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Recurrent Bacterial Vaginosis

Author: Laura Jacques, MD

Mentor: David Eschenbach, MD
Editor: Jonathan Schaffir, MD

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Bacterial vaginosis occurs when there is a shift in the vaginal microbiota from Lactobacillus dominant species to Gardnerella vaginalis and anaerobic bacteria, which may be difficult to culture. Bacterial vaginosis affects 15% to 30% of women. In North America, the prevalence is highest in Black (33%) and Hispanic (31%) populations. 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 usually presents with foul-smelling vaginal discharge; however, up to 50% of infections are asymptomatic. The Amsel diagnostic criteria are used, and bacterial vaginosis is diagnosed by 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 is 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 is as high as 60% by 12 months. Oral tinidazole and secnidazole have more convenient dosing protocols, but otherwise display no advantage in cure or recurrence rates. There is no universally accepted definition for chronic recurrent bacterial vaginosis, but 3 or more episodes in a 12-month period is commonly used. Reasons for recurrence are incompletely understood but may be due to either reinfection or incomplete restoration of normal vaginal flora. 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.

There is no standardized treatment for recurrent bacterial vaginosis. 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 there is a high rate of recurrence by 6 months post treatment. Longer courses of suppressive therapy are being studied but have not demonstrated improved efficacy. Boric acid is used to 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 benefit of vaginal L crispatus probiotic, other oral/vaginal probiotics are not beneficial. Treating male sexual partners is also ineffective. No data are available 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


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