Bioinformatics Analysis of Oral, Vaginal, and Rectal Microbial Profiles during Pregnancy: A Pilot Study on the Bacterial Co-Residence in Pregnant Women

Preterm birth (PTB) and threatened preterm labor (TPL), an important pre-PTB state, are major obstetric complications during pregnancy. However, their triggers have not been fully elucidated. The vagina is dominated by Lactobacillus species (categorized as community state types; CSTs I, II, III, and V) or by mixed anaerobes (CST IV). An abundance of the latter is associated with bacterial vaginosis (BV) and BV-triggered PTB/TPL. To identify factors that influence the diversity of vaginal microbiota associated with BV and CST IV (BV-type) bacterial profile, we performed a bioinformatic analysis of the microbial taxa using 16S rRNA amplicon sequencing data of bacterial genome in oral, vaginal, and rectal samples collected from 58 pregnant Japanese women. Interestingly, common residence of BV-associated bacteria in the vagina and rectum was individually detected in the CST IV (non-Lactobacillus dominated) group by species-level Spearman correlation coefficient analysis, suggesting that the rectum acts as a reservoir of BV-associated bacterial species in the CST IV group. The current study provides evidence of bacterial co-residence in vagina and rectum in the non-Lactobacillus dominated group, which could be targeted to reduce the risk of preterm incidence in pregnancy.