Oral Amoxicillin for E. faecalis Treatment
For confirmed E. faecalis infections, oral amoxicillin monotherapy is NOT recommended as standard treatment—intravenous ampicillin (equivalent to amoxicillin) at 2 g every 4 hours (12 g/24 hours total) combined with either gentamicin or ceftriaxone for 4-6 weeks is the guideline-directed therapy. 1
Standard IV Treatment Regimen (Not Oral)
The established treatment for E. faecalis infections requires intravenous therapy, not oral:
First-Line Combination Therapy
- Ampicillin 2 g IV every 4 hours (12 g/24 hours in 6 divided doses) PLUS gentamicin 3 mg/kg/day IV or IM in 1 dose for 2-6 weeks for aminoglycoside-susceptible strains 2, 1
- Duration depends on infection site: 4 weeks for native valve endocarditis with symptoms <3 months, 6 weeks for symptoms ≥3 months or prosthetic valve involvement 2
Alternative for High-Level Aminoglycoside Resistance (HLAR)
- Ampicillin 2 g IV every 4 hours (12 g/24 hours) PLUS ceftriaxone 2 g IV every 12 hours (4 g/24 hours) for 6 weeks 2, 1, 3
- This combination is effective against E. faecalis strains with and without HLAR and has significantly lower nephrotoxicity (0% vs 23% with aminoglycoside regimens) 3
Limited Role for Oral Therapy
Transition to Oral After Initial IV Treatment
- Oral antibiotic therapy may be considered only in highly selected stable patients with left-sided IE caused by E. faecalis after initial intravenous antibiotics, if TEE shows no paravalvular infection, frequent follow-up is assured, and repeat TEE can be performed 1-3 days before completion 2
- This is a Class IIb recommendation (may be considered), not standard practice 2
Prophylaxis Context Only
- Single-dose oral amoxicillin 2-3 g provides 100% protection in experimental endocarditis prophylaxis models 4
- However, this applies to prophylaxis before procedures, NOT treatment of established infection 4
Critical Monitoring Parameters
- Monitor renal function weekly (twice weekly if using aminoglycosides) by assessing creatinine clearance 2, 1
- Gentamicin levels: target 1-hour serum concentration ≈3 μg/mL and trough <1 μg/mL when using divided dosing 2
- Avoid streptomycin if creatinine clearance <50 mL/min 2
Common Pitfalls and How to Avoid Them
- Never use oral monotherapy for active E. faecalis infection—combination IV therapy is essential for synergistic bactericidal activity 1
- Do not shorten therapy below recommended durations (4-6 weeks depending on clinical scenario) 1
- Always test for high-level aminoglycoside resistance—if present, switch to ampicillin-ceftriaxone combination rather than ampicillin-gentamicin 2, 1
- Administer gentamicin in divided doses (every 8 hours), not once daily, for enterococcal infections despite once-daily dosing being used for other infections 2
- Do not obtain blood cultures after starting antibiotics in patients with known valvular heart disease and unexplained fever 2