Merck Manual

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Bacterial Vaginosis (BV)


Oluwatosin Goje

, MD, MSCR, Cleveland Clinic, Lerner College of Medicine of Case Western Reserve University

Reviewed/Revised Mar 2023

Bacterial vaginosis is a common condition that occurs when the balance of bacteria in the vagina (vaginal microbiome) is altered.

  • Bacterial vaginosis causes a thin, yellow-green or gray discharge, which may be profuse and have a fishy odor.

  • If symptoms suggest a vaginal infection, doctors examine a sample of the discharge and/or fluid from the cervix and test it for infectious organisms.

  • Treatment is with antibiotics applied as gels or creams or taken by mouth.

  • Bacterial vaginosis is more common in women with a sexually transmitted infection.

Causes of Bacterial Vaginosis

Many different types of bacteria normally reside in the vagina. One type, called lactobacilli, maintains the normal acidity of the vagina. By doing so, lactobacilli help keep the lining of the vagina healthy and prevent the growth of certain bacteria that cause infections. Bacterial vaginosis results when the number of protective lactobacilli decreases and the number of other bacteria that are normally present (such as Gardnerella vaginalis and Peptostreptococcus bacteria) increases.

Bacterial vaginosis is a shift in the balance of bacteria (vaginal microbiome). It is not considered a sexually transmitted infection. Bacterial vaginosis can occur in people who have never or have not recently had sexual activity. However, it is associated with some aspects of sexual activity. A current sexually transmitted infection is a risk factor for developing bacterial vaginosis, and conversely, people with bacterial vaginosis have a higher risk of acquiring a sexually transmitted infection. In some cases of bacterial vaginosis, if treatment is not successful, it is helpful to treat sex partners.

Symptoms of Bacterial Vaginosis

Diagnosis of Bacterial Vaginosis

  • A doctor's evaluation

  • Examination of a sample of the discharge and/or fluid from the cervix

If girls or women have a vaginal discharge that is unusual or that lasts for more than a few days, they should see a doctor.

Doctors suspect bacterial vaginosis based on symptoms, such as a gray or yellow-green vaginal discharge that has a fishy odor. They then ask questions about the discharge and other possible disorders (such as sexually transmitted infections).

To confirm the diagnosis, doctors do a pelvic examination Gynecologic Examination For gynecologic care, a woman should choose a health care practitioner with whom she can comfortably discuss sensitive topics, such as sex, birth control, pregnancy, and problems related to... read more . While examining the vagina, the doctor takes a sample of the discharge with a cotton-tipped swab. The sample is examined under a microscope. With information from this examination, the doctor can often identify the cause of the symptoms. If test results are inconclusive, other tests can be done using the samples obtained during the pelvic examination.

Usually, the doctor also uses a swab to take a sample of fluid from the cervix (the lower part of the uterus that opens into the vagina). This sample is tested for sexually transmitted infections.

To determine whether there are other infections in the pelvis, the doctor checks the uterus and ovaries by inserting the index and middle fingers of one gloved hand into the vagina and pressing on the outside of the lower abdomen with the other hand. If this maneuver causes substantial pain or if a fever is present, other infections may be present.

Treatment of Bacterial Vaginosis

  • Antibiotics

Bacterial vaginosis is treated with an antibiotic (such as metronidazole or clindamycin). Metronidazole taken by mouth is the preferred treatment for women who are not pregnant. Other treatments are metronidazole or clindamycin given as a vaginal medication. Women who use clindamycin cream should not use latex products (such as latex condoms or diaphragms) for birth control because the cream weakens latex.

Another possible treatment is the antibiotic secnidazole. Its advantage is that only one dose is needed.

Did You Know...

  • Some vaginal antibiotic creams used to treat bacterial vaginosis weaken latex condoms and diaphragms.

Doctors prefer to treat pregnant women with metronidazole or clindamycin given as a vaginal medication.

When treated, bacterial vaginosis usually resolves in a few days but commonly recurs. If it recurs often, antibiotics may have to be taken for several weeks or months.

Treatment of sex partners is not recommended.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Flagyl, Flagyl ER, Flagyl RTU, LIKMEZ, MetroCream, MetroGel, MetroGel Vaginal, MetroLotion, Noritate, NUVESSA, Nydamax, Rosadan, Rozex, Vandazole, Vitazol
Cleocin, Cleocin Ovules, Cleocin Pediatric, Cleocin T, CLIN, Clindacin ETZ, Clindacin-P, Clinda-Derm , Clindagel, ClindaMax, ClindaReach, Clindesse, Clindets, Evoclin, PledgaClin, XACIATO
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