Aims: Lactobacilli, the predominant micro-organisms of the vaginal microbiota, play a major role in the maintenance of a healthy urogenital tract by preventing the colonization of pathogenic bacteria. The aim of the present study was to assess the ability of four vaginal Lactobacillus strains, previously selected for their probiotic features, to block in vitro the adherence of three human urogenital pathogens to vaginal epithelial cells (VEC). Methods and Results: Three types of assays were performed in order to determine the inhibitory effect of lactobacilli on adhesion of urogenital pathogens to VEC: blockage by exclusion (lactobacilli and VEC followed by pathogens), competition (lactobacilli, VEC and pathogens together) and displacement (pathogens and VEC followed by the addition of lactobacilli). Bacterial adhesion to VEC was quantified by microscopy (×1000) after Gram's stain. All the strains were able to inhibit by exclusion and competition the adhesion of Staphylococcus aureus to VEC but none was able to decrease the attachment of Escherichia coli by neither of the mechanisms assayed. Only Lactobacillus acidophillus CRL 1259 and Lactobacillus paracasei CRL 1289 inhibited the attachment of Group B streptococci (GBS) to VEC by exclusion and competition respectively. Conclusions: Lactobacillus of vaginal origin were able to inhibit the attachment of genitouropathogenic Staph. aureus and GBS to the vaginal epithelium. Significance and Impact of the Study: The results support the probiotic potential of these Lactobacillus strains as anti-infective agents in the vagina and encourage further studies about their capacity to prevent and manage urogenital tract infections in females.

Aims To assess the ability of vaginal lactobacilli to form biofilm under different culture conditions and to determine the relationship between their growth and the capability of biofilm formation by selected strains. Methods and Results Fifteen Lactobacillus strains from human vagina were tested for biofilm formation by crystal violet staining. Only Lactobacillus rhamnosus Centro de Referencia para Lactobacilos Culture Collection (CRL) 1332, Lact. reuteri CRL 1324 and Lact. delbrueckii CRL 1510 were able to grow and form biofilm in culture media without Tween 80. However, Lact. gasseri CRL 1263 (a non‐biofilm‐forming strain) did not grow in these media. Scanning electron microscopy showed that Lact. rhamnosus CRL 1332 and Lact. reuteri CRL 1324 formed a highly structured biofilm, but only Lact. reuteri CRL 1324 showed a high amount of extracellular material in medium without Tween. Conclusions Biofilm formation was significantly influenced by the strain, culture medium, inoculum concentration, microbial growth and chemical nature of the support used for the assay. Significance and Impacts of the Study The results allow the selection of biofilm‐forming vaginal Lactobacillus strains and the conditions and factors that affect this phenomenon.

A novel bacteriocin-like substance produced by vaginal Lactobacillus salivarius subsp. salivarius CRL 1328 with activity against Enterococcus faecalis , Enterococcus faecium , and Neisseria gonorrhoeae was characterized. The highest level of production of this heat-resistant peptide or protein occurred during the late exponential phase. Its mode of action was shown to be bactericidal. L. salivarius subsp. salivarius CRL 1328 could be used for the design of a probiotic to prevent urogenital infections.

Lactic acid-producing lactobacilli were selected from 134 human vaginal isolates by testing their capability to inhibit the growth of different pathogenic micro-organisms. Lactobacillus acidophilus CRL 1259 (from the CERELA Culture Collection) was selected to study the effects of temperature, pH and culture medium on growth and lactic acid production. Growth parameters were estimated by using the model of Gompertz. Kinetics of inhibition of uropathogenic Escherichia coli were evaluated in mixed cultures of the pathogen and L. acidophilus. Optimal conditions for growth and lactic acid production by L. acidophilus were pH 6.5 or 8.0 and 37 °C. Under these conditions, growth was higher in LAPTg (yeast extract/peptone/tryptone/Tween 80/glucose) broth than in MRS (De Man–Rogosa–Sharpe) broth. However, lactic acid production was more efficient in MRS broth. Under optimal conditions for lactic acid production, L. acidophilus inhibited the growth of E. coli. These results suggest that inclusion of L. acidophilus CRL 1259 in probiotic products for vaginal application would be beneficial.