(See also Overview of Vaginitis Overview of Vaginitis Vaginitis is infectious or noninfectious inflammation of the vaginal mucosa, sometimes with inflammation of the vulva. Symptoms include vaginal discharge, irritation, pruritus, and erythema... read more 
.)
Bacterial vaginosis is the most common infectious vaginitis Overview of Vaginitis Vaginitis is infectious or noninfectious inflammation of the vaginal mucosa, sometimes with inflammation of the vulva. Symptoms include vaginal discharge, irritation, pruritus, and erythema... read more . The pathogenesis is unclear but involves the overgrowth of multiple bacterial pathogens and a decrease in the usual lactobacillus-predominant vaginal flora (1 General reference Bacterial vaginosis is vaginitis due to a complex alteration of vaginal flora in which lactobacilli decrease and anaerobic pathogens overgrow. Symptoms include a gray, thin, fishy-smelling vaginal... read more 
).
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 normally protective lactobacilli.
Risk factors for bacterial vaginosis include 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 . In women who have sex with women, risk increases as the number of sex partners increases. However, bacterial vaginosis can occur in virgins, and treating the 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 sexually transmitted... 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 , posthysterectomy vaginal cuff infection, chorioamnionitis Intraamniotic Infection Intraamniotic infection is infection of the chorion, amnion, amniotic fluid, placenta, or a combination. Infection increases risk of obstetric complications and problems in the fetus and neonate... read more , premature 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 gestation is considered preterm. Prematurity is defined by the gestational age at which infants are born. Previously, any infant weighing < 2.5 kg was termed... 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 malodorous, gray, and thin. Usually, a fishy odor is present, often becoming stronger when the discharge is more alkaline—after coitus and menses. Pruritus, irritation, erythema, and edema are not common.
Diagnosis of Bacterial Vaginosis
Clinical criteria
Vaginal pH and wet mount
For bacterial vaginosis to be diagnosed, 3 of 4 criteria must be present:
Gray discharge
Vaginal secretion pH > 4.5
Fishy odor on the whiff test
Clue cells
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 vaginal discharge, vaginal bleeding, and cervical erythema and friability. Women are tested for infectious... read more 
) and the need for additional testing.
Also, some relatively new diagnostic tests are commercially available for clinical use (1–4 Diagnosis references Bacterial vaginosis is vaginitis due to a complex alteration of vaginal flora in which lactobacilli decrease and anaerobic pathogens overgrow. Symptoms include a gray, thin, fishy-smelling vaginal... read more ).
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 Epub 2012 Apr 25.
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 Print 2018 Jun.
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 Print 2018 Sep.
Treatment of Bacterial Vaginosis
Metronidazole or clindamycin
The following treatments for bacterial vaginosis are equally effective:
Oral metronidazole 500 mg twice a day for 7 days or 2 g once
Metronidazole 0.75% gel 5 g (one applicator full) intravaginally once a day for 7 days
2% clindamycin vaginal cream once a day for 7 days
Oral metronidazole 500 mg twice a day for 7 days is the treatment of choice for patients who are not pregnant, but because systemic effects are possible with oral drugs, topical regimens are preferred for pregnant patients. Women who use clindamycin cream cannot use latex products (ie, condoms or diaphragms) for contraception because the drug weakens latex.
Secnidazole 2 g orally once is another option for treating bacterial vaginosis (1 Treatment references Bacterial vaginosis is vaginitis due to a complex alteration of vaginal flora in which lactobacilli decrease and anaerobic pathogens overgrow. Symptoms include a gray, thin, fishy-smelling vaginal... read more , 2 Treatment references Bacterial vaginosis is vaginitis due to a complex alteration of vaginal flora in which lactobacilli decrease and anaerobic pathogens overgrow. Symptoms include a gray, thin, fishy-smelling vaginal... read more ). Because only one dose is needed, secnidazole may improve patient compliance.
Treatment of asymptomatic sex partners is unnecessary.
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, antibiotics may have to be taken for a long time.
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 Epub 2017 Sep 1.
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
