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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
Topic Resources

Bacterial vaginosis is a dysbiosis, a complex alteration of vaginal flora, in which lactobacilli decrease and anaerobic pathogens overgrow. Symptoms include a yellow-green or gray, thin, malodorous vaginal discharge. Diagnosis is confirmed by evaluation of vaginal secretions. Treatment is usually with oral or topical metronidazole or topical clindamycin.

Anaerobic pathogens that overgrow include Prevotella species, Peptostreptococcus species, Gardnerella vaginalis, Mobiluncus species, and Mycoplasma hominis, which increase in concentration by 10- to 100-fold and replace the lactobacilli that usually maintain a normal vaginal environment.

Risk factors for bacterial vaginosis are the same as those for sexually transmitted infections Overview of Sexually Transmitted Infections Sexually transmitted infection (STI) refers to infection with a pathogen that is transmitted through blood, semen, vaginal fluids, or other body fluids during oral, anal, or genital sex with... read more , including multiple sex partners, sharing of sex toys, and inconsistent or incorrect use of condoms or dental dams. However, bacterial vaginosis can occur in people who have never had vaginal intercourse, and treating a male sex partner does not appear to affect subsequent incidence in sexually active heterosexual women. Use of an intrauterine device is also a risk factor.

Bacterial vaginosis appears to increase the risk of pelvic inflammatory disease Pelvic Inflammatory Disease (PID) Pelvic inflammatory disease (PID) is a polymicrobial infection of the upper female genital tract: the cervix, uterus, fallopian tubes, and ovaries; abscess may occur. PID may be caused by sexually... read more , postabortion and postpartum endometritis Postpartum Endometritis Postpartum endometritis is uterine infection, typically caused by bacteria ascending from the lower genital or gastrointestinal tract. Symptoms are uterine tenderness, abdominal or pelvic pain... read more , and posthysterectomy vaginal cuff infection. In pregnancy, bacterial vaginosis is associated with an increased risk of chorioamnionitis Intraamniotic Infection Intraamniotic infection is infection and resulting inflammation of the chorion, amnion, amniotic fluid, placenta, decidua, fetus, or a combination. Infection increases risk of obstetric complications... read more , prelabor rupture of membranes Prelabor Rupture of Membranes (PROM) Prelabor rupture of membranes is leakage of amniotic fluid before onset of labor. Diagnosis is clinical. Delivery is recommended when gestational age is ≥ 34 weeks and is generally indicated... read more , preterm labor Preterm Labor Labor (contractions resulting in cervical change) that begins before 37 weeks gestation is considered preterm. Risk factors include prelabor rupture of membranes, uterine abnormalities, infection... read more , and preterm birth Preterm Infants An infant born before 37 weeks of gestation is considered preterm. In 2021 in the United States, 10.48% of births were preterm ( 1), and in 2018, 26.53% of births were early term (significantly... read more .

General reference

  • 1. Muzny CA, Schwebke JR: Pathogenesis of bacterial vaginosis: Discussion of current hypotheses. J Infect Dis 214 (Suppl 1):S1–S5, 2016. doi: 10.1093/infdis/jiw121

Symptoms and Signs of Bacterial Vaginosis

Vaginal discharge due to bacterial vaginosis is yellow-green or gray, thin, and malodorous, usually with a fishy odor that often becomes stronger when the discharge is more alkaline—after coitus and during menses.

Pruritus, irritation, erythema, and edema are not common.

Diagnosis of Bacterial Vaginosis

  • Pelvic examination

  • Vaginal pH and microscopy

  • If microscopy is unavailable, sometimes nucleic acid amplification tests (NAATs)

For bacterial vaginosis to be diagnosed, 3 of 4 criteria (Amsel criteria) must be present:

  • Yellow-green or gray discharge

  • Vaginal secretion pH > 4.5

  • Fishy odor on the whiff test (application of potassium hydroxide)

  • Clue cells on saline (0.9%) wet mount

Clue cells (bacteria adhering to epithelial cells and sometimes obscuring their cell margins) are identified by microscopic examination of a saline wet mount.

Presence of white blood cells on a saline wet mount suggests a concomitant infection (possibly trichomonal, gonorrheal, or chlamydial cervicitis Cervicitis Cervicitis is infectious or noninfectious inflammation of the cervix. Findings may include cervical or vaginal discharge and cervical erythema and friability. Diagnosis is with tests for cervical... read more Cervicitis ) and the need for additional testing.

NAATs are commercially available for clinical use (1–4 Diagnosis references Bacterial vaginosis is a dysbiosis, a complex alteration of vaginal flora, in which lactobacilli decrease and anaerobic pathogens overgrow. Symptoms include a yellow-green or gray, thin, malodorous... read more Diagnosis references ). If microscopy is unavailable, the diagnosis is inconclusive, or the patient remains symptomatic, a NAAT should be considered.

