What is the recommended treatment for an Enterococcus faecalis infection?

Treatment of Enterococcus faecalis Infections

For Enterococcus faecalis infections, ampicillin is the drug of choice for ampicillin-susceptible strains, while vancomycin should be used for ampicillin-resistant strains. 1

First-Line Treatment Options Based on Infection Site

Uncomplicated Infections

• Ampicillin-susceptible E. faecalis:

  • Ampicillin: First-line therapy 1
  • Dosage: 2g IV every 6 hours (for serious infections) 1
  • Alternative: Amoxicillin 500 mg PO/IV every 8 hours (for less severe infections) 1

• Ampicillin-resistant E. faecalis:

  • Vancomycin: 30 mg/kg/day IV in 2 divided doses 1
  • Target trough concentration: 10-20 μg/mL 1

Urinary Tract Infections

For E. faecalis UTIs, several options are available:

• Uncomplicated UTIs:

  • Nitrofurantoin 100 mg PO every 6 hours 1, 2
  • Fosfomycin 3g single dose PO 1, 2
  • Ampicillin or amoxicillin (if susceptible) 1, 2

• Complicated UTIs:

  • Ampicillin (if susceptible) or vancomycin (if resistant) with longer duration of therapy (7-14 days) 2

Catheter-Related Bloodstream Infections

• Remove infected short-term catheters 1
• For long-term catheters:
  • Remove if there is insertion site infection, suppurative thrombophlebitis, sepsis, endocarditis, persistent bacteremia, or metastatic infection 1
  • If catheter is retained, use antibiotic lock therapy in addition to systemic antibiotics 1
• Treatment duration: 7-14 days 1

Endocarditis

For E. faecalis endocarditis, combination therapy is recommended:

• Ampicillin-susceptible strains:

  • Ampicillin + gentamicin (for synergistic effect) 1
  • Gentamicin should be administered for the initial 2 weeks of therapy 1

• Ampicillin-resistant strains:

  • Vancomycin + gentamicin 1

Treatment of Vancomycin-Resistant E. faecalis (VRE)

For VRE infections, the following options are recommended:

1. Linezolid: 600 mg IV or PO every 12 hours 1
2. Daptomycin: 8-12 mg/kg/day, possibly in combination with β-lactams 1
3. Tigecycline: 100 mg IV loading dose, then 50 mg IV every 12 hours (for intra-abdominal infections) 1

Duration of Therapy

• Uncomplicated infections: 7-14 days 1
• Complicated infections: 14 days or longer, based on clinical response 1
• Endocarditis: ≥6 weeks 1

Important Clinical Considerations

Susceptibility Testing

• Always obtain susceptibility testing before initiating definitive therapy 2, 3
• Test for susceptibility to penicillin/ampicillin, vancomycin, and high-level aminoglycoside resistance 1, 2

Synergistic Therapy

• For serious E. faecalis infections, combination therapy with a cell wall-active agent (ampicillin or vancomycin) plus an aminoglycoside provides synergistic killing 1
• For strains with high-level gentamicin resistance, the combination of ampicillin plus ciprofloxacin may be an alternative if the strain is susceptible 4

Monitoring

• For patients with persistent bacteremia (>72 hours after appropriate therapy), consider:
  • Echocardiography to rule out endocarditis 1
  • Removal of any indwelling catheters 1
  • Evaluation for metastatic foci of infection

Pitfalls to Avoid

1. Failing to test for high-level aminoglycoside resistance: Without this testing, synergistic combinations may be ineffective 1, 3

2. Inadequate dosing of ampicillin for serious infections: Higher doses (18-30g daily in divided doses) may be needed for severe infections 1

3. Overlooking the possibility of endocarditis: Consider echocardiography for patients with persistent bacteremia or fever despite appropriate therapy 1

4. Inappropriate empiric therapy for healthcare-associated infections: These often require broader coverage due to higher resistance rates 1

5. Treating asymptomatic bacteriuria: This should be avoided as it contributes to antibiotic resistance without clinical benefit 2

By following these evidence-based recommendations, clinicians can optimize outcomes for patients with E. faecalis infections while minimizing the risk of treatment failure and antimicrobial resistance.