Abstract
Steroid hormones are one of the presumed modulators of Lactobacillus abundance in the vaginal epithelium. We set out to characterize the vaginal microbiome (VMB) and also provide an in-depth understanding of the relative contribution of estradiol (E2) and progesterone (P1) in shaping the vaginal microbiome of Nigerian women (n = 38) who experienced both uncomplicated term delivery and preterm delivery using samples longitudinally collected during pregnancy (17–21, 27–31, 36–41 weeks gestation) and 6 weeks postpartum. Vaginal swabs and blood samples were aseptically collected. Vaginal swabs were used for microbiome assessment using 16S ribosomal RNA (rRNA) gene sequencing. Blood samples were used for hormonal measurement using a competitive-based enzyme-linked immunosorbent assay (ELISA). Across several maternal covariates, maternal age, pregnancy status and delivery mode were not significantly associated with the vaginal microbiota whereas maternal E2 level (pE2 = 0.006, Omnibus), and P1 level (pP1 = 0.001, Omnibus) were significantly associated with the vaginal microbiome. E2 and P1 concentrations increased throughout pregnancy commensurately with increasing proportions of L. crispatus (pE2 = 0.036, pP1 = 0.034, Linear Mixed Model). An increasing trend of α-diversity was also observed as pregnancy progressed (pobserved ASV = 0.006, LMM). A compositional microbiome shift from Lactobacillus profile to non-Lactobacillus profile was observed in most postnatal women (pCST IV < 0.001, LMM). Analysis of our data shows a species-specific link between pregnancy steroid hormone concentration and L. crispatus abundance.
Highlights
Steroid hormones are one of the presumed modulators of Lactobacillus abundance in the vaginal epithelium
Vaginal microbial communities state types (CSTs) are typically defined by the dominance of one of four Lactobacillus species; L. crispatus (CST I), L. gasseri (CST II), L. iners (CST III) and L. jensenni (CST V) while compositional shift from Atopobium vaginae (CST IV) is defined by heterogenous mixture of strict and facultative a naerobes[8]
Community state types (CST) were assigned to each sample based on amplicon sequence variants (ASVs) abundance using hierarchical clustering with Hellinger distance (Euclidean distance on square-root proportion data) and Ward linkage as described p reviously[46]
Summary
Steroid hormones are one of the presumed modulators of Lactobacillus abundance in the vaginal epithelium. The presence of different Lactobacillus species in the vaginal microenvironment is widely believed to enhance stability of the vaginal microbiome in pregnancy as failure of these species to retain dominance over time (remain stable) may result to overgrowth of anaerobic bacteria including bacterial vaginosis associated bacteria (BVAB1), Prevotella species, Gardnerella vaginalis, Atopobium vaginae, Sneathia, Megasphaera[15] These anaerobes have been shown to be associated with poor pregnancy outcomes such as post-abortal infections, early miscarriage and preterm birth[16,17,18]. This is the first study describing the vaginal microbiota during pregnancy and postpartum longitudinally Using this data, we set out to characterize the VMB during pregnancy and puerperium in Nigerian women and provide an in-depth understanding of the relative contribution of estradiol (E2) and progesterone (P1) in shaping the vaginal microbiome
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