Bacterial Vaginosis Overview

Bacterial vaginosis (BV) is characterized by the overgrowth of certain bacteria in the vagina, including Gardnerella vaginalis, Gardneralla mobiluncus, and Mycoplasma hominis. Bacterial vaginosis is often underdiagnosed because many women assume they have a yeast infection and treat symptoms with over-the-counter medications.

Incidence and Prevalence of Bacterial Vaginosis

Bacterial vaginosis accounts for 60 percent of vulvovaginal infections. Young adult women, particularly those who are sexually active, are most commonly affected. According to the Centers for Disease Control and Prevention (CDC), BV is the most common vaginal infection in women who are of childbearing age. In the United States, the condition often develops during pregnancy.

Causes and Risk Factors for Bacterial Vaginosis

Although the cause for bacterial vaginosis is not understood completely, the condition is associated with a change in the natural balance of bacteria in the vagina. Lactobacillus is a helpful type of bacteria that metabolizes glycogen to lactic acid in the vagina and maintains normal vaginal pH. Normal pH levels provide a natural defense against unhealthy bacteria proliferation.

When the defense is weakened, harmful bacteria that also are present in the vagina (e.g., Bacteroides sp, Peptostreptococcus sp, Gardnerella vaginalis, G. mobiluncus, Mycoplasma hominis) proliferate and cause symptoms. About 50 percent of women have G. vaginalis in their vaginal flora but do not develop infection.

Any woman can develop bacterial vaginosis. Broad-spectrum antibiotics may destroy healthy bacteria, disrupt the vagina's normal flora, and promote infection. Douching, overused or retained tampons, intrauterine contraceptive devices (IUDs), diaphragms, contraceptive sponges, and products containing nonoxynol-9 may also disrupt the balance.

The role of sexual activity in the development of BV is not clear. The condition is associated with having multiple sex partners, having a new monogamous sexual relationship, and having a history of STDs. Bacterial vaginosis also can affect women who have never had sexual intercourse.

Signs and Symptoms of Bacterial Vaginosis

Vaginal odor, itching, and irritation are common signs of BV and may be particularly noticeable after intercourse or menses. An unpleasant, fishy odor is common. Vaginal irritation and odor may be accompanied by a smooth, sticky white or gray discharge 4 days to 4 weeks following exposure. Elevated vaginal pH level also can be a sign of BV.

Bacterial Vaginosis Complications

Bacterial vaginosis usually does not cause complications. However, the condition is associated with an increased risk for pelvic inflammatory disease (PID), female infertility, tubal (ectopic) pregnancy, premature birth, and low birth weight in infants born to infected mothers.

BV also may increase the risk for HIV infection in women who are exposed to the human immunodeficiency virus and increases the risk for passing the virus to an uninfected sex partner in women who are HIV positive. Bacterial vaginosis also increases the risk for other sexually transmitted diseases, including chlamydia, gonorrhea, and herpes simplex virus (HSV).

Bacterial Vaginosis Diagnosis

Diagnosis usually involves a pelvic examination and laboratory tests to determine whether the cervix is producing abnormal secretions and to check for other diseases. A sample of vaginal fluid is taken for microscopic examination to confirm the presence of bacteria that are associated with BV.

In some cases, vaginal fluid may be treated with a 10% solution of potassium hydroxide (KOH), which makes the characteristic odor more pronounced, and pH levels are checked. Most physicians recommend a full STD screening.

Treatment for Bacterial Vaginosis

Even though bacterial vaginosis may resolve without treatment, all women who have the condition should be treated to prevent complications. Sex partners may require treatment if infection recurs.

Antibiotics such as metronidazole and clindamycin are generally prescribed to treat BV. These medications may be administered as oral (pill) or topical (cream) treatments. When used topically, side effects such as stinging, burning, and irritation may occur. Douching should be avoided.

In May 2007, the Food and Drug Administration (FDA) approved tinidazole (Tindamax®) for the treatment of bacterial vaginosis. This medication, which also can be prescribed to treat trichomoniasis, is administered once daily for either 5 days or 2 days, depending on the dosage.

Women who are being treated for BV should be sure to take all medication as directed, even if symptoms of the condition improve or resolve. In some cases, bacterial vaginosis recurs following treatment.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 10 Jun 1998

Last Modified: 21 Oct 2014