Alterations of the vaginal microbiome in healthy pregnant women positive for group B Streptococcus colonization during the third trimester

AbstractBackgroundStreptococcus agalactiaeor group B Streptococcus (GBS) asymptomatically colonizes the genitourinary tracts of up to 30% of pregnant women. Globally, GBS is an important cause of neonatal morbidity and mortality. GBS has recently been linked to adverse pregnancy outcomes. The potential interactions between GBS and the vaginal microbiome composition remain poorly understood. In addition, little is known about the vaginal microbiota of pregnant Egyptian women.ResultsUsing V3-V4 16S rRNA next-generation sequencing, we examined the vaginal microbiome in GBS culture-positive pregnant women (22) and GBS culture-negative pregnant women (22) during the third trimester in Ismailia, Egypt. According to the alpha-diversity indices, the vaginal microbiome of pregnant GBS culture-positive women was significantly more diverse and less homogenous. The composition of the vaginal microbiome differed significantly based on beta-diversity between GBS culture-positive and culture-negative women. The phylumFirmicutesand the familyLactobacillaceaewere significantly more abundant in GBS-negative colonizers. In contrast, the phylaActinobacteria,Tenericutes, andProteobacteriaand the familiesBifidobacteriaceae,Mycoplasmataceae,Streptococcaceae,Corynebacteriaceae,Staphylococcaceae, andPeptostreptococcaceaewere significantly more abundant in GBS culture-positive colonizers. On the genus and species levels,Lactobacilluswas the only genus detected with significantly higher relative abundance in GBS culture-negative status (88%), andL. inerswas the significantly most abundant species. Conversely, GBS-positive carriers exhibited a significant decrease inLactobacillusabundance (56%). In GBS-positive colonizers, the relative abundance of the generaUreaplasma,Gardnerella,Streptococcus,Corynebacterium,Staphylococcus, andPeptostreptococcusand the speciesPeptostreptococcus anaerobiuswas significantly higher. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to the metabolism of cofactors and vitamins, phosphatidylinositol signaling system, peroxisome, host immune system pathways, and host endocrine system were exclusively enriched among GBS culture-positive microbial communities. However, lipid metabolism KEGG pathways, nucleotide metabolism, xenobiotics biodegradation and metabolism, genetic information processing pathways associated with translation, replication, and repair, and human diseases (Staphylococcus aureusinfection) were exclusively enriched in GBS culture-negative communities.ConclusionsUnderstanding how perturbations of the vaginal microbiome contribute to pregnancy complications may result in the development of alternative, targeted prevention strategies to prevent maternal GBS colonization. We hypothesized associations between inferred microbial function and GBS status that would need to be confirmed in larger cohorts.