Antifungal activities of azole agents against the Malassezia species

Abstract

In this paper, we identified 95 Malassezia isolates by morphological and biochemical criteria and assessed the in vitro activity of fluconazole, itraconazole, ketoconazole and voriconazole by broth microdilution against these species using slightly modified Leeming–Notman medium. The Malassezia isolates were identified as M. furfur (74), M. sympodialis (11), M. obtusa (8) and M. globosa (2). The modified Leeming–Notman medium used for susceptibility testing allowed good growth of Malassezia spp. Visual reading of the minimal inhibitory concentration (MIC) was readily achieved until Day 5 of incubation at 32 °C. Although high MIC values of 16 μg/mL for fluconazole were observed in 9.5% of Malassezia isolates, in general these microorganisms were susceptible to all drugs studied. Interestingly, one M. globosa isolate showed high MIC values for voriconazole, itraconazole and fluconazole. For the 95 strains, the MIC ranges were <0.03–4 μg/mL for ketoconazole, <0.03 to >16 μg/mL for voriconazole, <0.125 to >64 μg/mL for fluconazole and <0.03–16 μg/mL for itraconazole. In summary, the good reproducibility and visual readings obtained using modified Leeming–Notman medium suggest that this medium should be proposed for antifungal testing of drugs against Malassezia spp.