Selection of Vaginal H_2O_2-Generating Lactobacillus Species for Probiotic Use

摘要

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 H_2O_2. This paper describes the selection of H_2O_2-generating lactobacilli among 35 hydrophobic isolates from the human vagina. Lactobacillus crispatus F117, which generated the highest H_2O_2 level. was chosen to study: (a) the kinetics of H_2O_2 production considering different culture conditions, and (b) the effect of this metabolite on the growth of urogenital tract pathogens. The levels of H_2O_2 in L. crispatus supernatant increased during is growth and were maximum at the early stationary phase (3.29 mmol H_2O_2L~(-1)) under aerated conditions (agitated cultures). In nonagitated cultures there were no detectable levels of H_2O_2. L. crispatus F117 spent supernatant inhibited Staphylococcus aurenus growth in plaque assay. Inhibition was due to H_2O_2 since catalase treatment of the supernatant suppressed inhibition. In mixed cultures performed with L. crispatur 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.