Vaginal Microbiome and Its Relationship to Behavior, Sexual Health, and Sexually Transmitted Diseases

Abstract

The vaginal microbiota has great significance in maintaining vaginal health and protecting the host from disease. Recent advances in molecular techniques and informatics allow researchers to explore microbial composition in detail and to compare the structure of vaginal microbial communities with behavior and health outcomes, particularly acquisition and transmission of sexually transmitted diseases (STDs) and poor birth outcomes. Vaginal flora have been found to cluster into a limited number of communities, although community structure is dynamic. Certain community types are more associated with poor reproductive outcomes and STDs; communities dominated by Lactobacillus species, particularly Lactobacillus crispatus, are most associated with vaginal health. Modifiable and nonmodifiable factors are strongly associated with community composition, including behavior, race or ethnicity, and hygiene. In this review, we describe the state of the science on the vaginal microbiome and its relationship to behavior, sexual health, and STDs, including determinants of the microbiome that go beyond an individual level.

Fig. 1.

Socioecologic framework for determinants of the vaginal micro-biome. Individual and relational determinants associated with differences in the microbiome have been well-studied, and emerging research may show that community-level factors may shape the composition of the microbiome as well. Societal factors that are posited to influence prevalence of sexually transmitted disease (STD) such as segregation, racism, and other societal-level policies may also be determinants of the microbiome. Research that addresses the role of higher level spheres of influence on the microbiome may identify modifiable risk factors that can be addressed. Modified from Scribner R, Theall KP, Simonsen N, Robinson W; National Institute on Alcohol Abuse and Alcoholism. HIV risk and the alcohol environment. Available at: https://pubs.niaaa.nih.gov/publications/arh333/179-183.htm. Retrieved January 4, 2017.

Fig. 2.

Vaginal communities and risk of sexually transmitted diseases (STDs). Risk of STD acquisition and transmission increases with increasing diversity of vaginal flora and is lowest with Lactobacillus crispatus–dominant communities. Higher levels of lactic acid have been strongly associated with vaginal health, and production of lactic acid is conserved across healthy vaginal communities. L- and D-lactic acid isomers may have different functions within the vaginal microenvironment, and their ratio may influence expression of host genes and immune response. CST, community-state types; HIV, human immunodeficiency virus; HSV, herpes simplex virus; HPV, human papillomavirus. *Data from references and . ^†Data from reference and the following: Witkin SS, Mendes-Soares H, Linhares IM, Jayaram A, Ledger WJ, Forney LJ. Influence of vaginal bacteria and D- and L-lactic acid isomers on vaginal extracellular matrix metalloproteinase inducer: implications for protection against upper genital tract infections. MBio 2013 Aug 6;4. pii: e00460–13. DOI: 10.1128/mBio.00460-13.