(See also Overview of Vaginitis.)
Bacterial vaginosis is the most common infectious vaginitis1).
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, 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, postabortion and postpartum endometritis, and posthysterectomy vaginal cuff infection. In pregnancy, bacterial vaginosis is associated with an increased risk of chorioamnionitis, prelabor rupture of membranes, preterm labor, and preterm birth.
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
By permission of the publisher. From Spitzer M, Mann M. In Atlas of Clinical Gynecology: Gynecologic Pathology. Edited by M Stenchever (series editor) and B Goff. Philadelphia, Current Medicine, 1998.
Image obtained from the Public Health Image Library of the Centers for Disease Control and Prevention.
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) and the need for additional testing.
NAATs are commercially available for clinical use (1–4). 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
The following treatments for bacterial vaginosis are equally effective (see CDC: Sexually Transmitted Infections Treatment Guidelines, 2021):
Treatment of sex partners is not recommended.
3).
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
Key Points
Bacterial vaginosis (BV) is an alteration of the vaginal flora in which anaerobic pathogens overgrow and replace lactobacilli (which usually maintain a healthy vaginal environment).
Risk factors are the same as for sexually transmitted infections (STIs), eg, multiple sex partners, sharing of sex toys, and having an STI increases the risk of BV. However, BV may also occur in women in the absence of sexual activity.
BV increases the risk of pelvic inflammatory disease, postpartum endometritis, and some pregnancy complications, including prelabor rupture of membranes and preterm birth.
Symptoms are vaginal discharge, which is typically thin, yellow-green or gray, and malodorous.
Diagnose by evaluation of vaginal discharge with microscopy for Amsel criteria (at least 3 of 4): yellow-green or gray discharge, pH > 4.5, fishy odor on potassium hydroxide whiff test, and clue cells on saline wet mount.
If the diagnosis is inconclusive or symptoms persist after treatment, test with a nucleic acid amplification test (NAAT).
Treatment of sex partners is not recommended.
