What is bacterial vaginosis and how is it treated?

Bacterial Vaginosis: Definition and Treatment

Bacterial vaginosis (BV) is a clinical syndrome resulting from replacement of normal H2O2-producing Lactobacillus species in the vagina with high concentrations of anaerobic bacteria, and should be treated with oral metronidazole 500 mg twice daily for 7 days as first-line therapy for symptomatic women. 1

What is Bacterial Vaginosis?

BV is characterized by an imbalance in the normal vaginal bacterial flora where beneficial Lactobacillus species are replaced by:

• Anaerobic bacteria (e.g., Prevotella and Mobiluncus species)
• Gardnerella vaginalis
• Mycoplasma hominis

This condition is the most prevalent cause of vaginal discharge and malodor, though approximately half of women who meet clinical criteria for BV are asymptomatic 1. While BV is associated with sexual activity (women who have never been sexually active are rarely affected), it is not considered exclusively a sexually transmitted disease 1.

Diagnostic Criteria

BV can be diagnosed using clinical criteria (Amsel's criteria) or Gram stain. Clinical diagnosis requires three of the following four symptoms or signs:

1. A homogeneous, white, non-inflammatory discharge that adheres to vaginal walls
2. Presence of clue cells on microscopic examination
3. Vaginal fluid pH greater than 4.5
4. Fishy odor of vaginal discharge before or after addition of 10% KOH (whiff test)

Gram stain evaluation of vaginal smear (Nugent score) is an acceptable laboratory method for diagnosing BV. Culture of G. vaginalis is not recommended as a diagnostic tool because it is not specific 1.

Treatment Recommendations

First-line Treatment for Non-pregnant Women:

• Metronidazole 500 mg orally twice daily for 7 days 1

Alternative Regimens:

• Clindamycin cream 2%, one full applicator (5 g) intravaginally at bedtime for 7 days
• Metronidazole gel 0.75%, one full applicator (5 g) intravaginally twice daily for 5 days
• Metronidazole 2 g orally in a single dose (lower cure rate: 84% vs. 95% for 7-day regimen)
• Clindamycin 300 mg orally twice daily for 7 days
• Tinidazole 2 g once daily for 2 days or 1 g once daily for 5 days 2

Important Treatment Considerations:

• Patients should avoid alcohol during treatment with metronidazole and for 24 hours afterward 1
• Clindamycin cream is oil-based and might weaken latex condoms and diaphragms 1
• Only symptomatic women require treatment 1
• Treatment of male sex partners has not been shown to be beneficial and is not recommended 1

Special Populations

Pregnant Women:

• First trimester: Clindamycin vaginal cream (preferred due to metronidazole contraindication) 1
• Second and third trimesters: Oral metronidazole can be used 1
• High-risk pregnant women (previous preterm birth): Metronidazole 250 mg orally three times daily for 7 days 3

Allergy or Intolerance to Metronidazole:

• Clindamycin cream is preferred 1
• Metronidazole gel can be considered for patients who don't tolerate systemic metronidazole, but those with allergy to oral metronidazole should not use metronidazole vaginally 1

Recurrent BV

Recurrence of BV is common, with 50-80% of women experiencing recurrence within a year of treatment 4. For recurrent BV:

• Extended course of metronidazole (500 mg twice daily for 10-14 days)
• If ineffective, metronidazole vaginal gel 0.75% for 10 days, followed by twice weekly for 3-6 months 5

Clinical Implications and Complications

BV has been associated with:

• Endometritis
• Pelvic inflammatory disease (PID)
• Vaginal cuff cellulitis following invasive procedures
• Adverse pregnancy outcomes in high-risk women

Treatment of BV before surgical abortion procedures may reduce post-abortion PID 1.

Follow-Up

• Follow-up visits are not necessary if symptoms resolve 1
• No long-term maintenance regimen is currently available for preventing recurrence 1

Emerging Approaches

Research into alternative approaches for BV management includes:

• Probiotics
• Vaginal microbiome transplantation
• pH modulation
• Biofilm disruption
• Behavioral modifications (smoking cessation, condom use) 4

However, antimicrobial therapy remains the mainstay of treatment for BV based on current evidence 5.