Bacterial vaginosis (BV) is the most common cause of vaginal infection (vaginitis). For grammatical reasons, some people prefer to call it vaginal bacteriosis. It is not generally consiered to be a sexually transmitted infection (see causes below). BV is caused by an imbalance of naturally occurring bacterial flora, and should not be confused with yeast infection (candidiasis), or infection with Trichomonas vaginalis (trichomoniasis) which are not caused by bacteria.