Prevalence of hydrogen peroxide-producing Lactobacillus species in normal women and women with bacterial vaginosis

TLDR

Normal vaginal flora is dominated by Lactobacillus species, whereas bacterial vaginosis is characterized by increased anaerobes and a reduced prevalence of Lactobacillus. The study aimed to determine whether the lack of hydrogen‑peroxide‑producing Lactobacillus species permits overgrowth of catalase‑negative organisms in bacterial vaginosis. Researchers screened vaginal samples from 28 healthy women and 67 women with bacterial vaginosis for hydrogen‑peroxide‑producing facultative Lactobacillus species. Hydrogen‑peroxide‑producing Lactobacillus were detected in 96 % of healthy women but only 6 % of those with bacterial vaginosis, while anaerobic, non‑H2O2 Lactobacillus were found in 36 % of BV cases versus 4 % of healthy controls, suggesting H2O2 production serves as a nonspecific antimicrobial defense.

Abstract

A predominance of Lactobacillus species in the vaginal flora is considered normal. In women with bacterial vaginosis, the prevalence and concentrations of intravaginal Gardnerella vaginalis and anaerobes are increased, whereas the prevalence of intravaginal Lactobacillus species is decreased. Because some lactobacilli are known to produce hydrogen peroxide (H2O2), which can be toxic to organisms that produce little or no H2O2-scavenging enzymes (e.g., catalase), we postulated that an absence of H2O2-producing Lactobacillus species could allow an overgrowth of catalase-negative organisms, such as those found among women with bacterial vaginosis. In this study, H2O2-producing facultative Lactobacillus species were found in the vaginas of 27 (96%) of 28 normal women and 4 (6%) of 67 women with bacterial vaginosis (P less than 0.001). Anaerobic Lactobacillus species (which do not produce hydrogen peroxide) were isolated from 24 (36%) of 67 women with bacterial vaginosis and 1 (4%) of 28 normal women (P less than 0.001). The production of H2O2 by Lactobacillus species may represent a nonspecific antimicrobial defense mechanism of the normal vaginal ecosystem.