values of three antifungals for T. rubrum and T. mentagrophytes between two groups was not statistically significant (P>0.05). Dermatophyte types causing tinea pedis and onychomycosis, their frequency patterns, and in vitro activity of three antifungals against dermatophytes in diabetics are similar to the non-diabetics. Terbinafine is the most active agent in vitro in both groups.