What is the best treatment for a vaginal swab positive for Enterococcus faecalis with sensitivities to ampicillin (antibiotic) and amoxicillin (antibiotic)?

Treatment of Vaginal Enterococcus faecalis Infection

Amoxicillin is the preferred treatment for vaginal Enterococcus faecalis infection with sensitivities to both amoxicillin and ampicillin, due to its excellent bioavailability, established efficacy, and favorable safety profile.

Recommended Treatment Regimen

For uncomplicated vaginal E. faecalis infection:

• First-line therapy: Amoxicillin 500 mg orally three times daily for 7 days 1
• Alternative: Ampicillin 500 mg orally four times daily for 7 days

Rationale for Amoxicillin Selection

1. Efficacy considerations:

   • Enterococcus faecalis is highly susceptible to amoxicillin when sensitivity is demonstrated 1
   • Amoxicillin has better oral bioavailability than ampicillin (95% vs 50%)
   • Amoxicillin achieves sufficient tissue concentrations for eradication of E. faecalis 1

2. Pharmacokinetic advantages:

   • Amoxicillin requires less frequent dosing (TID vs QID for ampicillin)
   • Better absorption is not affected by food intake
   • More consistent blood levels with oral administration

3. Clinical evidence:

   • Guidelines recommend amoxicillin as a drug of choice for enterococcal infections 1
   • High clinical and microbiological eradication rates (>86%) have been demonstrated 1

Special Considerations

Determining True Infection vs. Colonization

Before initiating treatment, consider:

• Is the patient symptomatic? (vaginal discharge, irritation, dysuria)
• Is the colony count significant? (50,000-100,000 CFU indicates significant growth)
• Are there other organisms present that might be the primary pathogen?

Alternative Treatments

If amoxicillin/ampicillin cannot be used:

• Nitrofurantoin may be considered for lower genital tract infections with urinary symptoms 2, 3
• Fosfomycin 3g single dose has activity against E. faecalis and may be considered in cases with concurrent urinary symptoms 2

Treatment Failure Considerations

If treatment fails with initial therapy:

• Consider longer duration (10-14 days)
• Consider combination therapy with gentamicin if susceptible (for severe infections only) 1
• Evaluate for structural abnormalities or foreign bodies that may harbor infection

Monitoring and Follow-up

• Clinical improvement should be expected within 48-72 hours
• Consider follow-up culture 1-2 weeks after completing therapy in recurrent cases
• Assess for complete resolution of symptoms

Important Caveats

• Avoid fluoroquinolones despite potential in vitro activity due to increasing resistance and risk of adverse effects 2
• For recurrent infections, investigate underlying causes (anatomical abnormalities, immunosuppression)
• Distinguish between true infection requiring treatment versus colonization that may not require antimicrobial therapy
• High-dose amoxicillin (e.g., 875 mg BID) may be considered for more severe infections 1

In summary, amoxicillin represents the optimal choice for treating vaginal E. faecalis infection when the organism demonstrates sensitivity to both amoxicillin and ampicillin, based on its excellent efficacy, favorable pharmacokinetic profile, and established safety record.