Antifungal Susceptibility Testing of Dermatophytes Using Etest

Kang, Gyo Shin; Suh, Moo Kyu; Ha, Gyoung Yim

Abstract

Background
It is necessary to perform antifungal susceptibility testing of dermatophytes. Etest (AB Biodisk, Sweden) is a rapid, easy-to-perform in-vitro antifungal susceptibility test. Objective: The purpose of this study was to investigate the minimal inhibitory concentration (MICs) of dermatophytes isolated from skin using Etest. Methods: 21 species of dermatophytes (12 strains of T. rubrum, 7 strains of T. mentagrophytes, M. canis and M. gypseum) and two standard strains (Aspergillus flavus KCTC 6905, Aspergillus fumigatus KCTC 6145) were tested MIC endpoints of Etest for itraconazole (ITZ) and amphotericin B (AMB) were read after 72, 96, and 120 hours incubation for each strains on RPMI 1640 agar. Results: MIC of ITZ was 0.12~0.47 microg/mL on T. rubrum, 0.012~1.0 microg/mL on T. mentagrophytes, 0.012 microg/mL on M. canis, and 0.023 microg/mL on M. gypseum. MIC of AMB was 0.094~0.5 microg/mL on T. rubrum, 0.032~1.0 microg/mL on T. mentagrophytes, 0.19 microg/mL on M. canis, and 0.032 microg/mL on M. gypseum. One strain of T. mentagrophytes isolated from patient with tinea pedis showed ITZ-resistant. Conclusion: This study showed that Etest represented a simple and efficacious method for antifungal susceptibility testing of dermatophytes.