Impact of bacterial vaginosis on sexually transmitted viral infections: a bacterial point of view.

Bacterial vaginosis (BV) is a complex polymicrobial vaginal infection that affects a large percentage of women during different stages of life including the reproductive age. In a healthy vaginal environment, the epithelium is colonized by protective Lactobacillus species that make up 90%-95% of the total vaginal microbiota. BV is characterized by a reduction of lactobacilli and a concurrent increase in diverse anaerobic bacteria, including Gardnerella vaginalis, Prevotella bivia, Hoylesella timonensis, and Fannyhessea vaginae. BV is associated with an increased risk of infertility, preterm birth, and a higher susceptibility to sexually transmitted infections (STIs), including Human Immunodeficiency Virus type-1 (HIV-1). This review examines the contribution of individual pathogenic bacteria to the development of BV and the resulting effects on susceptibility to STI. The impact of the different key bacterial virulence factors, such as secreted proteins, biofilm formation, and inflammatory potential on subsequent viral infection are discussed. While antibiotics are commonly prescribed to treat BV, recurrence rates are high, and antimicrobial resistance among BV-associated bacteria is increasingly reported. Understanding the mechanisms underlying BV and the impact of specific bacteria and their virulence factors on viral infections can improve preventive strategies and open up novel therapeutic applications.