Selection and Characterization of Vaginal Lactobacilli from Healthy Algerian Women with Potential Probiotic Properties Against Urogenital Pathogens

Background: The vaginal microbiota of healthy women is predominantly composed of lactic acid bacteria (LAB), particularly species from the lactobacilli group, which contribute to the maintenance of vaginal health through multiple protective mechanisms. Objectives: In the present study, vaginal LAB isolated from healthy premenopausal Algerian women were evaluated for their probiotic potential. Methods: A total of 259 LAB isolates were initially screened for antimicrobial activity against vaginal pathogens, among which 164 strains exhibited inhibitory effects. Based on antimicrobial capacity and biofilm formation ability, 38 strains were selected for further characterization. A refined subset of 15 strains belonging to Lactiplantibacillus (Lpb.) plantarum, Limosilactobacillus (Lmb.) fermentum, and Ligilactobacillus (Lgb.) salivarius were subsequently identified according to their superior antimicrobial and probiotic-related properties. The selected strains were evaluated for several functional and safety characteristics, including antimicrobial activity, production of lactic acid and hydrogen peroxide (H2O2), biofilm formation, auto-aggregation, cell surface hydrophobicity, antibiotic susceptibility, hemolytic activity, and tolerance to acidic conditions. These studies were complemented with comparative genomics using the complete genome sequences of selected strains. Results: The isolates demonstrated significant inhibitory activity against vaginal pathogens associated with aerobic vaginitis, and vulvovaginal candidiasis. In addition, strong correlations were observed between metabolite production and antimicrobial activity. Several strains also exhibited enhanced biofilm formation, aggregation capacity, and favorable safety profiles. Among the tested isolates, Lmb. fermentum 70BJ2, Lpb. plantarum 87JG8, and Lpb.plantarum N17 emerged as particularly promising probiotic candidates due to their combined antimicrobial, metabolic, and adhesion-related properties. Conclusions: Overall, these findings demonstrate that the vaginal microbiota of healthy Algerian women represents a valuable source of potential probiotic strains and provide a strong basis for future in vivo validation and clinical application in the prevention and management of vaginal infections.