title: Antifungal Susceptibility Testing of Malassezia spp. with an Optimized Colorimetric Broth Microdilution Method.
abstract: Malasseziais a genus of lipid-dependent yeasts. It is associated with common skin diseases such as pityriasis versicolor and atopic dermatitis and can cause systemic infections in immunocompromised individuals. Owing to the slow growth and lipid requirements of these fastidious yeasts, convenient and reliable antifungal drug susceptibility testing assays forMalasseziaspp. are not widely available. Therefore, we optimized a broth microdilution assay for the testing ofMalasseziathat is based on the CLSI and EUCAST assays forCandidaand other yeasts. The addition of ingredients such as lipids and esculin provided a broth medium formulation that enabled the growth of allMalasseziaspp. and could be read, with the colorimetric indicator resazurin, by visual and fluorescence readings. We tested the susceptibility of 52 strains of 13Malasseziaspecies to 11 commonly used antifungals. MIC values determined by visual readings were in good agreement with MIC values determined by fluorescence readings. The lowest MICs were found for the azoles itraconazole, posaconazole, and voriconazole, with MIC90values of 0.03 to 1.0 μg/ml, 0.06 to 0.5 μg/ml, and 0.03 to 2.0 μg/ml, respectively. AllMalasseziaspp. were resistant to echinocandins and griseofulvin. SomeMalasseziaspp. also showed high MIC values for ketoconazole, which is the most widely recommended topical antifungal to treatMalasseziaskin infections. In summary, our assay enables the fast and reliable susceptibility testing ofMalasseziaspp. with a large panel of different antifungals.
authors.affiliation: Department of Dermatology, University and University Hospital of Zurich, Zurich, Switzerland.
authors.forename: Cheryl
authors.initials: C
authors.lastname: Leong
authors.affiliation: Department of Dermatology, University and University Hospital of Zurich, Zurich, Switzerland.
authors.forename: Antonino
authors.initials: A
authors.lastname: Buttafuoco
authors.affiliation: Department of Dermatology, University and University Hospital of Zurich, Zurich, Switzerland martin.glatz@usz.ch philipp.bosshard@usz.ch.
authors.forename: Martin
authors.initials: M
authors.lastname: Glatz
authors.affiliation: Department of Dermatology, University and University Hospital of Zurich, Zurich, Switzerland martin.glatz@usz.ch philipp.bosshard@usz.ch.
authors.forename: Philipp P
authors.initials: PP
authors.lastname: Bosshard
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D003124:Colorimetry / Q000379:methods*; D006801:Humans; D008290:Malassezia / Q000187:drug effects*; D008826:Microbial Sensitivity Tests / Q000379:methods*; D010078:Oxazines / Q000032:analysis; D014966:Xanthenes / Q000032:analysis
chemical_list: D000935:Antifungal Agents; D010078:Oxazines; D014966:Xanthenes; C005843:resazurin
keywords: Malassezia; antifungal agents; antifungal susceptibility testing; fungi; yeasts