Identification of four types of vaginal microbiota in pregnant Korean women with abnormal vaginal flora

Objective: To analyze vaginal microbial composition of pregnant Korean women and to investigate compositions of vaginal microbiota of those with abnormal vaginal flora. Methods: This prospective cohort study enrolled 212 pregnant Korean women. Vaginal swab samples were collected for Nugent scoring and next-generation sequencing (NGS) analysis. Among the 212 subjects, 175 subjects had normal flora (NF), 20 subjects had intermediate flora (IF), and 17 subjects had bacterial vaginosis (BV). Metagenomic DNA was extracted and amplified by polymerase chain reaction for NGS. The relative abundance of the vaginal microbiota was calculated and represented using a heatmap. Microbial composition was compared among the groups based on species richness and diversity. Results: Five major community types and other smaller groups were analyzed in the vaginal microbiota. While the NF group was dominated by one or two Lactobacillus spp., IF and BV groups had fewer Lactobacillus spp., except for L. iners, and showed higher bacterial diversity than that of the NF group. Principal coordinate analysis indicated that the NF group was significantly different from IF and BV groups (p < 0.05). However, there was no significant difference between IF and BV groups (p = 0.25). Using a clustering program, IF and BV groups were reclassified into three groups: BV1 (L. iners-predominant), BV2 (decreased alpha diversity and less L. iners), and BV3 (high alpha diversity) groups. The BV2 group had two different microbial compositions: four cases showed Gardnerella vaginalis-predominant microbiota (BV2-2), whereas three cases showed Bifidobacterium breve-dominant microbiota (BV2-1). The four groups (BV1, BV2-1, BV2-2, and BV3) were divided into significantly distinct clusters in principal coordinates analysis (p < 0.05). Conclusion : By NGS analysis, we identified four distinct types of vaginal microbiota in pregnant Korean women with AFV. It may help understand the pathophysiology and establish proper management guidelines for AVF.