BACKGROUND: Antifungal drug resistance in dermatophytes was first reported shortly after the turn of the millennium and has today been reported in Trichophyton and occasionally in Microsporum, but not in Epidermophyton species. Although drug resistance in dermatophytes is not routinely investigated, resistance in Trichophyton spp. is increasingly reported worldwide. The highest rates are observed in India (36% and 68% for terbinafine (MIC ≥4 mg/L) and fluconazole (MICs ≥16 mg/L), respectively), and apparently involve the spread of a unique clade related to the Trichophyton mentagrophytes/Trichophyton interdigitale complex. OBJECTIVES: The European Committee on Antimicrobial Susceptibility Testing Subcommittee on Antifungal Susceptibility Testing (EUCAST-AFST) has released a new method (E.Def 11.0) for antifungal susceptibility testing against microconidia-forming dermatophytes including tentative MIC ranges for quality control strains and tentative breakpoints against Trichophyton rubrum and T. interdigitale. Here, the details of the new procedure E.Def 11.0 are described. SOURCES: This technical note is based on the multicentre validation of the EUCAST dermatophyte antifungal susceptibility testing method, the mould testing method (E.Def 9.3.2) and the updated quality control tables for antifungal susceptibility testing document, v 5.0 (available on the EUCAST website). CONTENTS: The method is based on the EUCAST microdilution method for moulds but significant differences include: (a) an altered test medium selective for dermatophytes; (b) an altered incubation time and temperature; and (c) a different end-point criterion (spectrophotometric determination) of fungal growth. It can easily be implemented in laboratories already performing EUCAST microdilution methods and has been validated for terbinafine, voriconazole, itraconazole and amorolfine against T. rubrum and T. interdigitale. IMPLICATIONS: This standardized procedure with automated end-point reading will allow broader implementation of susceptibility testing of dermatophytes and so facilitate earlier appropriate therapy. This is important, as resistance is rapidly emerging and largely underdiagnosed.

CIBER de Enfermedades Respiratorias CIBERES Madrid Spain

Clinical Microbiology and Infectious Diseases Department Hospital General Universitario Gregorio Marañón Madrid Spain

Clinical Microbiology Laboratory Attikon University Hospital National and Kapodistrian University of Athens Athens Greece

Department of Clinical Medicine University of Copenhagen Denmark

Department of Clinical Microbiology University Hospital Rigshospitalet Copenhagen Denmark

Department of Medical Microbiology and Infectious Diseases Erasmus MC Rotterdam the Netherlands

Instituto de Investigación Sanitaria Gregorio Marañón Madrid Spain

The EUCAST Development Laboratory Clinical Microbiology Växjö Sweden

Unit of Mycology Department of Microbiological Surveillance and Research Statens Serum Institut Copenhagen Denmark

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