What is the recommended dose of amoxicillin (amoxicillin) for a patient with a vaginal infection caused by Enterococcus faecalis?

Amoxicillin Dosing for Vaginal Enterococcus faecalis Infection

For uncomplicated vaginal infection caused by Enterococcus faecalis, amoxicillin 500 mg orally three times daily for 7 days is the recommended first-line treatment. 1, 2

Rationale for This Regimen

• E. faecalis is typically fully susceptible to amoxicillin, with MICs generally ≤8 mg/L, making it highly effective for urogenital infections 3, 1
• Amoxicillin achieves high concentrations in urogenital tissues, which is critical for eradicating E. faecalis from the vaginal tract 1
• Amoxicillin is preferred over penicillin G because MICs are two to four times lower, providing superior activity against enterococci 3, 4
• Clinical cure rates of 80-90% can be expected with this standard dosing regimen 1

Treatment Duration and Monitoring

• Complete the full 7-day course even if symptoms resolve earlier to prevent relapse and resistance development 1, 2
• If symptoms persist after treatment completion, obtain cultures to confirm microbiological cure and assess for antimicrobial resistance 1

Alternative Regimens for Special Circumstances

For Beta-Lactamase Producing Strains

• Switch to amoxicillin-clavulanate 500 mg orally three times daily for 7 days if beta-lactamase production is detected 1
• Note that beta-lactamase production in E. faecalis is rare but should be considered if treatment fails 3

For Penicillin Allergy

• Nitrofurantoin 100 mg orally every 6 hours for 7 days is an effective alternative 1, 2
• Fosfomycin 3 g orally as a single dose can be used for uncomplicated infections 1, 2

For Vancomycin-Resistant E. faecalis (VRE)

• High-dose amoxicillin 500 mg orally every 8 hours may still be effective due to high urogenital concentrations, even in VRE strains 2
• Linezolid 600 mg orally every 12 hours for 7-10 days is recommended if amoxicillin fails 1

Critical Pitfalls to Avoid

• Do not underdose: The full 500 mg three times daily is essential—lower doses risk treatment failure 1
• Distinguish infection from colonization: E. faecalis may be present in vaginal cultures without causing true infection; treat only symptomatic patients 1, 2
• Do not confuse with bacterial vaginosis: E. faecalis vaginal infection requires different treatment than polymicrobial bacterial vaginosis 1
• Avoid cephalosporins as monotherapy: They have minimal activity against enterococci and will fail 2
• Do not use vancomycin empirically: Reserve it for confirmed resistance or severe penicillin allergy to preserve its effectiveness 2
• Aminoglycosides are not needed: Unlike enterococcal endocarditis, uncomplicated vaginal infections do not require synergistic combination therapy with gentamicin 3, 4

Resistance Considerations

• E. faecalis from urogenital sources shows 100% susceptibility to ampicillin and amoxicillin in most studies 5
• Tetracycline, erythromycin, clindamycin, and metronidazole show poor activity and should be avoided 6, 5
• If treatment fails, consider longer duration or higher dosage rather than switching antibiotics immediately, unless resistance is documented 4