What antibiotics are used to treat Enterococcus faecalis infections?

Antibiotics for Treating Enterococcus faecalis Infections

For Enterococcus faecalis infections, ampicillin is the first-line antibiotic treatment, with combination therapy often required depending on the infection site and severity. 1

First-Line Treatment Options

Penicillin-Susceptible E. faecalis

• Ampicillin: 2g IV every 4 hours (first choice) 2, 1
• Aqueous crystalline penicillin G: 24 million units/24h IV continuously or in 6 equally divided doses 2

Combination Therapy Based on Susceptibility

1. Ampicillin + Gentamicin: For synergistic bactericidal activity

   • Gentamicin: 3 mg/kg/day IV/IM in 3 divided doses 2, 1
   • Target gentamicin levels: 1-hour concentration ~3 μg/mL, trough <1 μg/mL 1

2. Ampicillin + Ceftriaxone: For strains with high-level aminoglycoside resistance

   • Ceftriaxone: 2g IV every 12 hours 2
   • This double β-lactam regimen avoids aminoglycoside toxicity 2, 1

3. Ampicillin + Streptomycin: For gentamicin-resistant strains

   • Streptomycin: 15 mg/kg/day IV/IM in 2 divided doses 2
   • Target streptomycin levels: 1-hour concentration 20-35 μg/mL, trough <10 μg/mL 2

Alternative Treatments for Resistant Strains

Penicillin-Resistant E. faecalis

• Vancomycin: 30 mg/kg/day IV in 2 divided doses 2
  • Plus gentamicin or streptomycin for synergistic effect
  • Target vancomycin trough: 10-20 μg/mL 2

Vancomycin-Resistant E. faecalis (VRE)

1. Linezolid: 600 mg IV/oral every 12 hours 2, 3, 4

   • Effective against both E. faecalis and E. faecium
   • Monitor for thrombocytopenia with prolonged use (>14 days) 3

2. Daptomycin: 8-12 mg/kg/day IV once daily 1, 5, 3

   • Higher doses recommended for serious enterococcal infections 1
   • Monitor weekly creatine kinase levels 1, 5
   • Consider combination with ampicillin for synergistic effect 5

3. Teicoplanin: Effective against some vancomycin-resistant strains 4, 6

   • Not available in the United States

Treatment Duration

• Uncomplicated infections: 7-14 days 1
• Bloodstream infections with central venous catheters: 10-14 days 1
• Endocarditis:
  • Native valve: 4 weeks if symptoms <3 months; 6 weeks if symptoms >3 months 2
  • Prosthetic valve: Minimum 6 weeks 2, 1

Special Considerations

β-lactamase-Producing Strains

• Ampicillin-sulbactam: 3g IV every 6 hours 2
• These strains are rare but should be tested for when treatment fails 2

Intrinsic Resistance Patterns

• E. faecalis is intrinsically resistant to:
  • Cephalosporins (monotherapy) 2, 1
  • Trimethoprim-sulfamethoxazole
  • Clindamycin
  • Aminoglycosides (low-level resistance)

Monitoring Recommendations

• Weekly renal function tests with aminoglycoside therapy 1
• Weekly complete blood counts with linezolid therapy 3
• Weekly CK levels with daptomycin therapy 1, 5
• Follow-up blood cultures to ensure clearance of bacteremia 1

Catheter Management

• Remove infected catheters immediately for enterococcal bloodstream infections 1
• New catheter placement should only occur after blood cultures clear 1

Common Pitfalls

1. Using cephalosporins as monotherapy (intrinsic resistance) 2, 1
2. Failing to test for high-level aminoglycoside resistance before combination therapy 2
3. Inadequate duration of therapy, especially for endocarditis 2, 1
4. Not removing infected catheters, leading to persistent bacteremia 1
5. Inadequate dosing of daptomycin for serious enterococcal infections 1, 3

For serious or complicated enterococcal infections, especially endocarditis or VRE infections, infectious disease consultation is strongly recommended to guide optimal therapy 2, 1.