Malassezia interaction with a reconstructed human epidermis: imaging studies

Abstract

BackgroundBiofilm formation represents a major microbial virulence attribute especially at epithelial surfaces such as the skin. Malassezia biofilm formation at the skin surface has not yet been addressed. ObjectiveThe present study aimed to evaluate Malassezia interaction with a reconstructed human epidermis (RhE) model. MethodsMalassezia clinical isolates were previously isolated from volunteers with pityriasis versicolor and seborrheic dermatitis. Yeasts of two strains of M. furfur and M. sympodialis were inoculated onto the SkinEthic RHE. The tissues were processed for light microscopy, wide-field fluorescence microscopy and scanning-electron microscopy. ResultsColonization of the RhE surface with aggregates of Malassezia yeasts entrapped in a multilayer sheet with variable amount of extracellular matrix was unveiled by imaging techniques following 24, 48, 72 and 96 hours of incubation. Whenever yeasts were suspended in RPMI medium supplemented with lipids, the biofilm substantially increased with a dense extracellular matrix in which the yeast cells were embedded (not seen in control samples). Slight differences were found in the biofilm architectural structure between the two tested species. ConclusionSkin isolates of M. furfur and M. sympodialis were capable of forming biofilm in vitro at the epidermal surface simulating in vivo conditions. Following 24 hours of incubation, without added lipids, rudimental matrix was barely visible, conversely to the reported at plastic surfaces. The amount of biofilm apparently increased progressively from 48 to 96 hours. A structural heterogeneity of biofilm between species was found with higher entrapment by a denser and more gelatinous extracellular matrix in M. furfur biofilm.