Antifungal susceptibility of Malassezia pachydermatis biofilm

Antifungal resistance has been associated with biofi lm formation in many microorganisms, but not yet in Malassezia pachydermatis . This saprophytic yeast can cause otitis and dermatitis in dogs and has emerged as an important human pathogen, responsible for systemic infections in neonates in intensive care units. This study aims to evaluate the in vitro antifungal susceptibility of M. pachydermatis strains, in both their planktonic and sessile forms, to fl uconazole, miconazole, ketoconazole, itraconazole, posaconazole, terbinafi ne and voriconazole using the XTT assay and Clinical and Laboratory Standards Institute (CLSI) microdilution method. The minimum inhibitory concentration (MIC) values recorded for each drug were signifi cantly higher for sessile cells relative to planktonic cells to the extent that 90% of M. pachydermatis strains in their sessile form were classifi ed as resistant to all antifungal agents tested. Data suggest that M. pachydermatis biofi lm formation is associated with antifungal resistance, paving the way towards investigating drug resistance mechanisms in Malassezia spp.