Gardnerella vaginalis is a type of bacteria that is normally present in the vagina as part of the vaginal flora. When the levels of Gardnerella are in balance with the other bacteria, the vaginal flora prevents infections. However, if there is an imbalance and too much Gardnerella grows, it can cause a vaginal infection called bacterial vaginosis (BV) . BV is the most common cause of vaginal discharge and can cause discomfort and pain in the vagina. The exact causes of BV are unknown, but it is believed that anything that changes the chemistry of the vaginas pH balance can mess with bacteria levels and lead to infection, such as douching, using vaginal deodorants, and other irritating products. BV is not considered a sexually transmitted infection (STI), but having sex with a new partner or multiple partners may increase the risk of developing BV. Gardnerella vaginalis is not an STI-causing bacteria, but it is most likely transmitted sexually.