An analysis of the vaginal microbiota in women positive for group B Streptococcus during the third trimester of pregnancy

Abstract

Background

Presently, 20–40% of pregnant women are colonized with Streptococcus agalactiae, which is commonly referred to as Group B Streptococcus (GBS). Numerous studies have demonstrated the association of GBS colonization with adverse pregnancy outcomes and neonatal infectious diseases. However, few studies have explored the complex interactions between GBS and other reproductive tract microbes.

Method

This study employed a retrospective case‒control design. The research subjects included 53 pregnant women at 35–37 weeks of gestation who received treatment at Shenyang Women and Infants Hospital between November 1, 2022, and July 1, 2024 (GBS culture-positive group vs. GBS culture-negative group: 22 vs. 31). Chi-square tests and multiple logistic regression analyses were performed to identify factors associated with genital tract colonization in GBS patients. Additionally, reproductive tract swabs from 53 pregnant women were subjected to 16 S rRNA microbiome analysis using the Illumina NovaSeq platform.

Results

Our analysis revealed that factors such as premature rupture of membranes, preterm delivery, diabetes mellitus, vaginal cleanliness, elevated leukocyte count in the vaginal discharge, and fungal colonization were associated with GBS colonization. The presence of both shared and unique amplicon sequence variants (ASVs) was observed between the GBS culture-negative and GBS culture-positive groups. The beta diversity values revealed significant differences in species composition between the groups. The GBS culture-positive group presented greater species richness, reduced homogeneity, and a notable reduction in the abundance of Lactobacillus.

Conclusion

GBS shares intricate relationships with other bacterial taxa within the reproductive tract. Understanding and optimizing the composition and dynamics of the reproductive tract microbiota can provide theoretical support and guidance for clinical prevention and treatment of GBS colonization, thereby reducing adverse pregnancy outcomes and neonatal infectious diseases in patients with GBS colonization.