Review articleMenopause and the vaginal microbiome
Introduction
Researchers have been investigating bacteria that inhabit the vaginal cavity since the 1800s. Early scientists used light microscopy and Gram staining to study the microbial composition of the vaginal environment. As technology progressed, bacterial culturing techniques and PCR were developed and researchers were able to more accurately identify bacterial species that are present in the vagina. Currently, 16S rRNA sequencing provides a culture-independent method to identify the vaginal microbiota [1]. Next-generation sequencing can be used effectively to characterize a large array of taxonomic species that would not be possible with other methods
An environment rich in Lactobacillus species is associated with vaginal health [2]. Although other anaerobic and aerobic bacteria colonize the vagina, Lactobacillus is the dominant species in most women [1], [2]. Lactobacillus spp. produce compounds such as hydrogen peroxide and lactic acid that have antimicrobial properties [3]. The resulting microenvironment is critically important in preventing colonization of the vagina by diverse, anaerobic and microaerophilic pathogens, which can result in depletion of lactobacilli and dysbiosis (imbalance of vaginal community) called bacterial vaginosis (BV) [4]. BV has been associated with an array of poor obstetric and gynecologic health outcomes in both pre- and postmenopausal women [1], [4], [5], [6]. Particularly relevant to postmenopausal women, disruptions in the vaginal microbiota affect vulnerability to gynecologic infections and sexually transmitted infections (STI) [4], [7], [8], [9].
Multiple studies have focused on the vaginal microbiota in healthy, reproductive-aged women and recent sequence-based studies have begun to elucidate the dominant vaginal community states in menopausal women (Table 1). A plethora of changes take place during menopause that affect both the microanatomical structure and microbiome of the lower female reproductive tract [10]. Local, vaginal symptoms include vaginal dryness, vaginal atrophy, and dyspareunia can negatively impact a woman’s quality of life [10].
The objective of this review it to compare the changes that have been identified in the vaginal microbiome of menopausal women, outline alterations in the microbiome associated with specific menopausal symptoms, define how hormone replacement therapy impacts the vaginal microbiome and menopausal symptoms and sexual health and quality of life, and conclude with the potential of probiotics to reinstate vaginal homeostasis following menopause.
Section snippets
Methods
A search of the scientific literature was conducted using PubMed/Medline using the following search terms “vaginal microbiota and menopause”, “vaginal microbiome and menopause”, “vaginal flora and menopause”, “vaginal bacteria and menopause”, “vaginal atrophy and menopause”, and “vulvovaginal atrophy and the vaginal microbiota”. Pertinent original articles and reviews that were peer-reviewed, indexed in PubMed/Medline and written in English were included. The publication dates were not limited
Characterization of the vaginal microbiome in menopause
Early studies investigating the bacterial composition of the vagina used cytology and Gram staining techniques. Coupled with the use of bacterial culture techniques, researchers found that vaginal lactobacilli, yeasts and BV were less common in postmenopausal women compared to premenopausal women [11], [12], [13]. In postmenopausal women on hormone replacement therapy (HRT), there was a strong association with the level of Lactobacillus colonization [12], [13]. According to Cauci et al., 44.1%
Conclusions
Research regarding the vaginal microbiome and menopause has evolved over the last decade. Light microscopy and culture techniques revealed healthy vaginal microbiomes are dominated by Lactobacillus species. Next- generation sequencing technology has allowed scientists to further categorize and understand the complexity and diversity of species that inhabit the vaginal cavity. Overall, Lactobacillus dominance is strongly correlated to vaginal health and homeostasis in both pre- and
Contributors
MMH-K designed the scope and organization of the review.
ALM and MMH-K conducted literature reviews, data extraction and analysis, figure and table construction and contributed to the writing of the manuscript.
MMH-K supervised the writing and critically edited and reviewed the complete manuscript, table and figure.
Both authors approved the final manuscript for submission.
Conflict of interest
The authors declare no conflict of interest.
Funding
This work was supported by the University of Arizona.
Provenance and peer review
This article has undergone peer review.
Acknowledgement
The authors would like to thank the members of the Herbst-Kralovetz research team for thoughtful discussions on this topic.
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