Saccharomyces cerevisiae probiotic properties are effective for the treatment of infections by the opportunistic pathogen Candida albicans. Here, we assessed the anti-Candida effect of cell-free supernatants (CFSs) from three different fecal isolates and one ATCC strain of S. cerevisiae. We evaluated C. albicans growth inhibition through CFUs, and the impairment of virulence factors (adhesion, biofilm formation, and metabolic activity) by crystal violet and XTT assays. An untargeted metabolomic analysis of the CFSs was also performed. The CFSs moderately reduced C. albicans growth, but they could impair C. albicans virulence by reducing its capacity to adhere and to form a biofilm, and by decreasing the metabolic activity of biofilm-embedded fungal cells. The untargeted metabolomic analysis indicated an overexpression of N-acetyl-DL-tryptophan and other molecules derived from its metabolism (kynurenic acid and indole-3-acrylic acid), the dipeptides glycyl-L-leucine, prolyl-leucine, and γ-L-glutamyl-L-leucine, and the unconventional nucleotide inosine in the CFSs from fecal isolates, as compared to the reference strain. Further studies are warranted to better characterize the metabolome of these CFSs. Should the effects described here also be confirmed in vivo, the possible future employment of S. cerevisiae CFSs as a postbiotic aid to the current antifungal therapy may be considered.

Urinary tract infections (UTIs) are among the most common bacterial infections and represent a significant health concern worldwide. The most common cause of these infections is the Gram-negative bacterium Escherichia coli (E. coli), an opportunistic commensal of the human gut that can shift to pathogenicity, leading to a wide variety of diseases. The increasing ability of E. coli to develop resistance to various classes of antibiotics underscores the urgent need for alternative approaches to clear up infections caused by this species. In this study, we analyzed the possible beneficial role of Heyndrickxia coagulans (H. coagulans) strain LMG S-24828 in an in vitro model of T24 urothelial cells infection by ESBL-producing E. coli. Our results showed that H. coagulans LMG S-24828 was able to: (i) reduce E. coli growth; (ii) impair E. coli adhesion to T24 urothelial cells; and (iii) modulate cytokine production by T24 urothelial cells per se and after E. coli infection. Collectively, these findings indicate a beneficial effect of H. coagulans strain LMG S-24828 against an ESBL–E. coli isolate in an in vitro model of T24 urothelial cell infection.