Treatment of Enterococcus faecalis Infections
Ampicillin 2 g IV every 4-6 hours is the gold standard first-line therapy for susceptible E. faecalis infections, as most strains retain ampicillin susceptibility. 1, 2
Species Identification is Critical
- E. faecalis and E. faecium require fundamentally different treatment approaches due to intrinsic resistance patterns—never assume they have the same susceptibility profile. 1
- E. faecalis accounts for 80-90% of clinical enterococcal isolates, while E. faecium represents only 5-10%. 3
- Only 3% of E. faecalis strains are multidrug-resistant, and many vancomycin-resistant E. faecalis remain penicillin-susceptible. 1
First-Line Treatment for E. faecalis
Ampicillin-Susceptible Strains
- Ampicillin 2 g IV every 4-6 hours is the preferred agent, with amoxicillin potentially offering lower MICs according to the European Society of Cardiology. 1, 2
- Piperacillin-tazobactam is an effective alternative for polymicrobial infections. 4, 2
Vancomycin-Resistant Strains
- For ampicillin-resistant E. faecalis, vancomycin is the alternative, though the American Heart Association recommends against empirical vancomycin use when ampicillin susceptibility is likely. 1, 2
Combination Therapy for Serious Infections
When Bactericidal Activity is Required
- For endocarditis, combine ampicillin with gentamicin for synergistic bactericidal effect, treating native valve endocarditis for 4-6 weeks and prosthetic valve endocarditis for minimum 6 weeks. 1, 2
- For aminoglycoside-resistant strains, ampicillin plus ceftriaxone is the recommended alternative. 2
- High-level aminoglycoside resistance is present in 38% of enterococcal isolates, limiting traditional synergistic combinations. 1, 5
Non-Endocarditis Infections
- The role of combination therapy for non-endocarditis infections remains unresolved, and monotherapy is typically sufficient. 2
Empiric Coverage Decisions
Community-Acquired Intra-Abdominal Infections
- Empiric enterococcal coverage is NOT necessary for patients with mild-to-moderate community-acquired intra-abdominal infections. 4
Health Care-Associated Infections Requiring Empiric Coverage
- Empiric anti-enterococcal therapy is recommended for: 4
- Postoperative intra-abdominal infections
- Patients who previously received cephalosporins or other agents selecting for Enterococcus
- Immunocompromised patients
- Patients with valvular heart disease or prosthetic intravascular materials
- Initial empiric therapy should target E. faecalis with ampicillin, piperacillin-tazobactam, or vancomycin based on susceptibility patterns. 4
Duration of Therapy
- Uncomplicated infections: 7-14 days 1, 2
- Endocarditis or serious infections: 4-6 weeks minimum 1, 2
- Prosthetic valve endocarditis: 6 weeks minimum 1, 2
- Catheter-related bloodstream infections: 7-14 days after catheter removal 2
Critical Pitfalls to Avoid
- Never use cephalosporins alone for enterococcal coverage—they have no intrinsic activity against enterococci despite potential in vitro synergy when combined with ampicillin. 1, 2
- Do not prescribe vancomycin empirically for suspected E. faecalis when beta-lactam allergy is not documented, as ampicillin is superior. 1
- Always obtain infectious disease consultation for enterococcal endocarditis management as standard of care. 1, 2
- Verify the antibiogram and adjust therapy when culture and sensitivity results become available. 1
- Consider resistance or alternative diagnosis if no clinical improvement occurs after 48-72 hours of appropriate therapy. 1
FDA-Approved Agents
- Daptomycin is FDA-approved for complicated skin and skin structure infections caused by E. faecalis (vancomycin-susceptible isolates only), but is NOT indicated for pneumonia or left-sided endocarditis. 6
- Linezolid is FDA-approved for vancomycin-resistant enterococcal infections, with cure rates of 67% in the high-dose (600 mg q12h) arm versus 52% in the low-dose arm. 7