Vaginal colonization and activity of the probiotic bacterium Lactobacillus fermentum L23 in a murine model of vaginal tract infection

A strain of Lactobacillus, identified as Lactobacillus fermentum L23, was selected from among 100 strains isolated from vaginal swabs of healthy, non-pregnant, pre-menopausal women. L. fermentum L23 was chosen on the basis of its bacteriocinogenic ability and its properties relevant to colonization, i.e. self-aggregation, adherence to vaginal epithelial cells and co-aggregation with bacterial pathogens. The antimicrobial preventative and curative effects produced by the probiotic L. fermentum L23 administered locally against Escherichia coli in a murine vaginal tract infection model were studied. One dose of the human strain L23 containing 10(8) c.f.u. ml(-1) colonized and persisted in the vaginal tract of the female BALB/c mice for 5 days. Infection with the pathogen at 10(6) c.f.u. ml(-1) in the vaginal tract was maintained for more than 7 days. A single dose of L23 administered 24 h pre-infection inhibited E. coli growth on day 3 post-infection, showing the preventative effect displayed by this Lactobacillus strain. Treatment with L. fermentum L23 during the post-infection period showed complete inhibition of pathogen growth from day 5. Thus, this in vivo study indicated that the probiotic bacterium L. fermentum L23 produced both preventative and curative effects on E. coli growth. The beneficial properties and the production of antimicrobial metabolites may act in situ to inhibit a pathogenic micro-organism within the vaginal environment. Strain L23 could be a good natural alternative to other therapies used for genital infections.