A polymicrobial clinical syndrome caused by a profound change in vaginal microbiota from a Lactobacillius dominant state to one with high diversity and loads of anaerobic bacteria including Gardnerella vaginalis, Atopobium vaginae, Mobiluncus spp, Prevotella spp, and other BV-associated bacteria (BVAB). This change is accompanied by a rise in vaginal pH and increased amines which produce odour. Studies have identified a polymicrobial biofilm adherent to vaginal epithelial cells of women with BV which is absent in controls.
Symptoms |
Offensive ‘fishy’ vaginal discharge |
Thin white homogenous discharge |
Can cause mild vulval irritation |
Complications |
Bacterial vaginosis is associated with increased risk of spontaneous abortion, premature labour, chorioamnionitis, postpartum endometritis and pelvic inflammatory disease (PID); especially following termination of pregnancy (TOP), intra-uterine device (IUD) insertion or other instrumentation). BV is associated with a 2-3 fold increased risk of acquiring STIs including chlamydia, gonorrhoea, herpes simplex type 2 and HIV infection, and increases the risk of HIV transmission to male partners. |
The diagnosis of BV is usually made in clinical settings using the Amsels or modified Amsels criteria;
A diagnosis is made if 3 or 4 of the following criteria are present:
1. Thin white/grey homogenous discharge –
2. Vaginal fluid raised pH (pH>4.5) – using pH paper
3. Genital malodour
4. Clue cells on gram stain – this last criterion will be able to be reported by the laboratory on the slide collected below.
Test | Site/Specimen | Consideration |
---|---|---|
Microscopy of high vaginal smear | High vaginal swab | In general practice, prepare a non-stained microscopy slide at the bedside and send to the laboratory with a request for Gram stain and microscopy. |
Whiff test | Vaginal fluid | Odour during examination indicates a positive whiff test. |
pH | Vaginal fluid | Normal vaginal pH < 4.5. pH >4.5 indicative of bacterial vaginosis. |
Clinician collected | Self-collection
See STI Atlas for images.
Principal Treatment Option | ||
---|---|---|
Situation | Recommended | Alternative |
Symptomatic bacterial vaginosis | Metronidazole 400mg PO, BD with food for 7 days. OR Metronidazole 0.75% gel 5g, intravaginally nocte for 5 nights (not on PBS). OR Clindamycin 2% vaginal cream 5g, intravaginally nocte for 7 days (not on PBS). OR Clindamycin 300mg PO, BD for 7 days. |
Metronidazole 2g PO, stat. |
Women undergoing gynaecological procedures |
Metronidazole 400mg PO, BD with food for 5 days. |
Metronidazole 2g PO, stat. |
Treatment is predominantly aimed at alleviating symptoms and recurrence. Treatment is indicated in:
1. symptomatic women
2. Women undergoing an invasive upper genital tract procedure. (Oral treatment is recommended)
3. women requesting treatment
Situation | Recommended |
---|---|
Breastfeeding | Consider intravaginal treatment. Metronidazole may affect taste of breast milk; avoid high doses in breastfeeding. |
Pregnant women ![]() |
Treatment for pregnant women is the same as the principle treatment options for non-pregnant women. Treatment is recommended for all pregnant women with symptoms, although the evidence is conflicting in terms of the benefits of treatment on the outcomes of pregnancy. Women undergoing termination of pregnancy should be treated to reduce risk of post-termination PID. |
Allergy to principal treatment choice |
If allergy to nitroimidazoles, use clindamycin. |
Alcohol |
Alcohol should be avoided with metronidazole use due to the possibility of a disulfiram-like action. There are no data on the risks of alcohol with intravaginal metronidazole gel, but it is not recommended at present. |
Intravaginal preparations |
May affect condom integrity. |
Not required.
Test of Cure (TOC): Not required
Retesting: If symptoms persist or recur, as it is important to confirm diagnosis and establish a pattern. Consider testing for other STIs, if not undertaken at first presentation, or retesting post the window period.