妊娠後期のB群溶血性レンサ球菌保菌の有無における膣および腸内細菌叢の比較特性評価

Group B Streptococcus (GBS) colonization during pregnancy is a major cause of neonatal infection, yet its microbial determinants remain unclear. This pilot study compared the vaginal and gut microbiota of late-pregnancy women with and without GBS colonization to explore potential microbial cues for peripartum risk stratification. Forty-three Japanese pregnant women (GBS-Negative = 34; GBS-Positive = 9) were enrolled at 35-37 weeks of gestation. Vaginal secretions and stool were analyzed by 16S rRNA (V3-V4) sequencing using QIIME 2 with SILVA annotation and community state type (CST) classification. Vaginal communities were mainly Lactobacillus-dominant. GBS-Positive women showed a non-significant tendency toward more L. iners-dominant CST III and fewer L. crispatus-dominant CST I compared with GBS-Negative women. Prevotella, Atopobium, and Gardnerella were significantly enriched in the GBS-Positive group (false discovery rate < 0.05), whereas gut microbial diversity and composition showed no significant differences between groups. Cross-site gut-vagina genus-level correlations were generally weak and non-significant. These findings suggest that, in late pregnancy, GBS colonization is linked to subtle shifts within Lactobacillus-dominant vaginal communities, with more L. iners and bacterial vaginosis-associated genera, rather than global microbiota disruption. The apparent shift from L. crispatus- to L. iners-dominant communities is hypothesis-generating and should be confirmed in larger cohorts.