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IntroductionAntifungal agents are not always efficient in resolving vulvovaginal candidiasis (VVC), a common genital infection caused by the overgrowth of Candida spp., including Candida albicans, or in preventing recurrent infections. Although lactobacilli (which are dominant microorganisms constituting healthy human vaginal microbiota) are important barriers against VVC, the Lactobacillus metabolite concentration needed to suppress VVC is unknown.MethodsWe quantitatively evaluated Lactobacillus metabolite concentrations to determine their effect on Candida spp., including 27 vaginal strains of Lactobacillus crispatus, L. jensenii, L. gasseri, Lacticaseibacillus rhamnosus, and Limosilactobacillus vaginalis, with inhibitory abilities against biofilms of C. albicans clinical isolates.ResultsLactobacillus culture supernatants suppressed viable fungi by approximately 24%-92% relative to preformed C. albicans biofilms; however, their suppression differed among strains and not species. A moderate negative correlation was found between Lactobacillus lactate production and biofilm formation, but no correlation was observed between hydrogen peroxide production and biofilm formation. Both lactate and hydrogen peroxide were required to suppress C. albicans planktonic cell growth. Lactobacillus strains that significantly inhibited biofilm formation in culture supernatant also inhibited C. albicans adhesion to epithelial cells in an actual live bacterial adhesion competition test.Discussion Healthy human microflora and their metabolites may play important roles in the development of new antifungal agent against C. albicans-induced VVC.

Endometritis has a major impact on fertility in postpartum dairy cows. Since previous studies showed an association between reproductive microbiota and perinatal disease, we monitored both bovine uterine and vaginal microbiota in primiparous cows to elucidate the effect of early postpartum microbiota on endometritis. Uterine and vaginal samples were collected at time points from pre-calving to 35 days postpartum (DPP), and analyzed by 16S rRNA sequencing, combined with ancillary bacterial culture. A total of seven healthy cows and seven cows diagnosed with endometritis on 35 DPP were used in the current study. The uterine and vaginal microbiota showed a maximum of 20.1% shared amplicon sequence variants (ASVs) at linked time points. 16S rRNA based analysis and traditional culture methods revealed that Trueperella showed a higher abundance in both uterus and vagina of the endometritis group compared to the healthy group on 21 DPP (U-test p < 0.05). Differential abundance analysis of the uterine microbiota showed that Enterococcus and six bacterial genera including Bifidobacterium were unique to the healthy group on the day of calving (0 DPP) and 28 DPP, respectively. In contrast, Histophilus and Mogibacteriaceae were characteristic bacteria in the vagina pre-calving in cows that later developed endometritis, suggesting that these bacteria could be valuable to predict clinical outcomes. Comparing the abundances of bacterial genera in the uterine microbiota, a negative correlation was observed between Trueperella and several bacteria including Lactobacillus. These results suggest that building an environment where there is an increase in bacteria that are generally recognized as beneficial, such as Lactobacillus, may be one possible solution to reduce the abundance of Trueperella and control endometritis.