Lactobacilli and Bacterial Vaginosis. Species Typing and Content Analysis in the Microbiome

The goal of the study is to analyze changes in the composition of lactobacilli in the vaginal microbiocenosis associated with bacterial vaginosis (BV), with a frequency assessment of the occurrence of individual species. The study involved 40 patients who complained of pathological discharge from the genital tract, with a confirmed diagnosis of BV based on the Amsel criteria. Quantitative assessment and typing of lactobacilli was performed using real-time PCR. All women with BV were found to have lactobacilli in quantities from 0.01 to 100% of the total bacterial mass. When analyzing the distribution of the lactobacilli index (LI), which determines the proportion of lactobacilli in the total bacterial mass, three peaks were identified that corresponded to samples with low, intermediate, and high values. Typing identified four lactobacilli species characteristic of the vaginal microbiocenosis: L. iners, L. crispatus, L. jensenii, and L. gasseri/L. johnsonii. No samples were found that did not contain at least one of these species, with L. crispatus and L. iners being the most common. Despite the general tendency toward a decrease in the LI level in BV, the patients were divided into three subgroups: with high, moderately reduced, and low LI values. In our opinion, the identified positive correlation for L. iners and a negative one for L. crispatus, with the degree of dysbiosis, does not reflect direct cause-and-effect relationship with respect to BV, since correlations are observed not so much with the clinical manifestations of the disease as with the concentration of lactobacilli. A significant proportion of BV cases with preserved dominance of lactobacilli suggests the existence of at least two forms of this syndrome. One of them, despite the presence of clinical signs, is not associated with a decrease in the number of lactobacilli in the vaginal biocenosis.