What is the first line treatment for a patient with a moderate amount of bacteria on a wet prep, indicative of a bacterial infection such as bacterial vaginosis or a sexually transmitted infection like gonorrhea or chlamydia?

Treatment for Moderate Bacteria on Wet Prep

For a moderate amount of bacteria on wet prep suggestive of bacterial vaginosis, treat with metronidazole 500 mg orally twice daily for 7 days or clindamycin 300 mg orally twice daily for 7 days. 1

Diagnostic Confirmation

Before initiating treatment, confirm the diagnosis of bacterial vaginosis using Amsel criteria (3 of 4 required): 2

• Homogeneous, thin, milky vaginal discharge 2
• Vaginal pH > 4.5 2
• Positive whiff test (fishy odor on alkalinization with KOH) 3, 2
• Clue cells present on microscopy (>20% of epithelial cells with adherent bacteria) 3, 2

Important caveat: If the wet prep shows normal cervical discharge and no white blood cells, bacterial vaginosis is unlikely and alternative diagnoses should be considered. 1

First-Line Treatment Regimens

Oral Therapy (Preferred)

• Metronidazole 500 mg orally twice daily for 7 days 1
• Alternative: Clindamycin 300 mg orally twice daily for 7 days 1

Intravaginal Therapy (Alternative)

• Metronidazole gel 0.75%, one full applicator (5g) intravaginally daily for 5 days 1
• Clindamycin cream 2%, one full applicator (5g) intravaginally at bedtime for 7 days 1

The 7-day oral regimen is essential for maximal effectiveness, as shorter courses have inferior cure rates. 4

Rule Out Coinfections

Critical step: Test for concurrent sexually transmitted infections, as coinfections occur in approximately 1-2% of cases: 5

• Screen for Chlamydia trachomatis and Neisseria gonorrhoeae using nucleic acid amplification testing 1
• Examine wet prep for Trichomonas vaginalis (motile organisms present in 50-75% of infected cases) 3, 5
• Assess for vulvovaginal candidiasis (hyphae or budding yeast on microscopy, normal pH 3.8-4.2) 3

If Chlamydia is Detected Concurrently

Add azithromycin 1g orally as a single dose OR doxycycline 100 mg orally twice daily for 7 days to the bacterial vaginosis treatment regimen. 6, 7

If Gonorrhea is Detected Concurrently

Add ceftriaxone 125-250 mg intramuscularly as a single dose to cover gonococcal infection. 1

If Trichomonas is Detected Concurrently

Metronidazole 2g orally as a single dose OR metronidazole 500 mg orally twice daily for 7 days will treat both bacterial vaginosis and trichomoniasis simultaneously. 1

Partner Management

Sexual partners should be treated if recurrence is a problem, though bacterial vaginosis is not strictly a sexually transmitted disease. 4, 8 Treatment of partners can reduce recurrence rates, which can reach 80% at 9 months without partner therapy. 8

• Both patient and partner should abstain from sexual intercourse until therapy is completed 6
• For confirmed chlamydia or gonorrhea coinfection, all sexual partners within the previous 60 days must be evaluated and treated 6

Special Populations

Pregnancy

• Pregnant women should receive metronidazole or clindamycin (same regimens as non-pregnant patients) 4
• Avoid doxycycline and quinolones in pregnancy 1
• For chlamydia coinfection in pregnancy: azithromycin 1g orally single dose OR amoxicillin 500 mg orally three times daily for 7 days 6

HIV Infection

Patients with HIV should receive identical treatment regimens as HIV-negative patients. 1, 6

Common Pitfalls

• Failure to complete the full 7-day course reduces cure rates from 80-100% to suboptimal levels 4, 8
• Not treating sexual partners is the most common cause of treatment failure and recurrence 1, 3
• Misdiagnosing mucopurulent cervicitis as simple bacterial vaginosis without testing for gonorrhea and chlamydia can lead to serious complications including pelvic inflammatory disease 1
• Using single-dose metronidazole 2g for bacterial vaginosis is less effective than the 7-day regimen 4
• Recurrence rates approach 80% at 9 months, so patient education about risk factors and partner treatment is essential 8