No abstract

Lactobacilli are believed to contribute to the control of the vaginal microflora by different mechanisms such as production of antagonistic substances like lactic acid, bacteriocins, and H2O2. This paper describes the selection of H2O2-generating lactobacilli among 35 hydrophobic isolates from the human vagina. Lactobacillus crispatus F117, which generated the highest H2O2 level, was chosen to study: (a) the kinetics of H2O2 production considering different culture conditions, and (b) the effect of this metabolite on the growth of urogenital tract pathogens. The levels of H2O2 in L. crispatus supernatant increased during its growth and were maximum at the early stationary phase (3.29 mmol H2O2 L-1) under aerated conditions (agitated cultures). In nonagitated cultures there were no detectable levels of H2O2. L. crispatus F117 spent supernatant inhibited Staphylococcus aureus growth in plaque assay. Inhibition was due to H2O2 since catalase treatment of the supernatant suppressed inhibition. In mixed cultures performed with L. crispatus and S. aureus a significant decrease in pathogen growth was observed. The inhibitory effect depended on the initial inoculum of S. aureus. Further evaluation of the properties of L. crispatus F117 will be performed to consider its inclusion in a probiotic for local use in the vaginal tract.

A novel bacteriocin-like substance produced by vaginalLactobacillus salivarius subsp. salivarius CRL 1328 with activity against Enterococcus faecalis,Enterococcus faecium, and Neisseria gonorrhoeaewas 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 bacteria are the dominant bacteria of the vaginal tract in healthy women. Lactobacillus species form a barrier population that protects from pathogen colonisation by mechanisms that include adhesion to epithelial surfaces, self-aggregation and co-aggregation. In this study, factors involved in the self-aggregating ability of vaginal lactobacilli and in the co-aggregation of these microorganisms with Candida spp. are studied. Both self-aggregation and co-aggregation are monitored quantitatively by the decrease in the absorbance of suspensions of the microorganisms and qualitatively by light microscopy. The self-aggregating ability of four vaginal lactobacilli was shown to be caused by a peptide or protein sensitive to trypsin. However, in self-aggregating Lactobacillus acidophilus CRL 1294 the factor was resistant to trypsin and sensitive to pepsin. Among self-aggregating lactobacilli, L. acidophilus CRL 1294 and L. salivarius CRL 1328 were able to co-aggregate with Candida spp. The co-aggregating factor for both strains proved to be peptide of the surface and a peptide on the bacterial surface, while the receptor on the yeast was a carbohydrate. Co-aggregation of both lactobacilli and Candida spp. was inhibited by the addition of mannose but was not affected by other carbohydrates. Self and co-aggregation factors were not able to induce aggregation in non-aggregating lactobacilli.

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 8C. Under these conditions, growth was higher in LAPTg (yeast extract/peptone/tryptone/Tween 80/glucose) broth than in MRS (De ManRogosa-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.