Effective Antibiotics for Enterococcus faecalis Infections
Ampicillin is the drug of choice for Enterococcus faecalis infections, often combined with gentamicin or ceftriaxone for synergistic effect, while vancomycin, linezolid, and daptomycin are effective alternatives for resistant strains. 1
First-Line Treatment Options
Beta-Lactams
- Ampicillin is the drug of choice for enterococcal infections, including E. faecalis, when the organism is susceptible 1
- High-dose ampicillin (18-30g IV daily) or amoxicillin (500mg PO/IV every 8h) is recommended to achieve sufficient therapeutic concentrations 1
- For serious infections like endocarditis, ampicillin 2g IV every 4 hours is the standard dosing regimen 1
Synergistic Combinations
- Ampicillin plus gentamicin provides synergistic bactericidal effect against E. faecalis 2
- Double beta-lactam therapy (ampicillin plus ceftriaxone) is now preferred for E. faecalis endocarditis, particularly in patients with renal dysfunction or high-level aminoglycoside resistance 3
- The recommended double beta-lactam regimen is ampicillin 2g IV every 4 hours PLUS ceftriaxone 2g IV every 12 hours for 6 weeks 3
Alternative Options for Resistant Strains
Glycopeptides
- Vancomycin is effective against E. faecalis and shows low resistance rates 1, 4
- Recommended dosing is vancomycin 30 mg/kg per 24h IV in 2 equally divided doses 1
- Vancomycin plus gentamicin is recommended for penicillin-resistant E. faecalis 1
Oxazolidinones and Lipopeptides
- Linezolid shows excellent activity against E. faecalis, including vancomycin-resistant strains 1, 4
- Daptomycin is preferred for serious vancomycin-resistant E. faecalis infections at dosing of at least 8 mg/kg and up to 10-12 mg/kg 1, 5
- Daptomycin exhibits rapid, concentration-dependent bactericidal activity against gram-positive bacteria including E. faecalis 5
Urinary Tract Infections
- Fosfomycin is FDA approved for UTIs caused by E. faecalis 1
- Nitrofurantoin has good in vitro activity against E. faecalis, including vancomycin-resistant strains 1, 4
- High urinary concentrations of ampicillin may overcome high MICs of ampicillin-resistant E. faecalis in UTIs 1
Site-Specific Considerations
Endocarditis
- For E. faecalis endocarditis, treatment duration should be 4-6 weeks 1, 6
- Double beta-lactam therapy (ampicillin plus ceftriaxone) has comparable efficacy to ampicillin-gentamicin with less nephrotoxicity 3, 7
- Daptomycin plus ampicillin may be effective against E. faecalis isolates with decreased susceptibility to ampicillin-ceftriaxone 7
Intra-abdominal Infections
- Tigecycline is recommended for intra-abdominal infections caused by vancomycin-resistant enterococci 1
Clinical Pearls and Pitfalls
- Always differentiate colonization from true infection before initiating anti-enterococcal therapy 1
- E. faecalis and E. faecium have different resistance patterns; E. faecalis is generally more susceptible to ampicillin and less likely to be multidrug-resistant 1
- Only about 3% of E. faecalis strains are multidrug-resistant, compared to up to 95% of E. faecium strains 1
- Ceftaroline and most cephalosporins have poor activity against enterococci and should not be used as monotherapy 1
- Combination therapy is generally required for serious E. faecalis infections due to partial resistance to many antimicrobial agents 6
Emerging Options
- Teicoplanin shows excellent activity against E. faecalis with low resistance rates 4
- Eravacycline has in vitro activity against vancomycin-resistant enterococci but clinical evidence for its use is limited 1
- Outpatient parenteral antimicrobial therapy with ampicillin plus once-daily ceftriaxone (4g) may be effective for continuation therapy of E. faecalis endocarditis 8