The Complex Link between the Female Genital Microbiota, Genital Infections, and Inflammation

Abstract

The female genital tract microbiota is part of a complex ecosystem influenced by several physiological, genetic, and behavioral factors. It is uniquely linked to a woman's mucosal immunity and plays a critical role in the regulation of genital inflammation. A vaginal microbiota characterized by a high abundance of lactobacilli and low overall bacterial diversity is associated with lower inflammation. On the other hand, a more diverse microbiota is linked to high mucosal inflammation levels, a compromised genital epithelial barrier, and an increased risk of sexually transmitted infections and other conditions. Several bacterial taxa such as Gardnerella spp., Prevotella spp., Sneathia spp., and Atopobium spp. are well known to have adverse effects; however, the definitive cause of this microbial dysbiosis is yet to be fully elucidated. The aim of this review is to discuss the multiple ways in which the microbiota influences the overall genital inflammatory milieu and to explore the causes and consequences of this inflammatory response. While there is abundant evidence linking a diverse genital microbiota to elevated inflammation, understanding the risk factors and mechanisms through which it affects genital health is essential. A robust appreciation of these factors is important for identifying effective prevention and treatment strategies.

Keywords: cytokines; female genital tract; immune response; inflammation; vaginal microbiota.

FIG 1

Common causes and consequences of a diverse, inflammatory genital microbiota. The shift to a more diverse genital microbiota is characterized by a marked decline in the abundance of Lactobacillus spp. and lower concentrations of glycogen and antimicrobial peptides, including lactic acid. This is accompanied by high levels of proinflammatory cytokines and chemokines and epithelial barrier damage. Several factors can potentially influence this transition to a higher inflammatory state, including sexual/reproductive practices, the use of antibiotics or probiotics, the vaginal virome, genetics, and lifestyle-related factors such as the woman’s diet, stress, or smoking. This in turn leads to an increase in the risk of subsequent STI acquisition, vulvovaginal candidiasis infection, or preterm birth in some women.