Malassezia isolated from patients with PV exhibits resistance features supporting its pathogenic nature

Malassezia is a lipophilic yeast and a major commensal associated with the human skin and gut. It is responsible for several dermatological conditions and has been associated with human diseases, including certain cancers, yet the factors that trigger pathogenicity in this otherwise benign yeast remain poorly defined. Out of the 21 species of Malassezia that have been identified, 14 are associated with humans. In this study, we investigated how clinical strains of Malassezia furfur differ from the standard laboratory strain in terms of pathogenicity-associated elements and resistance features. In this study, we examined 58 pityriasis versicolor (PV) cases, presented with multiple hyperpigmented scaly macules over different parts of the body. From those infected lesions, skin scrapings were isolated and grown on lipid-rich media. We examined M. furfur strains isolated from PV patients and shortlisted six strains exhibiting pronounced pathogenic characteristics compared against the standard strain (MTCC1374/CBS1878). A comprehensive analysis was performed to assess growth kinetics, biofilm-forming capacity, lipase production, and tolerance to temperature, pH, and salinity. Our results indicate that the clinical variants of M. furfur reveal altered features, including increased biofilm formation, increased lipase production, and the ability to withstand several key parameters like pH, salinity, and temperature, which are indicative of their ability to withstand harsh environmental conditions. These characteristics represent clear signatures of increased pathogenic potential compared to the standard strain that collectively reflect an enhanced ability to withstand the fluctuating microenvironment of the human skin. The emergence of resistance-like features among clinical isolates may explain persistent colonisation and relapse frequently observed in PV and other Malassezia-associated disorders. This work highlights the importance of understanding how a common commensal yeast evolves virulence and resistance features, which may contribute to recurrent infections and confer therapeutic challenges.