• The outcome of incident STDs (chlamydial and gonococcal infections) determined by vaginal swab testing. [ Time Frame: 4, 8, and 12 months after enrollment ] [ Designated as safety issue: No ]
  

• Change in BV status. [ Time Frame: Over 12 months ] [ Designated as safety issue: No ]
  

Bacterial vaginosis (BV) is characterized by an imbalance in the normal vaginal bacterial flora. In the United States, BV is very common, and the most common cause of vaginitis, affecting approximately 1 in 10 sexually active young women. Because BV is so common, interventions targeting BV could have a tremendous public health impact. This is a phase III randomized controlled trial, in which the primary objective is to determine whether regular screening (every two months) and treatment for asymptomatic BV can reduce the one-year incidence of chlamydial and gonococcal infections, compared to a control group of women who receive regular monitoring (every two months) for BV but no treatment. The secondary study objective is to determine demographic and behavioral factors associated with the acquisition of BV, its persistence among women who are not treated for this condition, its spontaneous resolution, and its recurrence in women who are treated for this condition. This trial will recruit 1,800 women, ages 15 - 25 years, from 6 sites within the Sexually Transmitted Infections Clinical Trials Group (STI CTG) network. To be eligible, women must have 2 or more risk factors for sexually transmitted diseases (STDs) and must have clinical evidence of asymptomatic BV at enrollment. For the purposes of this study, asymptomatic BV is defined by the presence of a pH greater than 4.5, the presence clue cells (greater than 20%), and the absence of subject reported unusual/abnormal vaginal odor or discharge. After informed consent is obtained, eligible women will be randomized to either an intervention group (screening and treatment for asymptomatic BV) or a control group (monitoring for BV without treatment). All subjects will receive bi-monthly (every two months) home self-testing kits for BV using a vaginal swab. If BV is detected by self-test, the subjects in the interventional group will receive metronidazole 500mg twice daily for 7 days. Subjects in both the intervention group and the control group will complete bi-monthly (every 2 months) follow-up assessments for BV at months 2, 4, 6, 8, 10, and 12 (the final follow-up). In addition, subjects will provide sample collections for Chlamydia trachomatis and Neisseria gonorrhoeae at 4, 8, and 12 months after study entry. The primary study outcome is incident chlamydial and gonococcal infections detected during one year of follow-up. For this outcome, researchers will consider two measures: cumulative STD incidence rate at one year and the cumulative proportion of participants who acquire at least one chlamydial or gonococcal infection by one year. The secondary study outcome is BV at any assessment point, as defined by microbiologic assessment of a gram-stained vaginal swab specimen.