Bacterial vaginosis, also referred to as anaerobic vaginosis, is a cause of vaginal discharge but is non-sexually transmitted. It is common with a prevalence of up to 20%. bacterial vaginosis is characterized by an altered vaginal bacterial flora with a preponderance of anaerobic bacteria, such as Mobiluncus spp., Gardnerella vaginalis, Bacteroides spp. and Mycoplasma spp., and an absence of lactobacilli. The etiology of bacterial vaginosis is poorly understood. Although it is related to sexual activity, a sexually transmitted pathogen has not been identified and bacterial vaginosis can occur in women who are not sexually active. There is an association with vaginal douching and the use of IUDs.

bacterial vaginosis may predispose women to postoperative pelvic infection, endometritis after birth or termination of pregnancy, chorioamnionitis, second trimester loss, premature birth and rupture of membranes. It is also believed to play a role in the pathogenesis of pelvic inflammatory disease.

Vaginal discharge and fishy odor may occur but approximately half of all women with bacterial vaginosis have no symptoms. As bacterial vaginosis does not cause inflammation of the vagina and vulva, a complaint of soreness or pruritis should lead to consideration of coexistent conditions. The clinical findings are malodor and thin, grey, homogenous vaginal discharge.


The diagnosis of bacterial vaginosis is made if three of the following four criteria are present: (1) thin white/grey discharge; (2) vaginal pH > 4.5; (3) positive amine test; and (4) clue cells detected on microscopy of a wet mount or gram stain. Clue cells are vaginal epithelial cells coated in Gram-variable bacilli that have a characteristic appearance on microscopy. Where immediate microscopy is not available, the history, clinical findings and a raised vaginal pH suffice for a presumptive diagnosis. Setting up a culture for Gardnerella vaginalis is not helpful in the diagnosis of bacterial vaginosis.


Women with a diagnosis of bacterial vaginosis should be offered treatment (Table Treatment of bacterial vaginosis), even if they do not report symptoms as some may not regard their discharge as abnormal or are too embarrassed to mention symptoms such as odor. Treatment is advised for women with bacterial vaginosis who are pregnant, especially if they have symptoms, a history of late miscarriage or premature labor. The value of routinely screening asymptomatic women in pregnancy has not yet been demonstrated.

Table Treatment of bacterial vaginosis

Non-pregnant women  
Metronidazole orally 400 mg twice daily for 7 days
Metronidazole orally 2 g as a single dose
Clindamycin 2% vaginal cream* One applicator full each night for 7 days
Pregnant women (or suspected pregnancy)  
Metronidazole orally 400 mg twice daily for 7 days

*Clindamycin cream may and cervical caps and is weaken latex condoms, diaphragms contraindicated in pregnancy

Bacterial vaginosis may resolve spontaneously but recurrences are common and frequently noticed after menstruation or intercourse. Treating the male partner(s) does not prevent recurrence. Follow-up tests are not performed if the patient is no longer symptomatic, except in pregnant women with a history of late miscarriage or premature labor who should be re-tested after 1 month.

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