The Female Vaginal Microbiome in Health and Bacterial Vaginosis

Abstract

The vaginal microbiome is an intricate and dynamic microecosystem that constantly undergoes fluctuations during the female menstrual cycle and the woman's entire life. A healthy vaginal microbiome is dominated by Lactobacillus which produce various antimicrobial compounds. Bacterial vaginosis (BV) is characterized by the loss or sharp decline in the total number of Lactobacillus and a corresponding marked increase in the concentration of anaerobic microbes. BV is a highly prevalent disorder of the vaginal microbiota among women of reproductive age globally. BV is confirmed to be associated with adverse gynecologic and obstetric outcomes, such as sexually transmitted infections, pelvic inflammatory disease, and preterm birth. Gardnerella vaginalis is the most common microorganism identified from BV. It is the predominant microbe in polymicrobial biofilms that could shelter G. vaginalis and other BV-associated microbes from adverse host environments. Many efforts have been made to increase our understanding of the vaginal microbiome in health and BV. Thus, improved novel and accurate diagnosis and therapeutic strategies for BV have been developed. This review covers the features of vaginal microbiome, BV, BV-associated diseases, and various strategies of diagnosis and treatment of BV, with an emphasis on recent research progresses.

Keywords: Gardnerella vaginalis; Lactobacillus; bacterial vaginosis; female health; vaginal microbiome.

Figure 1

Characteristics of BV (A, C) and normal (B, D) vaginal microbiome. (A, C) show the colposcopic and microscopic examination of BV vaginal discharges, respectively. Homogeneous and milk-like secretions, Gardnerella-like microbes, and clue cells are observed. (B, D) show the colposcopic and microscopic examinations of normal vaginal discharges, respectively. Homogeneous and clear secretions, Lactobacillus-like microbes, and no clue cells are observed.

Figure 2

Diagram of the impact of different therapeutic regimens on vaginal microbiome. (A) BV vaginal microbiome before treatment. This vaginal microbiome refers to high diversity of microbial community dominated by anaerobic bacteria instead of Lactobacillus. Meanwhile, the polymicrobial biofilms are formed on vaginal epithelium. (B) Treatment with antibiotics alone reduces the microbial diversity and causes the recovery of Lactobacillus population, but the biofilms have not been disrupted. (C) Treatment with antibiotics and adjuvant reduces the microbial diversity and causes the recovery of Lactobacillus population; moreover, the biofilms have been disrupted.