Bacterial vaginosis


Bacterial vaginosis (BV) is one of the commonest causes of abnormal vaginal discharge in women. Symptoms include abnormal discharge, (typically whitish or grey) and/or an unpleasant odour classically described as fishy. Up to 50 % of women with BV are asymptomatic. Risk factors for BV include having increased numbers of sexual partners, a new sex partner, and inconsistent condom use.
BV is a polymicrobial condition characterized by changes in the normal vaginal flora, with reduction in key lactobacillus species and high concentrations of anaerobic bacteria such as Gardnerella vaginalis, Atopobium vaginae, Prevotella sp and uncultivatable and fastidious species. BV has been associated with adverse pregnancy outcomes, including miscarriage, preterm labour, and ascending infection following invasive gynaecological procedures such as termination of pregnancy and IUD insertion.


Clinical diagnosis of BV is made using Amsel’s criteria and 3 or 4 of the following criteria must be present: 

  1. Clinician observed vaginal discharge - thin,white, adherent, homogeneous appearance.
  2. Vaginal pH of >4.5. 
  3. The presence of “clue cells” on a gram stain or wet prep from a high vaginal swab.
  4. Positive amine (whiff) test – note if you can smell the odour on examination this can be recorded as a positive whiff test. 

Laboratory diagnosis is made by grading the gram stain of a high vaginal swab according to Nugent’s criteria. A score of 7-10 is diagnostic of BV, and 4-6 is classified as intermediate flora. Approximately 50% of women with intermediate flora by the Nugent method will have BV by the Amsels method. Therefore at MSHC we recommend applying both Amsels and Nugent methods for the diagnosis of BV.


Treatment is recommended for symptomatic women, but the benefit of treatment has not been established for asymptomatic women, unless they are undergoing invasive gynaecological procedures such as termination of pregnancy or IUD insertion or are pregnant and have a history of pre-term delivery.

Treatment of male sexual partners has not been recommended as prior published studies indicated no benefit. However these trials were systematically flawed underpowered and new international clinical trials of male partner treatment are underway including at MSHC to provide an accurate evidence base for treatment guidelines. No trials of female partner treatment have been conducted to inform female partner treatment. However, high concordance for BV has been reported within female-female partnerships. Testing of female partners should be offered in order to detect and treat BV in the partner, but there is no current evidence to show benefit in reducing BV recurrence in a woman through additional treatment of her female partner. Further studies are required to improve the evidence base.

Recommended treatment in women who are not pregnant

  • Metronidazole 400mg twice daily for 7 days or
  • Clindamycin vaginal cream PV each night for 7 nights*
    *Clindamycin cream is oil based and can weaken condoms.

Metronidazole gel 0.75%, one applicator (5g) intravaginally, once daily for 5 days is equally effective but only available as a non-PBS subsidized private script.

Alternative regimens include tinidazole (1g orally daily for 5 days) and oral clindamycin (300mg bd for 7 days), and single doses of metronidazole (2g) or tinidazole (2g) but these are associated with higher recurrence rates of BV.
No studies currently support the use of available intravaginal lactobacillus or lactic or acetic acid formulations.
Both tinidazole and metronidazole can cause nausea and the patient should be advised to have her medication with food and to avoid drinking any alcohol whilst on treatment.   

Treatment in pregnancy
Treatment is recommended for all symptomatic pregnant women. There is insufficient data to recommend screening and treatment of asymptomatic pregnant women for BV. The only established benefit of treatment in pregnancy is alleviation of symptoms. Meta-analysis has not shown benefit of antibiotic therapy in reduction of pre-term delivery, although studies of women at high risk of pre-term delivery have yielded mixed results. Oral therapy has not been shown to be superior to topical vaginal therapy in pregnancy. Therefore both the oral and topical regimens recommended in non-pregnant women can be used. Metronidazole is category B2 but meta analysis has not demonstrated an association with teratogenic or mutagenic effects in neonates. Clindamycin is category A. Tinidazole is category C and should be avoided in pregnancy.

For women with multiple BV recurrences:
Limited data are available for the treatment of recurrent BV and are largely based on expert opinion. . However, in women with a history of recurrence, Metronidazole gel twice weekly for 4-6 months has been shown to reduce BV recurrence compared to placebo when administered after first line antibiotic therapy, but this benefit occurs on treatment and does not persist when discontinued.

The content of these treatment guidelines is for information purposes only. The treatment guidelines are generic in character and should be applied to individuals only as deemed appropriate by the treating practitioner on a case by case basis. Alfred Health, through MSHC, does not accept liability to any person for the information or advice (or the use of such information or advice) which is provided through these treatment guidelines. The information contained within these treatment guidelines is provided on the basis that all persons accessing the treatment guidelines undertake responsibility for assessing the relevance and accuracy of the content and its suitability for a particular patient. Responsible use of these guidelines requires that the prescriber is familiar with contraindications and precautions relevant to the various pharmaceutical agents recommended herein.

Last Updated April 2018