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Recurrent Bacterial Vaginosis

Author: Laura Jacques, MD

Mentor: David Eschenbach, MD
Editor: Katherine Rivlin, MD

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Bacterial vaginosis occurs when the vaginal microbiota dominant species shifts from Lactobacillus to Gardnerella vaginalis and anaerobic bacteria. Bacterial vaginosis affects 15% to 30% of individuals. Risk factors include cigarette smoking, unprotected intercourse, douching, and intrauterine device use. Bacterial vaginosis is linked to increased risk for sexually transmitted infections, surgical infections, and pregnancy complications such as preterm delivery and intrapartum infection. Recurrent bacterial vaginosis can negatively affect patients’ self-esteem, sex life, and overall quality of life.

Symptomatic bacterial vaginosis can present with foul-smelling vaginal discharge; however, up to 50% of infections are asymptomatic. The Amsel criteria for diagnosing bacterial vaginosis require the presence of 3 of the following 4 criteria:

  • Vaginal pH >4.5
  • Thin, watery discharge
  • >20% clue cells on wet mount
  • Positive "whiff" test (amine odor present with addition of KOH)

The gold standard for diagnosis requires assessing the Nugent score (score system based on morphology of Lactobacillus and other morphotypes) on Gram stain. If microscopy is not available, a vaginal pH greater than 4.5 has 97% sensitivity and 64% specificity, while a pH less than 4.4 and a negative whiff test has a 98% negative predictive value. To avoid falsely elevated pH from cervical mucus, discharge should be sampled from the vaginal mucosa midway between the introitus and cervix, using a cotton-tipped swab. 

Oral or vaginal metronidazole or vaginal clindamycin cures acute bacterial vaginosis in 80% to 90% of cases; however, recurrence can occur up to 60% of the time by 12 months. Oral tinidazole and secnidazole have more convenient dosing protocols, but otherwise display no advantage in cure or recurrence rates. While no universally accepted definition for chronic recurrent bacterial vaginosis exists, 3 or more episodes in a 12-month period is commonly used. Recurrence may occur due to either reinfection or incomplete restoration of normal vaginal flora with prior therapy. Relapse may occur due to antibiotic resistance or the development of a biofilm. Biofilms are produced by G vaginalis and consist of an assemblage of microbes within a surface-associated extracellular matrix that acts to inhibit antibiotic penetration.

No standardized treatment for recurrent bacterial vaginosis exists. Vaginal metronidazole 0.75% gel given once daily for 10 days and then twice weekly for 16 weeks demonstrates a 70% protection rate compared with placebo, but the recurrence by 6 months post treatment is high. Longer courses of suppressive therapy have not demonstrated improved efficacy. Boric acid can disrupt biofilms and enhance antibiotic efficacy. Oral metronidazole, 500 mg daily, for 7 days followed by vaginal boric acid capsules, 600 mg twice daily, for 21 days is another treatment option with recurrence rates of 30% by 6 months post treatment. While preliminary data suggest a benefit of vaginal L crispatus probiotic, other oral/vaginal probiotics are not beneficial. A single-dose of metronidazole 1.3% gel may be superior as compared to other regimens of longer duration.  Treating male sexual partners is also ineffective. No data exist regarding the efficacy of treating asymptomatic female partners of patients with recurrent bacterial vaginosis, but symptomatic female partners should be treated. Routine screening and treatment of bacterial vaginosis during pregnancy does not prevent preterm delivery. Symptomatic pregnant patients with bacterial vaginosis should be treated with oral metronidazole, 500 mg twice daily or 250 mg 3 times daily, for 7 days.

Further Reading:

Vaginitis in Nonpregnant Patients: ACOG Practice Bulletin, Number 215. Obstet Gynecol. 2020 Jan;135(1):e1-e17. doi: 10.1097/AOG.0000000000003604. PMID: 31856123.

Workowski KA, Bachmann LH, Chan PA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021 Jul 23;70(4):1-187. doi: 10.15585/mmwr.rr7004a1. PMID: 34292926; PMCID: PMC8344968.

Initial Publication March 2022, Revised January 2024


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