In Vitro Azole Susceptibility of Malassezia globosa Isolates from Healthy Controls, Atopic Dermatitis, and Pityriasis Versicolor Across Anatomical Sites.

Abstract

Malassezia globosa is a major member of the human skin mycobiota and is associated with several cutaneous disorders, yet it remains unclear whether its in vitro azole susceptibility varies with disease status or anatomical site. We evaluated 55 M. globosa isolates obtained from five healthy controls, five patients with atopic dermatitis (AD), and five patients with pityriasis versicolor (PV). Isolates were collected from the forehead, posterior neck, and antecubital fossa in all participants, with additional lesional isolates from AD and PV. Minimum inhibitory concentrations (MICs) were determined for fluconazole, ketoconazole, itraconazole, posaconazole, voriconazole, and isavuconazole. Fluconazole showed the broadest MIC range (0.5-64 μg/mL), whereas posaconazole and voriconazole showed lower ranges (0.00375-0.5 μg/mL). Mixed-effects analyses of the three shared non-lesional sites detected no significant disease-group, site, or disease-by-site effects for any drug (all p > 0.05). Repeated-measures analyses within AD and PV likewise found no significant overall site effect when lesional skin was included. These exploratory data indicate substantial inter-isolate heterogeneity but no consistent association between M. globosa azole susceptibility and clinical group, anatomical site, or lesional status. Larger standardized and strain-resolved studies are warranted.