Diagnosis references

  • 1. Cartwright CP, Lembke BD, Ramachandran K, et al: Development and validation of a semiquantitative, multitarget PCR assay for diagnosis of bacterial vaginosis. J Clin Microbiol 50 (7):2321–2329, 2012. doi: 10.1128/JCM.00506-12

  • 2. Schwebke JR, Gaydos CA, Nyirjesy P, et al: Diagnostic performance of a molecular test versus clinician assessment of vaginitis. J Clin Microbiol 56 (6):e00252-18, 2018. doi: 10.1128/JCM.00252-18

  • 3. Gaydos CA, Beqaj S, Schwebke JR, et al: Clinical validation of a test for the diagnosis of vaginitis. Obstet Gynecol 130 (1):181–189, 2017. doi: 10.1097/AOG.0000000000002090

  • 4. Coleman JS, Gaydos CA: Molecular diagnosis of bacterial vaginosis: An update. J Clin Microbiol 56 (9):e00342–e00318, 2018. doi: 10.1128/JCM.00342-18

Treatment of Bacterial Vaginosis

  • Metronidazole or clindamycin

The following treatments for bacterial vaginosis are equally effective (see CDC: Sexually Transmitted Infections Treatment Guidelines, 2021):

  • Oral metronidazole 500 mg twice a day for 7 days

  • Metronidazole 0.75% gel 5 g (one applicator full) intravaginally once a day for 5 days

  • 2% clindamycin vaginal cream once a day for 7 days

For topical treatments, metronidazole is preferred; clindamycin is an alternative option.

Oral metronidazole is the treatment of choice for patients who are not pregnant. For pregnant patients, topical regimens are preferred because systemic effects are possible with oral medications.

Women treated with clindamycin cream should not use latex products (ie, condoms or diaphragms) for contraception because the cream weakens latex.

Treatment of sex partners is not recommended.

For vaginitis during the 1st trimester of pregnancy, metronidazole vaginal gel should be used, although treatment during pregnancy has not been shown to lower the risk of pregnancy complications. To prevent endometritis, clinicians may give oral metronidazole prophylactically before elective abortion to all patients or only to those who test positive for bacterial vaginosis.

When treated, symptomatic bacterial vaginosis usually resolves in a few days but commonly recurs. If it recurs often (current infection and at least 2 previous episodes within the previous 12 months), ongoing suppressive antibiotics may be required. Suppressive therapy using the metronidazole gel 2 times a week for 16 weeks may be considered in patients with recurrent bacterial vaginosis (3 Treatment references Bacterial vaginosis is a dysbiosis, a complex alteration of vaginal flora, in which lactobacilli decrease and anaerobic pathogens overgrow. Symptoms include a yellow-green or gray, thin, malodorous... read more Treatment references ).

Treatment references

  • 1. Schwebke JR, Morgan FG Jr, Koltun W, Nyirjesy P: A phase-3, double-blind, placebo-controlled study of the effectiveness and safety of single oral doses of secnidazole 2 g for the treatment of women with bacterial vaginosis. Am J Obstet Gynecol 217 (6):678.e1–678.e9, 2017. doi: 10.1016/j.ajog.2017.08.017

  • 2. Hillier SL, Nyirjesy P, Waldbaum AS, et al: Secnidazole treatment of bacterial vaginosis: A randomized controlled trial. Obstet Gynecol 130 (2):379-386, 2017. doi: 10.1097/AOG.0000000000002135

  • 3. Sobel JD, Ferris D, Schwebke J, et al: Suppressive antibacterial therapy with 0.75% metronidazole vaginal gel to prevent recurrent bacterial vaginosis. Am J Obstet Gynecol 194(5):1283-1289, 2006. doi:10.1016/j.ajog.2005.11.041

Drugs Mentioned In This Article

Drug Name Select Trade
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
Acidophilus, Acidophilus Gold Extra Strength, BioGaia, Culturelle, Culturelle Health & Wellness, Culturelle Health & Wellness Vegetarian, Culturelle Kids, Culturelle Kids Probiotic, Culturelle Kids Pro-well Probiotics, Culturelle Kids Purely Probiotic, Culturelle Kids Regularity, Culturelle Probiotics, Culturelle Probiotics Health & Wellness, Culturelle Probiotics Total Balance, Florajen, Floranex Granules, Lacto Freedom , Mega Probiotic, NewFlora, PROBACAP, Probiotic, Probiotic Acidophilus, REJUVAFLOR, RENEWAFLOR, UpSpring DUAL
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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