Anti-Candida albicans and anti-virulence activities of vaginal Lactobacillus strains from asymptomatic women: phenotypic characterization and prediction of antimicrobial peptide gene clusters

Vulvovaginal candidiasis (VVC) is a prevalent mucosal infection primarily caused by Candida albicans, affecting up to 75% of women of reproductive age. VVC therapeutic management is increasingly challenged by antifungal resistance, host toxicity, and high recurrence rates. Lactobacillus species, the dominant members of healthy vaginal microbiota, are known to antagonize pathogens and maintain mucosal homeostasis by producing antimicrobial metabolites and modulating epithelial responses. However, few studies have explored the antagonistic and anti-virulence properties of Lactobacillus strains isolated from asymptomatic women, particularly their activity against clinical C. albicans isolates. This study aimed to characterize vaginal Lactobacillus strains and their cell-free supernatants (CFS) isolated from asymptomatic women and evaluate their antifungal and anti-virulence activities against clinical isolates of C. albicans. Forty-two clinical Lactobacillus isolates were identified, of which eight inhibited the growth of the tested pathogens. However, among the clinical isolates, only L. fermentum JAC 231 and Lactiplantibacillus plantarum MDBL 269 inhibited all the fungal isolates tested. Based on these results, L. fermentum ATCC 23271 (positive control) and the clinical strains L. fermentum JAC 231 and L. plantarum MDBL 269 were selected for detailed analyses of their ability to interfere with key virulence factors of C. albicans, including hyphal morphogenesis, biofilm formation and disruption, adhesion, and the secretion of extracellular enzymes. The selected strains and their CFS displayed antagonistic activity: they reduced pathogen adhesion, co-aggregated with yeast cells, impaired biofilm formation, and destabilized preformed biofilms. In addition, whole-genome sequencing combined with antimicrobial peptide gene-cluster prediction using BAGEL4 and antiSMASH revealed two biosynthetic gene clusters in L. fermentum JAC 231 and seven in L. plantarum MDBL 269, providing a plausible genetic basis for the antimicrobial effects observed.