New insights into Gardnerella and other BV-associated bacteria

[Excerpt] Bacterial vaginosis (BV), the most common vaginal disorder in women of reproductive age, remains one of the most intriguing and controversial challenges in modern-day clinical microbiology. BV is associated with increased transmission of HIV and other STIs, and is characterized by the loss of normal vaginal flora and overgrowth of anaerobes such as Gardnerella. However, it is not clear which is the preceding step for BV development: the loss of resident lactobacilli that eventually allows the overgrowth of already resident Gardnerella species, or the colonization of Gardnerella, presumably acquired due to sexual transmission, which will lead to the displacement of vaginal lactobacilli. However, Gardnerella colonization does not always lead to BV. Importantly, a recent large genome sequencing study demonstrated that what was previously described as G. vaginalis are, in fact, distinct species of the genus Gardnerella. It has been hypothesized that the distinct Gardnerella species have different virulence potential and that this can explain why some Gardnerella are present in healthy women without developing BV. [...]