Extracellular Vesicles from Kluyveromyces marxianus as Potential Postbiotics Against Candida albicans Vaginal Infections

This study describes extracellular vesicles (EVs) isolated from the culture supernatant of a Kluyveromyces marxianus strain deriving from an artisanal sourdough. Previous work had clearly shown the probiotic properties of the yeast isolate and its antagonistic activities against clinical fluconazole-resistant Candida albicans strains. Characterization of the isolated EVs by nanotracking particle analysis showed they had a mean diameter of 157.7 nm. Proteomic characterization of the purified EVs identified a complex array of 100 proteins. Both C. albicans planktonic growth and biofilm formation were inhibited by K. marxianus EVs, as well as adhesion and invasion of Candida cells in the vaginal epithelial A-431 cells. In the same cell model, K. marxianus EVs exerted an immunomodulatory effect affecting the secretion of pro-inflammatory and anti-inflammatory cytokines. Further, the expression of C. albicans SAP2 and SAP6 genes, coding for two aspartyl proteases involved in the invasion and damage of the epithelial mucosa, was affected by the presence of the yeast EVs. Overall, the results of this study show that K. marxianus EVs retain, at least in part, the beneficial features of the live microorganism, representing a postbiotic cell-free alternative preparation potentially useful for the management of C. albicans vaginal infections.