EVIDENCE-BASED ANSWER
The best way to prevent recurrent bacterial vaginosis is to treat the initial episode with the most effective regimen. Metronidazole (500 mg orally twice daily for 7 days) has the lowest recurrence rate among antimicrobial regimens for bacterial vaginosis (20% vs 34%–50% for other agents) (strength of recommendation [SOR]: A). Women should be treated if they are symptomatic (SOR: A), undergoing gynecologic surgery (SOR: B), or at risk for preterm labor (SOR: B).
When bacterial vaginosis recurs, providers should confirm the diagnosis (Table 1) (SOR: A), identify and control risk factors for recurrence ( Table 2) (SOR: B), and consider other causes while retreating bacterial vaginosis (SOR: C). If the diagnosis is confirmed and retreatment fails, consider suppression with metronidazole 0.75% vaginal gel for 10 days followed by twice weekly administration for 4 to 6 months (SOR: C, trial ongoing). No evidence supports treating sexual partners or administering oral or vaginal Lactobacillus acidophilus, but recolonization with vagina-specific lactobacilli (L crispatus and L jensenii) is undergoing Phase III clinical trials.
Evidence summary
No trials have tested or compared specific, comprehensive strategies for recurrent bacterial vaginosis. Given that bacterial vaginosis can also be asymptomatic, recurrence often cannot be differentiated from treatment failure. Accordingly, recurrent bacterial vaginosis may be prevented by using the most effective therapy for the initial episode. A 2002 meta-analysis by the Centers for Disease Control and Prevention’s (CDC) bacterial vaginosis working group reviewed the indications for therapy and best treatments for bacterial vaginosis.1 The group found 25 trials evaluating oral metronidazole therapy involving 2742 women. Although cure rates using either 500 mg twice daily for 5 to 7 days or 2 g as a single dose were similar at 2 weeks post follow-up (85%; range 67%–98%), the single-dose regimen led to higher relapse rates 1 month after treatment (35%–50% vs 20%–33%).
Six trials enrolling 946 women assessed the efficacy of various topical vaginal treatments. Metronidazole gel, clindamycin cream, and clindamycin ovules had a wide range of initial cure rates (50%–95%), but all had higher relapse rates at 4 weeks than did oral metronidazole for 1 week (34%–49%).1 A more complete discussion of the effectiveness of antibiotics for bacterial vaginosis can be found in a recent Clinical Inquiry.2
The CDC reviewers identified causal relationships between bacterial vaginosis and plasmacell endometritis, postpartum fever, and posthysterectomy vaginal-cuff cellulitis. They therefore concluded it is reasonable to try to prevent post-procedure infections by treating women who have asymptomatic bacterial vaginosis before hysterectomy or pregnancy termination. Although bacterial vaginosis has been associated with preterm labor, trials evaluating treatment of bacterial vaginosis to prevent preterm delivery are conflicting. A Cochrane review of bacterial vaginosis and preterm labor suggests treating women at high risk for preterm birth may reduce the risk of low birthweight and preterm prelabor rupture of membranes.3
Patients frequently try to self-diagnose vaginal complaints and ask for treatments and retreatments by phone. However, a prospective study of 253 women who underwent a structured telephone interview and subsequent physical exam found a poor correlation between telephone diagnosis and final clinical diagnosis (kappa coefficient of 0.12—very poor agreement).4 Accordingly, clinical and laboratory evaluation of vaginal discharge and especially recurrent symptoms is essential for diagnostic accuracy and treatment for bacterial vaginosis (Table 1).
For recurrent symptomatic bacterial vaginosis, 1 option is suppressive therapy with metronidazole gel 0.75%. After initial daily retreatment for 10 days, this can be used twice weekly for 4 to 6 months to decrease symptoms. This strategy is based on expert opinion but is currently undergoing clinical trial.
One small crossover randomized controlled trial of 46 women with bacterial vaginosis studied the consumption of live L acidophilus cultures.5 Only 20 of the women had recurrent bacterial vaginosis. The groups were randomized to eat yogurt with and without live L acidophilus cultures. While the results were encouraging (50% reduction in episodes of bacterial vaginosis and increase in detectable vaginal Lactobacillus), only 7 women actually completed the study protocol.