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 standardized 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.