Bacterial Vaginosis

Also Known As: Bacterial Vaginosis, BV, Vaginal bacteriosis

Bacterial vaginosis (BV) or less commonly vaginal bacteriosis is a disease of the vagina caused by bacteria. According to the U.S. Centers for Disease Control and Prevention (CDC), risk factors for BV include douching and having new or multiple sex partners, although it is unclear what role sexual activity plays in the development of BV. BV is caused by an imbalance of naturally occurring bacterial flora and is often confused with yeast infection (candidiasis), or infection with Trichomonas vaginalis (trichomoniasis), which are not caused by bacteria.

The most common symptom of BV is an abnormal homogeneous off-white vaginal discharge (especially after vaginal intercourse) with an unpleasant smell.[6] This malodorous discharge coats the walls of the vagina, and is usually without irritation, pain or erythema. By contrast, the normal vaginal discharge will vary in consistency and amount throughout the menstrual cycle and is at its clearest about 2 weeks before the period starts.


A healthy vagina normally contains many microorganisms; some of the common ones are Lactobacillus crispatus and Lactobacillus jensenii. Lactobacilli, particularly hydrogen peroxide-producing species, appear to help prevent other vaginal microorganisms from multiplying to a level where they cause symptoms. The microorganisms involved in BV are very diverse, but include Gardnerella vaginalis, Mobiluncus, Bacteroides, and Mycoplasma. A change in normal bacterial flora including the reduction of Lactobacilli, which may be due to the use of antibiotics or pH imbalance, allows more resistant bacteria to gain a foothold and multiply.

Although BV can be associated with sexual activity, there is no clear evidence of sexual transmission.[7][non-primary source needed] It is possible for sexually inactive persons to get infected with bacterial vaginosis. Rather, BV is a disordering of the chemical and biological balance of the normal flora. Recent research is exploring the link between sexual partner treatment and eradication of recurrent cases of BV. Pregnant women and women with sexually transmitted infections are especially at risk for getting this infection. Bacterial vaginosis may sometimes affect women after menopause. A 2005 study by researchers at Ghent University in Belgium showed that subclinical iron deficiency (anemia) was a strong predictor of bacterial vaginosis in pregnant women.[8] A longitudinal study published in February 2006 in the American Journal of Obstetrics and Gynecology showed a link between psychosocial stress and bacterial vaginosis independent of other risk factors.[9][clarification needed]

To make a diagnosis of bacterial vaginosis, a swab from inside the vagina should be obtained. These swabs should be tested for:

  • A characteristic "fishy" odor on wet mount. This test, called the whiff test, is performed by adding a small amount of potassium hydroxide to a microscopic slide containing the vaginal discharge. A characteristic fishy odor is considered a positive whiff test and is suggestive of bacterial vaginosis.
  • Loss of acidity. To control bacterial growth, the vagina is normally slightly acidic with a pH of 3.8–4.2. A swab of the discharge is put onto litmus paper to check its acidity. A pH greater than 4.5 is considered alkaline and is suggestive of bacterial vaginosis.
  • The presence of clue cells on wet mount. Similar to the whiff test, the test for clue cells is performed by placing a drop of sodium chloride solution on a slide containing vaginal discharge. If present, clue cells can be visualized under a microscope. They are so-named because they give a clue to the reason behind the discharge. These are epithelial cells that are coated with bacteria.

Two positive results in addition to the discharge itself are enough to diagnose BV. If there is no discharge, then all three criteria are needed.[10][non-primary source needed] Differential diagnosis for bacterial vaginosis includes the following:[citation needed]

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