Influence of Lactobacillus crispatus, Lactobacillus iners and Gardnerella vaginalis on bacterial vaginal composition in pregnant women.

PURPOSE: To investigate associations between bacterial species in the vagina in mid-trimester pregnant women from Brazil.

METHODS

The vaginal microbiome in 613 subjects was identified by analysis of the V1-V3 region of bacterial 16S ribosomal RNA and the relative prevalence of individual bacteria were determined.

RESULTS

The bacterial species present in the greatest number of women were Lactobacillus crispatus (306 women), L. iners (298 women) and Gardnerella vaginalis (179 women). When present in the vagina, L. crispatus was the most abundant bacterium more than 85% of the time. In contrast, L. iners and G. vaginalis were most abundant in 63% and 41% of women who were positive for these microorganisms, respectively (p < 0.0001 vs. L. crispatus). The proportion of L. crispatus was negatively associated with the proportions of L. iners, L. jensenii, L. gasseri, G. vaginalis, Megasphaera, Atopobium vaginae and Prevotella (p < 0.0001). In contrast, the proportion of G. vaginalis was positively associated with levels of Megasphaera, A. vaginae and Prevotella (p < 0.0001) while L. iners proportion was unrelated to the proportion of L. jensenii, G. vaginalis, Megasphaera, A. vaginae or Prevotella.

CONCLUSION

The composition of the vaginal microbiota in mid-trimester pregnant women is influenced by the relative concentrations of L. crispatus, L. iners and G. vaginalis.