A delicate balance: risk factors for acquisition of bacterial vaginosis include sexual activity, absence of hydrogen peroxide-producing lactobacilli, black race, and positive herpes simplex virus type 2 serology.

BACKGROUND: The etiology of bacterial vaginosis (BV) is poorly understood, but better definition of the risk factors associated with its acquisition should improve our understanding of this complex disease entity.
METHODS: A longitudinal cohort study of young sexually active women was conducted to identify variables associated with BV acquisition. Seven hundred seventy-three women without BV at enrollment were followed at 4-month intervals for 1 year. At each visit, demographic and behavioral interview data, a vaginal smear for the Gram stain diagnosis of BV, and a serum sample for detection of herpes simplex virus type 1 (HSV-1) and HSV-2 type-specific antibodies were collected.
RESULTS: The overall incidence of BV acquisition was 36 cases/100 woman-years (223 acquisitions of BV during 619 woman-years of follow-up). Acquisition of BV was independently associated with black race, cigarette smoking, vaginal intercourse, receptive anal sex before vaginal intercourse, sex with an uncircumcised male partner, lack of vaginal H2O2-producing lactobacilli, and the detection of HSV-2 serum antibodies at the visit before BV acquisition. Longitudinal analyses revealed that HSV-2 serum antibodies were independently associated with loss of H2O2-producing lactobacilli.
CONCLUSIONS: Our findings suggest that multiple and diverse risk factors can contribute to BV acquisition. They also illustrate why a more complete understanding of BV pathogenesis and the formulation of effective BV prevention strategies have been elusive. Further work will be needed to determine the specific effects of HSV-2 infection on vaginal flora composition and the acquisition of BV.