Treatment of Enterococcus faecium Infections

General Treatment Principles

The Infectious Diseases Society of America recommends using ampicillin, piperacillin-tazobactam, or vancomycin for vancomycin-susceptible E. faecium, based on individual isolate susceptibility testing, with a preference for ampicillin or piperacillin-tazobactam if susceptible 1, 2, 3
For vancomycin-resistant E. faecium, linezolid 600 mg IV/PO every 12 hours is the first-line treatment, with high-dose daptomycin plus a β-lactam as the preferred alternative for bacteremia or endocarditis, as recommended by the European Society of Clinical Microbiology and Infectious Diseases 1, 2, 3

For uncomplicated urinary tract infections, fosfomycin 3 g PO single dose, nitrofurantoin 100 mg PO every 6 hours, or high-dose ampicillin 18-30 g IV daily in divided doses are alternative options, as suggested by the Infectious Diseases Society of America 1, 2
For intra-abdominal infections, tigecycline 100 mg IV loading dose then 50 mg IV every 12 hours or linezolid 600 mg IV/PO every 12 hours are recommended, based on clinical response, as per the European Society of Clinical Microbiology and Infectious Diseases 1, 2
For endocarditis, ampicillin 200 mg/kg/day IV in 4-6 doses plus ceftriaxone 4 g/day IV in 2 doses for 6 weeks is recommended for beta-lactam and gentamicin susceptible strains, as suggested by the European Society of Cardiology 6
For multiresistant VRE faecium endocarditis, daptomycin 10 mg/kg/day plus ampicillin 200 mg/kg/day IV in 4-6 doses, linezolid 600 mg IV/PO every 12 hours for ≥8 weeks, or quinupristin-dalfopristin 7.5 mg/kg IV every 8 hours for ≥8 weeks are recommended, as per the European Society of Clinical Microbiology and Infectious Diseases 6

Monitor for daptomycin resistance development during therapy by obtaining repeat cultures if clinical response is inadequate, as recommended by the Infectious Diseases Society of America 3
Standard daptomycin doses (6 mg/kg/day) are inadequate for VRE faecium; higher doses (10-12 mg/kg/day) are required, as suggested by the European Society of Clinical Microbiology and Infectious Diseases 3
Monitor CPK levels at least weekly with daptomycin therapy due to skeletal muscle toxicity risk, as per the European Society of Cardiology 6
Monitor complete blood counts weekly with linezolid due to bone marrow suppression risk, particularly with courses >14-21 days, as recommended by the Infectious Diseases Society of America 1, 2
Source control is critical for treatment success; failure to remove infected devices or drain abscesses will result in treatment failure regardless of antimicrobial choice, as emphasized by the Infectious Diseases Society of America 3