Lactobacillus species isolated from the vagina: identification, hydrogen peroxide production and nonoxynol-9 resistance

Lactic acid production is considered to be the major protection mechanism of lactobacilli against vaginal infections due to genital pathogens. Some species of Lactobacillus are also hydrogen peroxide (H(2)O(2)) producers. Nonoxynol-9 (N-9) is a nonionic detergent and is the active component of many spermicidal preparations. It immobilizes sperm by disrupting the cell membrane and is believed to act similarly on a number of bacteria and viruses. It is known that N-9 inhibits Lactobacilli in vitro at concentrations of 0.1% to 1%.

The present study was conducted to identify the species of Lactobacillus isolated from vaginal fluids of reproductive-age women and to characterize the H(2)O(2)-producing and N-9-resistant strains in an Argentine population.

We identified Lactobacillus acidophilus, L. fermentum, L. gasseri, L. jensenii, L. casei subsp. casei, L. brevis and L. delbrueckii subsp. delbrueckii as the most frequent species. In this Argentine, South American population, 62% of women had H(2)O(2)-producing vaginal lactobacilli. We found a high number of sensitive strains. Sixty-two H(2)O(2)-producer strains were detected, 50 (80.6%) strains were sensitive to N-9 and 12 (19.4%) strains were resistant to the inhibitory effect of N-9.

The vaginal microecologic findings are comparable to those found in other populations and suggest that (1) vaginal microecologic conditions are likely to be similar among Argentine women as in other countries, and (2) N-9 may have deleterious effects as in other populations.