Hydrogen peroxide production and resistance to nonoxinol-9 in Lactobacillus spp. isolated from the vagina of reproductive-age women.

Lactic acid production is considered to be the major protection mechanism of lactobacilli against vaginal infections due to genital pathogens. However, some species of Lactobacillus are also hydrogen peroxide-producers. Women, who usually use intrauterine dispositive (IUD) and spermicides such as nonoxinol-9 (N-9) as contraceptive methods, increase the risk of acquiring an urinary tract infection and a bacterial vaginosis; some studies have demonstrated that these compounds alter the normal vaginal biota. It is known that they inhibit lactobacilli in vitro at concentrations of 0.1% to 1% and that they do not have an effect on the growth of Escherichia coli. It is probable that the presence of nonoxinol-9 affects the ecological balance of the vagina by inhibiting the protector lactobacilli. In this study, we identified Lactobacillus acidophilus, L. brevis, L. crispatus, L. fermentii and L. jensenii as the species most frequently isolated from women. Seventy-one hydrogen peroxide-producer strains and 48 strains resistant to the inhibitory effect of nonoxinol-9 were detected. L. brevis showed the highest number of resistant strains.

Identification of anaerobic nonsporeforming gram-positive bacilli by biochemical tests and gas-liquid chromatography.

There are many methods to identify anaerobic nonsporeforming bacilli: histological, bacteriological (biochemical test, microsystem API 20 A), serological, cell wall composition analysis, molecular methods and gas-liquid chromatography (GLC). A comparison between biochemical tests and gas-liquid chromatography was made in this study for the identification of this group of microorganisms. GLC conditions were established with the aid of reference strains. These conditions were then applied to ten strains which were previously identified by biochemical tests. Strains were grown in PYG broth and fermentation end products were analyzed, volatile and non volatile fatty acids. Their qualitative determination was made by comparing the retention time of known standards and the chromatographic pattern of reference strains. In addition, a semiquantitative analysis was made. The results of identification by biochemical tests were: five strains belonged to Actinomyces genus; three were Propionibacterium acnes; one Propionibacterium granulosum and one P. propionicum. By the GLC only seven strains were identified: four were Actinomyces and three P. acnes. Only six strains showed identification correlation by both biochemical tests and GLC. GLC is a presumptive identification method that can be used along with other complementary tests for a definitive identification at genus level.