A study of the prevalence of hydrogen peroxide generating Lactobacilli in bacterial vaginosis: the determination of H₂O₂ concentrations generated, in vitro, by isolated strains and the levels found in vaginal secretions of women with and without infection

Abstract

The concentration of hydrogen peroxide in the vaginal secretions of normal women were compared with levels found in women infected with bacterial vaginosis (BV). The mean concentration found in 90 normal samples was 0.171 μg per ml, whereas in women with BV, the mean level was 0.04 mug per ml (P < 0.001). In vitro culture experiments using TMB agar showed that in normal women, 75% of Lactobacillus strains produced H₂O₂ and 25% did not, whereas in women 'infected' with BV. 14% of the isolates produced H₂O₂ and 86% did not (P < 0.001). Quantitative culture tests showed that both anaerobic and facultative strains of Lactobacilli isolated from normal women generated significantly higher levels of H₂O₂ than strains cultured from women with BV. Anaerobic strains isolated from normal women produced a mean level of 6.8 μg per ml, compared with the mean level of 1.4 μg per ml from women with BV. Facultative strains from normal women produced mean levels of 18.3 μg per ml compared with 2.4 μg per ml produced by strains from BV-infected women, which had been incubated under the same conditions (P < 0.001). There results indicate that Lactobacilli which produce H₂O₂ probably have a significant role in protecting the vaginal ecosystem from BV infection.