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

Study information

Reviewed Marked as Reviewed by KateRasheed on 2025-10-9

study design

case-control

Citation

PMID PubMed identifier for scientific articles.

40713506

DOI Digital object identifier for electronic documents.

10.1186/s12866-025-04184-0

URI Uniform resource identifier for web resources.

Authors

Zhang T, Tong C, Wang J, Gao S, Li K, Wang X

Journal

BMC microbiology

Year

2025

Keywords:

Group B Streptococcus, Pregnant, Vagina, Vaginal microbiota

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.

Experiment 1

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Reviewed Marked as Reviewed by KateRasheed on 2025-10-9

Curated date: 2025/10/07

Curator: Tosin

Revision editor(s): Tosin

Subjects

Location of subjects: China

Host species Species from which microbiome was sampled. Contact us to have more species added.: Homo sapiens

Body site Anatomical site where microbial samples were extracted from according to the Uber Anatomy Ontology: Vagina Distal oviductal region,Distal portion of oviduct,Vaginae,Vagina,vagina

Condition The experimental condition / phenotype studied according to the Experimental Factor Ontology: Streptococcal infection infection, streptococcal,infections, streptococcal,streptococcal infection,Streptococcal Infections,Streptococcus caused disease or disorder,Streptococcus disease or disorder,Streptococcus infectious disease,Streptococcal infection

Group 0 name Corresponds to the control (unexposed) group for case-control studies: GBSneg (group B Streptococcus culture-negative) pregnant women

Group 1 name Corresponds to the case (exposed) group for case-control studies: GBSpos (group B Streptococcus culture-positive) pregnant women

Group 1 definition Diagnostic criteria applied to define the specific condition / phenotype represented in the case (exposed) group: Pregnant women who tested positive for GBS (group B Streptococcus) by culture during the third trimester

Group 0 sample size Number of subjects in the control (unexposed) group: 31

Group 1 sample size Number of subjects in the case (exposed) group: 22

Lab analysis

Sequencing type: 16S

16S variable region One or more hypervariable region(s) of the bacterial 16S gene: V3-V4

Sequencing platform Manufacturer and experimental platform used for quantifying microbial abundance: Illumina

Statistical Analysis

Data transformation Data transformation applied to microbial abundance measurements prior to differential abundance testing (if any).: relative abundances

Statistical test: LEfSe

Significance threshold p-value or FDR threshold used for differential abundance testing (if any): 0.05

MHT correction Have statistical tests be corrected for multiple hypothesis testing (MHT)?: No

LDA Score above Threshold for the linear discriminant analysis (LDA) score for studies using the popular LEfSe tool: 4

Matched on Factors on which subjects have been matched on in a case-control study: gestational age, parity

Alpha Diversity

Shannon Estimator of species richness and species evenness: more weight on species richness: unchanged

Chao1 Abundance-based estimator of species richness: unchanged

Simpson Estimator of species richness and species evenness: more weight on species evenness: unchanged

Richness Number of species: unchanged

Faith Phylogenetic diversity, takes into account phylogenetic distance of all taxa identified in a sample: unchanged

Signature 1

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Reviewed Marked as Reviewed by KateRasheed on 2025-10-9

Curated date: 2025/10/07

Curator: Tosin

Revision editor(s): Tosin

Source: Figure 6

Description: Linear discriminant analysis (LDA) effect size (LEfSe) biomarker analysis showing taxa with significant differential abundance in GBS (group B streptococcus) culture-negative versus GBS (group B streptococcus) culture-positive pregnant women

Abundance in Group 1: increased abundance in GBSpos (group B Streptococcus culture-positive) pregnant women

NCBI	Quality Control	Links
Acidimicrobiia
Actinomycetota
Bifidobacteriaceae
Bifidobacteriales
Streptococcaceae
Streptococcus
Streptococcus agalactiae

Revision editor(s): Tosin

Signature 2

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Reviewed Marked as Reviewed by KateRasheed on 2025-10-9

Curated date: 2025/10/07

Curator: Tosin

Revision editor(s): Tosin

Source: Figure 6

Description: Linear discriminant analysis (LDA) effect size (LEfSe) biomarker analysis showing taxa with significant differential abundance in GBS (group B streptococcus) culture-negative versus GBS (group B streptococcus) culture-positive pregnant women

Abundance in Group 1: decreased abundance in GBSpos (group B Streptococcus culture-positive) pregnant women

NCBI	Quality Control	Links
Bacilli
Bacillota
Lactobacillaceae
Lactobacillales
Lactobacillus
Lactobacillus crispatus
Lactobacillus iners

Revision editor(s): Tosin