Clinical manifestations
BV is characterized by a milky, homogenous, and malodorous vaginal discharge accompanied by vulvovaginal discomfort and vulvar irritation. Vaginal inflammation typically is absent. The associated odor is fishy, and this odor is accentuated when potassium hydroxide (KOH) is added to the vaginal discharge (amine or “whiff” test) or after the patient has coitus. The distinctive odor is due to the release of organic acids and polyamines that are byproducts of anaerobic bacterial metabolism of putrescine and cadaverine. This release is enhanced by exposure of vaginal secretions to alkaline substances such as KOH or semen.
Diagnostic tests and criteria. The diagnosis of BV is made using Amsel criteria or Gram stain with Nugent scoring; bacterial culture is not recommended. Amsel criteria include:
- homogenous, thin, white-gray discharge
- >20% clue cells on saline microscopy (FIGURE 2)
- a pH >4.5 of vaginal fluid
- positive KOH whiff test.
For diagnosis, 3 of the 4 Amsel criteria must be present.17 Gram stain with Nugent score typically is used for research purposes. Nugent scoring assigns a value to different bacterial morphotypes on Gram stain of vaginal secretions. A score of 7 to 10 is consistent with BV.18
Oral and topical treatments
Treatment is recommended for symptomatic patients. Treatment may reduce the risk of transmission and acquisition of other STIs. The TABLE summarizes Centers for Disease Control and Prevention (CDC) guidelines for BV treatment,19 with options including both oral and topical regimens. Oral and topical metronidazole and oral and topical clindamycin are equally effective at eradicating the local source of infection20; however, only oral metronidazole and oral clindamycin are effective in preventing the systemic complications of BV. Oral metronidazole has more adverse effects than oral clindamycin—including nausea, vomiting, diarrhea, and a disulfiram-like reaction (characterized by flushing, dizziness, throbbing headache, chest and abdominal discomfort, and a distinct hangover effect in addition to nausea and vomiting). However, oral clindamycin can cause antibiotic-associated colitis and is more expensive than metronidazole.
Currently, there are no single-dose regimens for the treatment of BV readily available in the United States. Secnidazole, a 5-nitroimidazole with a longer half-life than metronidazole, (17 vs 8 hours) has been used as therapy in Europe and Asia but is not yet available commercially in the United States.21 Hiller and colleagues found that 1 g and 2 g secnidazole oral granules were superior to placebo in treating BV.22 A larger randomized trial comparing this regimen to standard treatment is necessary before this therapy is adopted as the standard of care.
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