Bacterial vaginosis

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  • Accounts for up to 50% of cases of vaginitis
  • Associated with preterm labor and premature rupture of membranes

Clinical Features

  • whitish-gray discharge and odor
    • Lack of discharge makes diagnosis less likely
  • May have history of "physiologic whiff test" after contact with male ejaculate which is alkaline (like KOH)

Differential Diagnosis




A "clue cell": note effacement of borders by bacteria, as compared to normal epithelial cells below.
Normal vaginal epithelial cells on wet mount: note clean borders. Presence of lactobacilli (tiny rods) is normal.
  • Wet mount shows clue cells: vaginal epithelial cells with "stippled appearance" due to coverage by bacteria
  • Whiff Test: fishy odor with 10% KOH prep
  • CDC recommends testing all women with BV for HIV and other STDs [1]

Amsel criteria for diagnosis (3/4 must be present)

  • Homogeneous, thin, gray-white discharge
  • Positive whiff test
  • Vaginal pH>4.5
  • Clue cells on wet mount (at least 20% of epithelial cells)


  • No need to treat if asymptomatic (even if pregnant)
  • Do NOT need to treat sexual partner


First Line Therapy[2]

  • Metronidazole 500 mg PO BID for 7 days OR
  • Metronidazole gel 0.75%, one full applicator (5 g) intravaginally, qd for 5 days OR
  • Clindamycin cream 2%, one full applicator (5 g) intravaginally qHS for 7 days

Alternative Regimin

  • Tinidazole 2 g PO qd for 2 days OR
  • Tinidazole 1 g PO qd for 5 days OR
  • Clindamycin 300 mg PO BID for 7 days OR
  • Clindamycin ovules 100 mg intravaginally qHS for 3 days (do not use if patient has used latex condom in last 72 hrs)


Prophylaxis (Sexual Assault)


  • Discharge

See Also


  1. 1.0 1.1 1.2 1.3 CDC Pregnancy BV Treatment
  2. Workoski KA and Bolan GA. Sexually transmitted diseases treatment guidelines, 2015. MMWR Recommen and Reports. 2015; 64(3):1-140.