Characterization of the vaginal microbiota of Japanese women

The composition of vaginal microbiota changes throughout life in response to health status, sexual activity, and pregnancy. Here the constitution of the vaginal microbiota among non-pregnant women, pregnant woman, and commercial sex workers (CSWs) in Japan were compared. Vaginal samples were obtained from 54 women between January 2014 and February 2015 and the microbiota of each was analyzed by 16S metagenomics as well as cluster and diversity analyses to identify differences. In addition, vaginal Lactobacillus spp. were isolated for comparison. Furthermore, data regarding the use of ritodrine hydrochloride by pregnant women was collected from medical charts. The vaginal microbiota were clustered into three groups. Group 1 was most often dominated by Lactobacillus spp., whereas groups 2 and 3 included not only Lactobacillus spp. but also Bifidobacterium, Atopobium, Prevotella, and Gardnerella spp., in addition to a few other taxa. In non-pregnant women, the proportions of microbes in groups 1, 2, and 3 were 31.8%, 36.4%, and 31.8%, respectively. In pregnant women, the abundance of group 1 microbes was notably greater than that of groups 2 and 3 (66.7% vs. 12.5% and 20.8%, respectively). In CSWs, the prevalence of group 3 microbes was far greater than that of group 1 (87.5% vs. 12.5%, respectively). The alpha diversity of non-pregnant women was significantly greater than that of pregnant women. The detection rate of live Lactobacillus spp. in CSWs was lower than in pregnant and non-pregnant women (25% vs. 50% and 68.2%, respectively). The vaginal microbiota of most pregnant women (60%) who received ritodrine hydrochloride was not dominated by Lactobacillus spp. These results suggest that there were clear differences in the colonization rate of Lactobacillus spp. among non-pregnant, pregnant, and CSW women groups. In addition, the dominance of Lactobacillus may influence the risk of preterm birth among women who received ritodrine hydrochloride during pregnancy.