In vitro antifungal activity of topical and systemic antifungal drugs against Malassezia species

Abstract

The strict nutritional requirements of Malassezia species make it difficult to test the

antifungal susceptibility. Treatments of the chronic and recurrent infections associ- ated with Malassezia spp. are usually ineffective. The objective of this study was to

obtain in vitro susceptibility profile of 76 clinical isolates of Malassezia species against 16 antifungal drugs used for topical or systemic treatment. Isolates were identified by restriction fragment length polymorphism. Minimal inhibitory concentrations

(MIC) were obtained by a modified microdilution method based on the Clinical Labo- ratory Standards Institute reference document M27-A3. The modifications allowed a

good growth of all tested species. High in vitro antifungal activity of most tested

drugs was observed, especially triazole derivatives, except for fluconazole which pre- sented the highest MICs and widest range of concentrations. Ketoconazole and itrac- onazole demonstrated a great activity. Higher MICs values were obtained with

Malassezia furfur indicating a low susceptibility to most of the antifungal agents

tested. Malassezia sympodialis and Malassezia pachydermatis were found to be more- susceptible species than M. furfur, Malassezia globosa, Malassezia slooffiae and Malas- sezia restricta. Topical substances were also active but provide higher MICs than the

compounds for systemic use. The differences observed in the antifungals activity and interspecies variability demonstrated the importance to studying the susceptibility

profile of each species to obtain reliable information for defining an effective treat- ment regimen.