Lactic acid bacteria are considered an inexhaustible source of bioactive compounds; indeed, products from their metabolism are known to have immunomodulatory and anti-inflammatory activity. Recently, we demonstrated that Cell-Free Supernatants (CFS) obtained from Lactobacillus (L.) acidophilus, Lactiplantibacillus (L.) plantarum, Lacticaseibacillus (L.) rhamnosus, and Limosilactobacillus (L.) reuteri can impair Candida pathogenic potential in an in vitro model of epithelial vaginal infection. This effect could be ascribed to a direct effect of living lactic acid bacteria on Candida virulence and to the production of metabolites that are able to impair fungal virulence. In the present work, stemming from these data, we deepened our knowledge of CFS from these four lactic acid bacteria by performing a metabolomic analysis to better characterize their composition. By using an untargeted metabolomic approach, we detected consistent differences in the metabolites produced by these four different lactic acid bacteria. Interestingly, L. rhamnosus and L. acidophilus showed the most peculiar metabolic profiles. Specifically, after a hierarchical clustering analysis, L. rhamnosus and L. acidophilus showed specific areas of significantly overexpressed metabolites that strongly differed from the same areas in other lactic acid bacteria. From the overexpressed compounds in these areas, inosine from L. rhamnosus returned with the best identification profile. This molecule has been described as having antioxidant, anti-inflammatory, anti-infective, and neuroprotective properties. The biological significance of its overproduction by L. rhamnosus might be important in its probiotic and/or postbiotic activity.

Epidermolysis bullosa acquisita (EBA) is a rare blistering skin disease induced by autoantibodies directed against type VII collagen. The transfer of antibodies against murine type VII collagen into mice mimics the effector phase of EBA and results in a subepidermal blistering phenotype. Activation of the complement system, and especially the C5a/C5aR1 axis driving neutrophil activation, is critical for EBA pathogenesis. However, the role of the alternative C5a receptor, C5aR2, which is commonly thought to be more immunosuppressive, in the pathogenesis of EBA is still elusive. Therefore, we sought to delineate the functional relevance of C5aR2 during the effector phase of EBA. Interestingly, C5ar2^-/- mice showed an attenuated disease phenotype, suggesting a pathogenic contribution of C5aR2 in disease progression. In vitro, C5ar2^-/- neutrophils exhibited significantly reduced intracellular calcium flux, ROS release, and migratory capacity when activated with immune complexes or exposed to C5a. These functions were completely absent when C5ar1^-/- neutrophils were activated. Moreover, C5aR2 deficiency lowered the ratio of activating and inhibitory FcγRs, impeding the sustainment of inflammation. Collectively, we show here a proinflammatory contribution of C5aR2 in the pathogenesis of antibody-induced tissue damage in experimental EBA.

Candidiasis is common in diabetic patients. Complement evasion is facilitated by binding complement factor H (FH). Since the expression of high-affinity glucose transporter 1 (Hgt1), a FH-binding molecule, is glucose-dependent, we aimed to study its relevance to the pathogenesis of Candida albicans. Euglycemic and diabetic mice were intravenously challenged with either Candida albicans lacking Hgt1 (hgt1-/-) or its parental strain (SN152). Survival and clinical status were monitored over 14 days. In vitro, Candida albicans strains were grown at different glucose concentrations, opsonized with human serum, and checked for C3b/iC3b and FH deposition. Phagocytosis was studied by fluorescein isothiocyanate-labeled opsonized yeast cells incubated with granulocytes. The murine model demonstrated a significantly higher virulence of SN152 in diabetic mice and an overall increased lethality of mice challenged with hgt1-/-. In vitro lower phagocytosis and C3b/iC3b deposition and higher FH deposition were demonstrated for SN152 incubated at higher glucose concentrations, while there was no difference on hgt1-/- at physiological glucose concentrations. Despite C3b/iC3b and FH deposition being glucose-dependent, this effect has a minor influence on phagocytosis. The absence of Hgt1 is diminishing this dependency on complement deposition, but it cannot be attributed to being beneficial in a murine model.

Probiotics are living microbes that provide benefits to the host. The growing data on health promotion, following probiotics administration, increased interest among researchers and pharmaceutical companies. Infections of the lower genital tract in females, caused by a wide range of pathogens, represent one of the main areas for the use of probiotics and postbiotics. Vulvovaginal candidiasis (VVC) affects 75% of women of reproductive age at least once during their lifetime, with 5–8% developing the recurrent form (RVVC). The disease is triggered by the overgrowth of Candida on the vaginal mucosa. Here, in order to establish its probiotic potential in the context of VVC, we evaluated the anti-fungal effects of the spore-producing Bacillus coagulans LMG S-24828 against C. albicans and C. parapsilosis as well as its beneficial effects in counteracting Candida vaginal infection in vitro. Our results show that both live B. coagulans and its Cell-Free Supernatant (CFS) exerted antifungal activity against both fungi. Moreover, live B. coagulans reduced hyphal formation, inhibited C. albicans adhesion to vaginal epithelial cells, showed co-aggregation capacity, and exerted a protective effect on vaginal epithelial cells infected with C. albicans. These data suggest that B. coagulans LMG S-24828 may provide benefits in the context of Candida vaginal infections.

Thermo-tolerance is a virulence factor responsible for the emergence of new fungal pathogens, including Candidozyma auris (formerly classified as Candida auris, C. auris). It has been shown that in C. auris the thermo-tolerance, as well as other virulence traits, such as the ability to aggregate, to form pseudo-hyphae, or to produce melanin are strain-specific features. Here, we investigated the impact of different temperatures (25 °C, 37 °C and 42 °C) on the phenotypic and virulence profile of C. auris strain CDC B11903. The results show a positive correlation between the resistance to antifungals and increasing temperature from 25 °C to 37 °C, while no differences were observed between 37 °C and 42 °C, except for Anidulafungin. Furthermore, C. auris growth was impaired at 25 °C as compared to 37 °C and 42 °C. Except for the haemolytic activity, which increased with rising temperatures, phospholipase, lipase and biofilm production were found at all tested temperatures. Moreover, the ability to produce melanin was observed only at 37 °C and 42 °C. The capacity to grow as pseudo-hyphae or in clusters and to adhere to both biotic and abiotic surfaces were observed at all the temperatures tested, with increased propensity of C. auris to adhere to abiotic surfaces with rising temperatures. The results underline the thermo-tolerance of C. auris strain B11903 and its increased virulence profile at human body temperature both in physiological (37 °C) and febrile state (42 °C).