An analysis of the vaginal microflora in women positive for Group B Streptococcus during the third trimester of pregnancy

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 infection 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 62 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. 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 16S 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 infection were associated with an increased risk of GBS colonization. Significant differences in the composition of the reproductive microflora were observed across different GBS infection statuses, with notably greater species diversity in the GBS culture-positive group. At the genus level, Lactobacillus was the predominant genus in the GBS culture-positive group, followed by Gardnerella, Streptococcus, and Bifidobacterium. In contrast, in the GBS culture-negative group, Lactobacillus and Gardnerella remained the most abundant genera but were followed by Prevotella, Bacteroides, and others. Furthermore, GBS reproductive tract colonization was positively correlated with the presence of other microorganisms within the microenvironment. Conclusion GBS colonization is positively correlated with the presence of other microorganisms in the reproductive tract microenvironment during late pregnancy. This association may contribute significantly to severe complications, including reproductive tract inflammation, preterm delivery, and premature rupture of membranes in the later stages of pregnancy.