What is the recommended treatment for Enterococcus faecium (E faecium) bacteremia?

Treatment of Enterococcus faecium Bacteremia

For Enterococcus faecium bacteremia, linezolid 600 mg IV or PO every 12 hours is strongly recommended as first-line therapy, while high-dose daptomycin (8-12 mg/kg/day) or daptomycin in combination with beta-lactams is recommended as an alternative option. 1

Treatment Algorithm Based on Resistance Patterns

1. Vancomycin-Susceptible E. faecium

• First-line therapy:

  • Ampicillin 2 g IV every 4 hours (if susceptible) plus gentamicin 3 mg/kg/day IV divided in 3 doses 1
  • Duration: 4-6 weeks for endocarditis; 2 weeks for uncomplicated bacteremia

• For penicillin-allergic patients:

  • Vancomycin 30 mg/kg/day IV in 2 divided doses (adjusted to achieve trough levels of 10-20 μg/mL) plus gentamicin 1

2. Vancomycin-Resistant E. faecium (VRE)

• First-line therapy:

  • Linezolid 600 mg IV or PO every 12 hours (strong recommendation, low quality evidence) 1
  • Duration: Based on clinical response and site of infection

• Alternative therapy:

  • High-dose daptomycin 8-12 mg/kg/day IV (weak recommendation, low quality evidence) 1
  • Consider combination with beta-lactams (ampicillin, ceftaroline) for synergistic effect, especially with persistent bacteremia 1

Special Considerations

Source Control

• Catheter-related infections: Remove infected catheters when possible 1
• Endovascular infections: Evaluate for endocarditis with echocardiography, especially with persistent bacteremia 1
• Intra-abdominal infections: Surgical drainage of abscesses or infected collections is critical for cure 1

Duration of Therapy

• Uncomplicated bacteremia: 7-14 days
• Endocarditis: Minimum 6 weeks
• With metastatic foci: Extended therapy based on clinical response and source control

Evidence Comparison and Limitations

Linezolid has several advantages over daptomycin for VRE bacteremia:

• FDA-approved for VRE infections 2
• Available in both IV and oral formulations
• Better clinical outcomes in meta-analyses (mortality OR: 1.43,95% CI: 1.09-1.86, favoring linezolid over daptomycin) 3
• High microbiological cure rates (86.4%) and clinical cure rates (81.4%) 1

However, daptomycin has theoretical advantages:

• Bactericidal (vs. bacteriostatic for linezolid)
• May be preferred in high-inoculum infections
• Combination with beta-lactams may overcome resistance 1

Monitoring and Adverse Effects

Linezolid

• Monitor for myelosuppression (thrombocytopenia, especially with treatment >14 days) 4
• Watch for peripheral/optic neuropathy with prolonged use
• Serotonin syndrome risk with concomitant serotonergic medications

Daptomycin

• Monitor CPK weekly (risk of myopathy)
• Higher doses (10-12 mg/kg) recommended for VRE bacteremia 1
• Potential for treatment failure in high-inoculum infections

Emerging Approaches

For multidrug-resistant E. faecium (resistant to daptomycin, linezolid, and vancomycin):

• Consider consultation with infectious disease specialists 1
• Novel approaches such as bacteriophage therapy may be considered in refractory cases 5
• Combination therapies may be necessary based on susceptibility testing 6

Common Pitfalls to Avoid

1. Inadequate source control - Failure to remove infected catheters or drain abscesses
2. Insufficient daptomycin dosing - Using standard doses (6 mg/kg) rather than higher doses (10-12 mg/kg) for VRE bacteremia
3. Overlooking endocarditis - Failure to evaluate for endovascular infection in persistent bacteremia
4. Inadequate duration of therapy - Treating complicated infections with short courses
5. Monotherapy for polymicrobial infections - Failing to provide adequate coverage for concomitant gram-negative pathogens

The evidence strongly supports linezolid as first-line therapy for VRE bacteremia, with high-dose daptomycin (alone or in combination) as a reasonable alternative. Source control remains a critical component of successful treatment.