Intra- and inter-laboratory comparison of mDixon and FastFung broths for Malassezia antifungal susceptibility testing.

BACKGROUND: Malassezia spp. antifungal susceptibility testing (AFST) capacities are limited by the lack of efficient and standardised AFST procedure, mainly because of the fastidious cultivation of these yeast. OBJECTIVES: This study aimed to compare the FastFung broth (FFB) to modified Dixon broth (mDIXB) for the in vitro AFST of Malassezia spp. Fluconazole, ketoconazole, voriconazole and terbinafine MICs against a 19 Malassezia strains, including 6 M furfur, 4 M pachydermatis, 5 M sympodialis and 4 M slooffiae. METHODS: The essential agreement (EA) between the two assays, and the intra- and inter-laboratory agreement of each assay were assessed. RESULTS: The MIC data obtained in our study were comparable to those reported in the literature. FFB showed to enhance Malassezia growth and displayed 100% (±2-fold dilution) EAs demonstrating similar performances to mDIXB. In addition, the MIC data obtained by using the FFB were reproducible between laboratories with EAs ranging from 94.7% to 100%. CONCLUSIONS: Therefore, FFB is a suitable alternative to mDXB for Malassezia spp. AFST.