Associations between sexual habits, menstrual hygiene practices, demographics and the vaginal microbiome as revealed by Bayesian network analysis

Abstract

The vaginal microbiome plays an influential role in several disease states in reproductive age women, including bacterial vaginosis (BV). While demographic characteristics are associated with differences in vaginal microbiome community structure, little is known about the influence of sexual and hygiene habits. Furthermore, associations between the vaginal microbiome and risk symptoms of bacterial vaginosis have not been fully elucidated. Using Bayesian network (BN) analysis of 16S rRNA gene sequence results, demographic and extensive questionnaire data, we describe both novel and previously documented associations between habits of women and their vaginal microbiome. The BN analysis approach shows promise in uncovering complex associations between disparate data types. Our findings based on this approach support published associations between specific microbiome members (e.g., Eggerthella, Gardnerella, Dialister, Sneathia and Ruminococcaceae), the Nugent score (a BV diagnostic) and vaginal pH (a risk symptom of BV). Additionally, we found that several microbiome members were directly connected to other risk symptoms of BV (such as vaginal discharge, odor, itch, irritation, and yeast infection) including L. jensenii, Corynebacteria, and Proteobacteria. No direct connections were found between the Nugent Score and risk symptoms of BV other than pH, indicating that the Nugent Score may not be the most useful criteria for assessment of clinical BV. We also found that demographics (i.e., age, ethnicity, previous pregnancy) were associated with the presence/absence of specific vaginal microbes. The resulting BN revealed several as-yet undocumented associations between birth control usage, menstrual hygiene practices and specific microbiome members. Many of these complex relationships were not identified using common analytical methods, i.e., ordination and PERMANOVA. While these associations require confirmatory follow-up study, our findings strongly suggest that future studies of the vaginal microbiome and vaginal pathologies should include detailed surveys of participants’ sanitary, sexual and birth control habits, as these can act as confounders in the relationship between the microbiome and disease. Although the BN approach is powerful in revealing complex associations within multidimensional datasets, the need in some cases to discretize the data for use in BN analysis can result in loss of information. Future research is required to alleviate such limitations in constructing BN networks. Large sample sizes are also required in order to allow for the incorporation of a large number of variables (nodes) into the BN, particularly when studying associations between metadata and the microbiome. We believe that this approach is of great value, complementing other methods, to further our understanding of complex associations characteristic of microbiome research.

The genital tract and rectal microbiomes: their role in HIV susceptibility and prevention in women

“…In addition, several environmental factors such as hormonal contraceptives; sexual activity (including the number of partners and semen, as well as lubricants), hygiene practices, antibiotics and the composition of the gastrointestinal microbiota (transferred from the nearby rectum) can all influence the composition of the female genital tract microbiome , although it should be noted these data are not entirely consistent.…”

The Interplay Between Reproductive Tract Microbiota and Immunological System in Human Reproduction

“…In non-pregnant women of reproductive age, transient variations in the vaginal microbiota's dynamic equilibrium are the results of physiological changes in response to hormones during the menstrual cycle, or human activities (e.g., sexual intercourse and hygienic practices) (18). In addition, other constitutional and environmental factors, including age, ethnicity, geographical variation and sexual habits influence the bacterial communities detected in the lower urogenital tract (19)(20)(21). For example, Lactobacilli-dominated vaginal microbiota has been shown to be less prevalent among non-Caucasian women in several studies (22)(23)(24), though, when present, their beneficial role seems maintained.…”

“…A well-known study performed in North America characterized the vaginal microbiota of women of reproductive age from four ethnic groups (Caucasian, African-American, Hispanic and Asian): five groups of microbial communities, called Community State Types (CSTs) were identified. Whereas CST-IV was the most diverse CST and was also associated with a higher local pH, the remaining four (CST-I, CST-II, CST-III, and CST-V) were dominated by Lactobacilli (20). Lactobacilli thrive in anaerobic environments and produce lactic acid, therefore contributing to the acidic vaginal environment.…”

Determinants of Vaginal Microbiota Composition

“…Probabilistic models offer a method to infer causal relationships from complex and disparate datasets. Noyes et al used Bayesian Networks to explore the associations between sexual and hygiene behaviors and VMB composition (Noyes et al, 2018 ). They identified both novel and known relationships; including L. iners with older age, Ureaplasma with previous pap smear, and L. crispatus with any contraceptive use.…”