Unveiling the microbial shift: the impact of group B Streptococcus on vaginal microbiota and inflammation in late...

Group B Streptococcus (GBS) commonly colonizes the female reproductive tract and rectum. An estimated 19.7 million pregnant women worldwide are colonized with GBS. Infection during late pregnancy can lead to adverse pregnancy outcomes. Pregnant women infected with GBS face a significantly increased risk of transmitting the bacteria to their newborns during delivery, potentially resulting in serious conditions such as sepsis, pneumonia, and meningitis major contributors to neonatal morbidity and mortality. While previous studies have primarily focused on the prevalence of GBS colonization in pregnant women, its effects on the vaginal microbiota and systemic inflammation remain underexplored. This study aims to investigate the alterations in vaginal microbiota associated with GBS colonization during late pregnancy and to examine correlations between microbiota composition and systemic inflammatory markers in GBS-positive pregnant women.

Pregnant women in late gestation undergoing routine prenatal care were classified into GBS-negative (n = 19) and GBS-positive (n = 20) groups based on their GBS infection status. Vaginal microbiota composition was analyzed using 16 S rRNA gene sequencing to assess the impact of GBS infection. Additionally, the relationship between microbiota profiles and systemic inflammatory markers was evaluated in the GBS-positive group.

GBS-positive women exhibited significant shifts in vaginal microbiota, notably a reduction in Lactobacillus dominance and an increased abundance of pathogenic taxa such as Gardnerella vaginalis and Streptococcus agalactiae. These microbial changes were associated with elevated systemic inflammatory markers, including neutrophil count (NEU), neutrophil percentage (NEU%), high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), procalcitonin (PCT), and erythrocyte sedimentation rate (ESR), suggesting a link between vaginal dysbiosis and systemic inflammation. LEfSe analysis revealed an enrichment of Gemella in GBS-negative women and a predominance of Gardnerella in the GBS-positive group. Correlation analysis showed that Bifidobacterium was positively associated with hs-CRP and IL-6 levels, while Lactobacillus was inversely correlated with hs-CRP, IL-6, and ESR (P < 0.05). Additionally, Dialister and Prevotella were positively associated with ESR (P < 0.05).

GBS colonization disrupts the balance of the vaginal microbiota, contributing to a pro-inflammatory state that may heighten the risk of adverse pregnancy outcomes. In comparison to women who are not colonized by GBS, GBS colonization may be associated with a decrease in the abundance of Lactobacillus jensenii and Lactobacillus reuteri, as well as an increase in Gardnerella vaginalis and Lactobacillus johnsonii. Restoring Lactobacillus (specific microbial species) dominance may help mitigate inflammation and promote maternal and fetal health. Future research should focus on longitudinal monitoring of microbiota dynamics and the development of targeted interventions to prevent or manage GBS-related complications.