This is vaginitis that is caused by a synergic mixture of anaerobic, micro-aerophilic and CO2-dependent bacteria. These species are present in small numbers in most normal women. However, in larger numbers the normal lactobacillary flora of the vagina is disrupted and bacterial vaginosis occurs.
Bacterial vaginitis is associated with an increased risk of preterm birth and infective complications following gynaecological surgery (1).
BV is the commonest cause of abnormal vaginal discharge in women of reproductive age
- prevalence varies and may be influenced by behavioural and/or sociodemographic factors
- can occur and remit spontaneously and is characterised by an overgrowth of mixed anaerobic organisms that replace normal lactobacilli, leading to an increase in vaginal pH (>4.5)
Gardnerella vaginalis is commonly found in women with BV but the presence of Gardnerella alone is insufficient to constitute a diagnosis of BV because it is a commensal organism in 30-40% of asymptomatic women (2)
- other organisms associated with BV include Prevotella species, Mycoplasma hominis and Mobiluncus species
Sexually transmitted or not? (2)
- reports of BV occurring in virgins led to the belief that BV was not an STI
- however, there is a growing body of evidence that suggests a link with sexual behaviour.
- A study that took account of a wider range of sexual activities, including oral and digital intercourse, did not find any cases of BV in truly sexually inexperienced women
- thus BV is considered to be 'sexually associated' rather than truly 'sexually transmitted'
- some evidence that consistent condom use may help to reduce BV prevalence
Key points (3):
- oral metronidazole is as effective as topical treatment, and is cheaper
- 7 days results in fewer relapses than 2g stat at 4 weeks
- pregnant/breastfeeding: avoid 2g dose of metronidazole
Treatment of male sexual partner(4):
- an open label RCT (164 couples in a monogamous relationship) found antimicrobial treatment of the male partner combined with first line antimicrobials for the woman reduced recurrence at 12 weeks vs treatment of the woman alone (35% vs 63%,-2.6 recurrences/person/year p<0.001)
- addition of combined oral and topical antimicrobial therapy for male partners to treatment of women for bacterial vaginosis resulted in a lower rate of recurrence of bacterial vaginosis within 12 weeks than standard care
- antimicrobial treatment for the male partner was metronidazole 400 mg oral tablets and 2% clindamycin cream applied to penile skin, both twice daily for 7 days
Reference:
- Drug and Therapeutics Bulletin 1998; 36 (5): 33-5.
- FSRH and BASHH Guidance (February 2012) Management of Vaginal Discharge in Non-Genitourinary Medicine Settings.
- Public Health England (June 2021). Managing common infections: guidance for primary care
- Vodstrcil LA et al. Male-Partner Treatment to Prevent Recurrence of Bacterial Vaginosis. N Engl J Med 2025;392:947-957