What is the recommended treatment for bacterial vaginosis, including first‑line therapy, alternative regimens, safety in pregnancy, need for partner treatment, and management of recurrence?

Treatment of Bacterial Vaginosis

First-Line Treatment for Symptomatic Non-Pregnant Women

For symptomatic bacterial vaginosis in non-pregnant women, use metronidazole 500 mg orally twice daily for 7 days, which achieves cure rates of 78-84%. 1

Alternative first-line regimens with comparable efficacy include:

• Metronidazole gel 0.75%, one full applicator (5g) intravaginally twice daily for 5 days (78-84% cure rate, with <2% systemic absorption compared to oral dosing) 1
• Clindamycin 2% vaginal cream, one full applicator (5g) intravaginally at bedtime for 7 days 1

Alternative Regimens (Lower Efficacy)

When first-line options are not feasible:

• Metronidazole 2g orally as a single dose (lower efficacy at 84% compared to 7-day regimen; should not be used as first-line) 2, 1
• Clindamycin 300 mg orally twice daily for 7 days 1
• Tinidazole 2g once daily for 2 days or 1g once daily for 5 days (therapeutic cure rates of 22-32% when defined by strict criteria requiring resolution of all 4 Amsel criteria plus Nugent score <4) 3

Critical Patient Instructions

Patients taking metronidazole must avoid all alcohol during treatment and for 24 hours after completion to prevent disulfiram-like reactions. 1

Clindamycin cream is oil-based and weakens latex condoms and diaphragms for the entire 7-day treatment course, making barrier contraception unreliable. 1

Treatment During Pregnancy

Symptomatic Pregnant Women

All symptomatic pregnant women require treatment regardless of risk status, because BV is associated with premature rupture of membranes, preterm labor, preterm birth, and postpartum endometritis. 1

For symptomatic pregnant women, use metronidazole 250 mg orally three times daily for 7 days (lower-dose regimen to limit fetal exposure while maintaining efficacy). 4, 1

Avoid clindamycin 2% vaginal cream in pregnancy because randomized trials show increased risk of preterm delivery with this agent. 1

Pregnant women require follow-up evaluation one month after treatment completion to verify cure and reduce risk of pregnancy complications. 1

Asymptomatic Pregnant Women

Screen and treat high-risk pregnant women (those with prior preterm delivery) who have asymptomatic BV during the early second trimester, as early treatment may reduce adverse pregnancy outcomes. 5, 1

Do not routinely screen or treat average-risk pregnant women with asymptomatic BV, as it does not improve outcomes such as preterm labor or preterm birth. 5

Treatment Before Procedures

Treat asymptomatic BV before surgical abortion procedures to reduce post-abortion pelvic inflammatory disease. 5, 1

Consider treatment before hysterectomy and other invasive gynecological procedures due to increased risk of postoperative infectious complications, including endometritis, PID, and vaginal cuff cellulitis. 5

Partner Treatment

Do not routinely treat male sexual partners, as multiple clinical trials demonstrate that partner treatment does not alter the woman's clinical response, relapse rate, or recurrence rate. 1, 4

Management of Recurrent Bacterial Vaginosis

For recurrent BV (recurrence within 12 months, which occurs in 50-80% of women), use metronidazole 500 mg orally twice daily for 10-14 days. 6, 7

If the extended oral course is ineffective, use metronidazole gel 0.75% intravaginally for 10 days, followed by twice weekly maintenance for 3-6 months. 6

The high recurrence rate may be due to:

• Biofilm formation that protects BV-causing bacteria from antimicrobial therapy 6, 7
• Failure of beneficial Lactobacillus crispatus to recolonize the vagina after antibiotic treatment 8
• Possible reinfection from male or female partners 6

Follow-Up

No routine follow-up visits are necessary if symptoms resolve in non-pregnant women, but patients should return if symptoms persist or recur. 1

Pregnant women are the exception and require follow-up one month after treatment to verify cure. 1

Common Diagnostic and Treatment Pitfalls

Do not culture for Gardnerella vaginalis, as this organism can be isolated from 50% of normal women and is not specific for BV. 1

Diagnose BV using clinical criteria (3 of 4 Amsel criteria) or Gram stain with Nugent scoring, not culture. 2

The four Amsel criteria are:

• Homogeneous white noninflammatory discharge coating vaginal walls 2
• Clue cells on microscopic examination 2
• Vaginal pH >4.5 2
• Fishy odor with 10% KOH (whiff test) 2

Do not treat asymptomatic women unless they are high-risk pregnant women or undergoing surgical abortion or gynecological procedures. 1

Ensure patients complete the full treatment course even if symptoms resolve early, as incomplete treatment may contribute to recurrence. 1