Bacterial Vaginosis – CDC Diagnosis and Treatment Recommendations

CLINICAL ACTIONS:

Bacterial Vaginosis (BV) occurs when normal hydrogen peroxide producing Lactobacillus sp. is replaced by an overgrowth of facultative anaerobic bacteria. If a woman presents with symptoms, including vaginal discharge, irritation and malodor

• Diagnose BV if 3 of the following (Amsel) clinical criteria are present
  • Homogeneous, thin, white discharge that smoothly coats the vaginal walls
  • More than 20% clue cells (e.g., vaginal epithelial cells studded with adherent coccobacilli) on saline microscopic examination
  • pH of vaginal fluid >4.5
  • Fishy odor of vaginal discharge before or after addition of 10% KOH (i.e., the whiff test),   OR
• Gram stain with Nugent scoring is considered the gold standard to diagnose
  • • Used in research settings; impractical for clinicians so Amsel criteria preferred clinically
    • Assigns a score to various bacterial concentrations seen on gram stain: 0-3 Normal | 4-6 Intermediate | 7-10 Bacterial vaginosis
• Affirm VP III (Becton Dickinson, Sparks, MD), a DNA hybridization probe test for high concentrations of G. vaginalis
• OSOM BV Blue test (Sekisui Diagnostics, Framingham, MA), which detects vaginal fluid sialidase activity, have acceptable performance characteristics compared with Gram stain
• Nucleic Acid Amplification Tests (NAAT) are also available and “can be used as an alternative to clinical testing in settings where pH paper, KOH, and microscopy are not available”
• Do NOT use Pap tests
• Do NOT culture for G. vaginalis given normal vaginal flora is heterogenous

Vaginal wet mount with a NaCl preparation, showing a clue cell at bottom left, and two normal epithelial cells.

SYNOPSIS:

Bacterial Vaginosis (BV) is not caused by a single bacterium, but by high concentrations of facultative anaerobic bacteria (e.g., Prevotella sp. and Mobiluncus sp.), G. vaginalis, Ureaplasma, Mycoplasma, and numerous other anaerobes. BV is associated with multiple or new sex partners, lack of condom use and in particular lack of vaginal lactobacillus. Because BV is not an inflammatory condition, vulvar erythema and edema are not commonly seen, unlike candidiasis and trichomoniasis.

KEY POINTS:

Treatment is recommended for women with symptoms, including discharge, irritation and malodor and may reduce the risk for C. trachomatis, N. gonorrhoeae, T. vaginalis, HIV, and herpes simplex type 2.

Recommended CDC regimens include the following:

• Metronidazole* 500 mg orally twice a day for 7 days OR

• Metronidazole* gel 0.75%, one full applicator (5 g) intravaginally, once a day for 5 days OR

• Clindamycin** cream 2%, one full applicator (5 g) intravaginally at bedtime for 7 days

Alternative Regimens

• Tinidazole* 2 g orally once daily for 2 days OR

• Tinidazole* 1 g orally once daily for 5 days OR

• Clindamycin** 300 mg orally twice daily for 7 days OR

• Clindamycin** ovules 100 mg intravaginally once at bedtime for 3 days
• Secnidazole 2 g orally in a single dose

*Alcohol consumption should be avoided during treatment with oral nitroimidazoles. To reduce the possibility of a disulfiram-like reaction, abstinence from alcohol use should continue for 24 hours after completion of metronidazole and 72 hours after completion of tinidazole.

**Clindamycin ovules use an oleaginous base that might weaken latex or rubber products (e.g., condoms and vaginal contraceptive diaphragms). Use of such products within 72 hours following treatment with clindamycin ovules is not recommended. 

• Test all women with BV for HIV and other sexually transmitted diseases (STDs)

• Follow-up visits are unnecessary if symptoms resolve
• Routine treatment of sex partners in not recommended
• Using a different recommended treatment regimen can be considered in women who have a recurrence
  • Retreatment with the same recommended regimen is an acceptable approach for treating persistent or recurrent BV after the first occurrence
• Recurrent BV: At least 3 documented, separate episodes of BV in one year
  • 0.75% metronidazole gel twice weekly for 4–6 months has been shown to reduce recurrences, although this benefit might not persist when suppressive therapy is discontinued

BV and Preterm Birth

• The USPSTF addresses BV screening during pregnancy and states the following

The USPSTF recommends against screening for bacterial vaginosis in pregnant persons not at increased risk for preterm delivery. (D recommendation)

The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for bacterial vaginosis in pregnant persons at increased risk for preterm delivery. (I statement)

Concurrent Sexual Partner Therapy   

• Based on an RCT, ACOG recommends concurrent male sexual partner therapy
  • For partners of patients with recurrent and symptomatic BV  
  • Male treatment incudes both oral and topical antimicrobial agents 
• ACOG recommends shared decision making regarding concurrent sexual partner therapy for
  • Same sex partners 
  • First occurrence of symptomatic bacterial vaginosis 

• ACOG recommendations based on RCT (Vodstrcil et al. NEJM, 2025)
  • Open-label, randomized controlled trial involving 164 heterosexual couples across five health centers in Australia
  • Women received standard BV treatment
  • Male partners were randomized to either receive oral metronidazole (400 mg) and 2% clindamycin cream applied to the penis, or no treatment
  • Trial stopped at 12 weeks with only 150 couples due to inferiority of standard care
  • Absolute risk difference: −2.6 recurrences per person-year (95% CI, −4.0 to −1.2; P<0.001)
• Limitations of the RCT include
  • Population mostly derived from 1 sexual health service
  • Results reflect outcomes in a higher-risk population that could impact generalizability 

Note: BV partner treatment is not legally or clinically considered expedited partner therapy (EPT) under most state laws or CDC protocols (see ‘Primary Sources – Learn More’ Below for more information on EPT)

Learn More – Primary Sources:

Sexually Transmitted Infections Treatment Guidelines 2021

ACOG Practice Bulletin 215: Vaginitis in Nonpregnant Patients

USPSTF: Screening for Bacterial Vaginosis in Pregnant Persons to Prevent Preterm Delivery

Male-Partner Treatment to Prevent Recurrence of Bacterial Vaginosis (Vodstrcil et al. NEJM, 2025)

ACOG Clinical Update: Concurrent Sexual Partner Therapy to Prevent Bacterial Vaginosis Recurrence

Related ObG Topics:

Screening for Sexually Transmitted Infections – Who, When and How Often?

Diagnosing Vaginitis – Why the Office Visit Still Matters

STI Screening in Pregnancy: CDC Recommendations

FDA Approves Secnidazole: Single-Dose Oral Treatment for BV

Sexually Transmitted Infections and Partner Notification