bacterial vaginosis (BV)

Last edited 07/2021 and last reviewed 06/2022

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
• treating partners does not reduce relapse

Reference:

1. Drug and Therapeutics Bulletin 1998; 36 (5): 33-5.
2. FSRH and BASHH Guidance (February 2012) Management of Vaginal Discharge in Non-Genitourinary Medicine Settings.
3. Public Health England (June 2021). Managing common infections: guidance for primary care