Gardnerella Vaginitis (Bacterial Vaginosis)


What Is It?

Bacterial vaginosis is a gynecological condition caused by a change in the type of bacteria found in the vagina. Under normal circumstances, bacteria belonging mostly to the Lactobacillus family live harmlessly in the vagina and produce chemicals that keep the vaginal environment mildly acidic. In bacterial vaginosis, Lactobacillus bacteria are replaced by other types of bacteria that normally are present in smaller concentrations in the vagina. This shift away from Lactobacillus results in bacterial vaginosis.

Scientists do not fully understand the reason behind this change. Risk factors that seem to increase the likelihood of bacterial vaginosis include a history of multiple sex partners, a sexual relationship with a new partner, the use of vaginal contraceptive products that contains the chemical nonoxynol-9 and frequent vaginal douching.

Bacterial vaginosis is the most common cause of abnormal vaginal odor and discharge. For most women, bacterial vaginosis is simply a nuisance, and the goal of treatment is to relieve symptoms.

Bacterial vaginosis commonly is diagnosed during pregnancy. Bacterial vaginosis has been implicated as a risk factor for premature labor and delivery, premature rupture of membranes and postpartum uterine infections. This is why pregnant women may be checked for bacterial vaginosis even when they have no symptoms.


Up to 50 percent of women diagnosed with bacterial vaginosis do not have symptoms. In others, it causes an unpleasant vaginal odor and a white vaginal discharge. For some women, these symptoms are especially bothersome during or after intercourse. The white discharge seen in bacterial vaginosis tends to have a thinner consistency than the “cheesy,” thick discharge seen in vaginal yeast (Candida) infections. Significant irritation of the vulva or pain during intercourse is uncommon with bacterial vaginosis. So if you have these symptoms, your doctor will check for other possible causes.


In addition to asking you to describe the vaginal odor and discharge, your doctor will ask you about your menstrual history (last menstrual period), number of sex partners, previous vaginal or urinary tract infections, history of sexually transmitted infection and pelvic infection, methods of contraception and pregnancy history, and personal hygiene issues such as douching and your use of feminine deodorants, tightly fitting undergarments and tampons. Your doctor also may ask if you have any other diseases, such as diabetes, or if you have used antibiotics recently.

Your doctor can diagnose bacterial vaginosis based on the results of a gynecological examination and laboratory tests of your vaginal fluid. There is no perfect test, but if you have three of the following four criteria, there is a 98 percent chance that you have bacterial vaginosis:

  • White, thin, coating on your vaginal walls during the pelvic exam
  • pH test of vaginal discharge that shows low acidity (pH greater than 4.5)
  • Fishy odor when a sample of vaginal discharge is combined with a drop of potassium hydroxide on a glass slide (the “whiff test”)
  • Clue cells (vaginal skin cells that are coated with bacteria) visible on microscopic exam of vaginal fluid

Your doctor may order other laboratory tests to rule out other causes of vaginal discharge.


Doctors are not exactly sure why bacterial vaginosis develops. Because it occurs more commonly in people who are sexually active, bacterial vaginosis is considered by some to be sexually transmitted. However, bacterial vaginosis also occurs in people who either are not sexually active or have been in long-term monogamous relationships.

Treatment of male sex partners doesn’t necessarily prevent re-infections in women who have had bacterial vaginosis. Scientists currently have no explanation for why some women have problems with recurrent infection, but in some cases treating the male partner may be helpful.

According to experts, having bacterial vaginosis may make it easier for you to be infected with HIV if your sexual partner has HIV. If you already have HIV, then the presence of bacterial vaginosis may increase the chance that you will spread HIV to your sexual partner.


Doctors commonly treat bacterial vaginosis using metronidazole (MetroGel-Vaginal) or clindamycin (Cleocin). Either can be taken by mouth or applied as a vaginal cream or gel, though oral is the preferred treatment. The U.S. Centers for Disease Control and Prevention recommends that all pregnant women with symptoms should be treated with oral medications because the medications are safe and work better than vaginal preparations. Pregnant women who are at high risk of preterm labor and delivery should be tested for bacterial vaginosis and receive treatment even if symptoms are absent.

Routinely screening all women for bacterial vaginosis is not recommended. However, women who undergo certain surgical procedures may be treated if infection is identified. Bacterial vaginosis has been associated with uterine, pelvic, and vaginal-cuff infection in women who have had procedures such as endometrial biopsy, hysterosalpingogram (utero-tubogram), IUD insertion, dilation and curettage (D&C), hysterectomy and Caesarean section.

Currently, doctors do not recommend any routine treatment for the male sex partners of women who have bacterial vaginosis.

When To Call A Professional

Call your doctor whenever you notice any abnormal vaginal odor or discharge, especially if you are pregnant.


Studies show that a seven day treatment with oral metronidazole or a five day treatment with metronidazole vaginal gel is equally effective in non-pregnant women. Clindamycin vaginal cream is slightly less effective than either type of metronidazole. Repeat episodes of bacterial vaginosis occur, but they often improve with re-treatment.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.