Bacterial vaginosis was previously called nonspecific vaginitis, Haemophilus vaginitis, or Gardnerella vaginitis. Vaginitis is an inflammation of the vagina and vulva that usually causes itching, pain, and vaginal discharge. Bacterial vaginosis is not usually accompanied by inflammation. It is caused by an imbalance of the microorganisms usually found in a healthy vagina.

Bacterial vaginosis (BV) is the most common vaginal infection in women who have not gone through menopause. At least one-third of all vaginal infections are due to bacterial vaginosis. Nearly half of all women with BV have no symptoms of irritating or itchy vaginal discharge. The most distinctive symptom of BV, which helps distinguish it from vaginitis, is a thick, milky vaginal discharge with a strong fishy odor.

A healthy vagina normally contains many bacteria (the most common being Lactobacillus acidophilus) and some other microorganisms. Lactobacillus appears to help prevent other vaginal microorganisms from increasing in numbers great enough to cause a problem. The microorganisms involved in BV include Gardnerella vaginalis and other types of bacteria (Mobiluncus, Bacteroides, and Mycoplasma). For reasons not well understood, the numbers of these organisms increase with BV while the number of lactobacillus organisms decreases.

Most cases of bacterial vaginosis occur in sexually active women between the ages of 15 and 44. Pregnant women and women with a sexually transmitted disease (STD) are especially at risk for getting this infection. Bacterial vaginosis does not usually affect women after menopause.

Pregnant women with BV are at risk for developing an infection of the amniotic fluid and placenta and are more likely to have a preterm labor and birth.

Several methods can be used to diagnose bacterial vaginosis and to distinguish it from vaginitis.

• Wet mount. A sample of vaginal discharge is mixed with a salt solution after placing it on a microscope slide. The prepared slide is examined to identify the bacteria present, to look for white blood cells that indicate an infection, and to look for unusual cells called clue cells. The presence of clue cells is the most reliable indicator of BV.
• Whiff test. Several drops of a potassium hydroxide (KOH) solution are added to a sample of vaginal discharge to determine if a strong fishy odor is produced. A fishy odor on the whiff test suggests BV.
• Vaginal pH. The normal vaginal pH is 3.8 to 4.5. Bacterial vaginosis often causes the vaginal pH to rise above 4.5.
• Gram stain. A sample of the vaginal discharge is placed on a microscope slide. A special dye is applied to the slide, causing certain types of bacteria ("Gram-positive" bacteria) to turn a shade of purple while coloring others ("Gram-negative" bacteria) pink. In bacterial vaginosis, Gram-negative bacteria, especially Gardnerella vaginalis, are most common.
• Oligonucleotide probes. This test detects the genetic material (DNA) of BV bacteria. Oligonucleotide probe testing is very accurate but is not routinely available in most labs.
• Pap test. BV may be detected during routine Pap testing. However, Pap testing is not a standard test to diagnose BV.
• Culture. A culture of vaginal discharge may show heavy growth of Gardnerella vaginalis, which can be associated with BV.

The presence of clue cells, an increased vaginal pH, and a positive whiff test usually are enough evidence to treat for bacterial vaginosis.

Tests for BV are done on a sample of vaginal discharge.

Tests for Bacterial Vaginosis (BV)
Results