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Bacterial vaginosis

What is bacterial vaginosis?

Bacterial vaginosis is a common cause of abnormal vaginal discharge and malodour in women of reproductive age. In some women however there will be no symptoms. It is not sexually transmitted or contagious. It was previously referred to as nonspecific vaginitis.

What is the cause of bacterial vaginosis?

Bacterial vaginosis is due to a disturbance of normal bacterial equilibrium in the vagina. Lactobacilli are usually the most common bacteria in the vagina. In bacterial vaginosis, there is an overgrowth of other bacteria, especially Gardnerella, Bacteroides, Peptostreptococci and Mobilunculus species. These are anaerobic bacteria, i.e., they grow in the absence of oxygen.

Predisposing factors include recent antibiotic use, decreased oestrogen production, intrauterine device (IUD) and an increased number of sexual partners.

Clinical features

The odour of the creamy white foamy discharge is the most common complaint, with a positive 'whiff' test. The vulva and vagina are not inflamed so the condition rarely causes itching and it does not result in soreness.

In most women there are no complications. There are some risks in pregnancy including premature labour and inflammation around the fetus (chorioamnionitis). There may also be an association with pelvic inflammatory disease.

How is the diagnosis made?

In bacterial vaginosis, a vaginal smear shows the normal vaginal lactobacilli are replaced by multiple small cocci. These are small round bacteria whereas lactobacilli are elongated. Clue cells are also seen; these are epithelial cells from the lining of the vagina with many of the cocci adherent to their edge. Vaginal pH is elevated (>4.5) in most patients, unlike in vulvovaginal candidiasis when it is reduced below 4.5.

Treatment

Bacterial vaginosis naturally fluctuates so treatment is not always necessary, particularly if there are no symptoms. Intravaginal clindamycin or oral antibiotics (metronidazole) can be prescribed and may reduce vaginal discharge. Treatment is recommended during pregnancy to reduce the risk of complications related to infection.