Abstract
Functional equilibrium between vaginal microbiota and the host is important for maintaining gynecological and reproductive health. Apart from host genetics, infections, changes in diet, life-style and hygiene status are known to affect this delicate state of equilibrium. More importantly, the gonadal hormones strongly influence the overall structure and function of vaginal microbiota. Several studies have attempted to understand (a) the composition of vaginal microbiota in specific stages of women’s reproductive cycle as well as in menopause (b) their association with gonadal hormones, and their potential role in manifestation of specific health conditions (from the perspective of cause/consequence). However, a single study that places, in context, the structural variations of the vaginal microbiome across the entire life-span of women’s reproductive cycle and during various stages of menopause is currently lacking. With the objective to obtain a holistic overview of the community dynamics of vaginal micro-environment ‘across’ various stages of women’s reproductive and post-reproductive life-cycle, we have performed a meta-analysis of approximately 1,000 vaginal microbiome samples representing various stages of the reproductive cycle and menopausal states. Objectives of this analysis included (a) understanding temporal changes in vaginal community taxonomic structure and composition as women pass through various reproductive and menopausal stages (b) exploring correlations between the levels of female sex hormones with vaginal microbiome diversity (c) analyzing changes in the pattern of community diversity in cases of dysbiotic conditions such as bacterial vaginosis, and viewing the analyzed changes in the context of a healthy state. Results reveal interesting temporal trends with respect to vaginal microbial community diversity and its pattern of correlation with host physiology. Results indicate significant differences in alpha-diversity and overall vaginal microbial community members in various reproductive and post-reproductive phases. In addition to reinforcing the known influence/role of gonadal hormones in maintaining gynecological health, results indicate how hormonal level perturbations cause/contribute to imbalances in vaginal microbiota. The nature of resulting dysbiotic state and its influence on vaginal health is also analyzed and discussed. Results also suggest that elevated vaginal microbial diversity in pregnancy does not necessarily indicate a state of bacterial infection. The study puts forward a hormone-level driven microbiome diversity hypothesis for explaining temporal patterns in vaginal microbial diversity during various stages of women’s reproductive cycle and at menopause.
Highlights
The human microbiota comprises of trillions of micro-organisms inhabiting different body sites and is involved in diverse functions (Grice and Segre, 2012; Wang et al, 2017)
Given the intention to study ‘native’ vaginal microbial community structure and taxonomic composition, the data corpus was built using the specific subset of samples from women who were agnostic to any exogenous medical interventions that are known to impact the structure of vaginal microbiome (Farage et al, 2017; Achilles et al, 2018)
It is pertinent to note that the vaginal microbiota samples tagged as ‘BV-Negative’ are a subset of the samples from an earlier study (Ravel et al, 2011) which were collected from ‘reproductive-aged’ women who were not pregnant, regularly menstruating, had refrained from usage of any antibiotic or/and contraceptive drugs and were not suffering with bacterial vaginosis
Summary
The human microbiota comprises of trillions of micro-organisms inhabiting different body sites and is involved in diverse functions (Grice and Segre, 2012; Wang et al, 2017). Through their intricate involvement in various aspects of host physiology and metabolism, microbiota assist the host in key functions such as nutrient absorption, maturation of immune system, defending host from pathogens, etc. Apart from this, fluctuations in hormonal levels across various stages of women’s reproductive cycle and during menopausal states bring about considerable changes in the vaginal microbial ecosystem (Vitali et al, 2017). Other substances produced by lactobacilli in the vaginal micro-environment such as hydrogen peroxide and bacteriocins inhibit the growth of potential pathogens (Jack et al, 1995; Hawes et al, 1996; Dover et al, 2008)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
