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Key Features

  • Defined as a polymicrobial infection of the vagina caused by an imbalance of the normal bacterial vaginal flora

  • The altered flora has a paucity of hydrogen peroxide–producing lactobacilli and increased concentrations of anaerobic bacteria (Prevotella sp and Mobiluncus sp), Gardnerella vaginalis, Ureaplasma, and Mycoplasma

  • Whether bacterial vaginosis is sexually transmitted is unclear, but it is associated with having multiple sex partners and increased risk of other sexually transmitted infections

  • Associated with premature labor, preterm delivery, intra-amniotic infection, and postpartum endometritis in pregnant females

  • Associated with PID and urinary tract infections in nonpregnant individual

Clinical Findings

  • Most common symptom is a copious, malodorous, homogeneous thin gray-white vaginal discharge

  • Patients may report vaginal itching or dysuria

  • A fishy odor may be most noticeable after intercourse or during menses


  • Clinical criteria

    • Presence of thin, white discharge that smoothly coats the vaginal walls

    • Fishy (amine) odor before or after the addition of 10% KOH (whiff test)

    • pH of vaginal fluid > 4.5 determined with narrow-range pH paper

    • Presence of "clue cells" on microscopic examination; clue cells are squamous epithelial cells that have multiple bacteria adhering to them, making their borders irregular and giving them a speckled appearance

  • Diagnosis requires three out of four criteria, although many female patients who fulfill these criteria have no discharge or other symptoms


  • Recommended

    • Metronidazole, 500 mg orally twice a day for 7 days or

    • Metronidazole, 0.75% gel, 5 g intravaginally once daily for 5 days or

    • Clindamycin cream, 2%, one applicator intravaginally at bedtime for 7 days

  • Alternatives

    • Clindamycin, 300 mg orally twice a day for 7 days or

    • Clindamycin ovule, 100 mg intravaginally once at bedtime for 3 days or

    • Tinidazole, 2 g orally once daily for 2 days or

    • Tinidazole, 1 g orally once daily for 5 days

  • Follow-up visits

    • Unnecessary if symptoms resolve

    • Recommended for high-risk patients 1 month after treatment

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