What antibiotics are used to treat Enterococcus (E) faecium urinary tract infections (UTI)?

Antibiotic Treatment for Enterococcus faecium UTI

For E. faecium urinary tract infections, first-line treatment options include fosfomycin (3g single dose), nitrofurantoin (100mg twice daily for 5 days), or high-dose ampicillin/amoxicillin for susceptible strains, with linezolid or daptomycin reserved for complicated or resistant infections. 1

Treatment Algorithm Based on Infection Severity and Resistance Pattern

Uncomplicated Lower UTI (Cystitis)

• First-line options:
  • Fosfomycin 3g single oral dose 1
  • Nitrofurantoin 100mg twice daily for 5 days 1
  • Ampicillin-susceptible strains: Amoxicillin 500mg every 8 hours 1
• Treatment duration: 5-7 days for uncomplicated infections 1

Complicated UTI or Pyelonephritis

• Parenteral therapy options:
  • Ampicillin-susceptible strains: High-dose ampicillin (18-30g IV daily) 1
  • Vancomycin-resistant E. faecium (VRE):
    • Daptomycin ≥8 mg/kg (up to 10-12 mg/kg) IV daily 1
    • Linezolid 600mg IV/PO every 12 hours 1, 2
• Treatment duration: 10-14 days 1

Considerations for Resistant Strains

Vancomycin-Resistant E. faecium (VRE)

• For uncomplicated lower UTI:

  • Nitrofurantoin and fosfomycin retain activity against most VRE strains 1, 3
  • High urinary concentrations of ampicillin/amoxicillin may still be effective despite in vitro resistance (clinical success rates of 88.1%) 1

• For complicated UTI/pyelonephritis with VRE:

  • Linezolid 600mg every 12 hours (despite limited urinary excretion, clinical data supports efficacy) 2
  • Daptomycin ≥8 mg/kg IV daily 1, 4
  • Consider infectious disease consultation for multidrug-resistant infections 1

Important Clinical Considerations

• Differentiate colonization from true infection: Most patients with E. faecium in urine cultures (64%) represent asymptomatic bacteriuria and do not require treatment 2

• Susceptibility testing: Critical for E. faecium due to high rates of resistance; E. faecium is generally more resistant than E. faecalis 1

• Catheter management: Remove indwelling catheters when possible as part of treatment 4

• Follow-up cultures: Recommended 1-2 weeks after completing therapy if symptoms persist 1

Antibiotic Caveats and Pitfalls

• Cephalosporins: Enterococci have intrinsic resistance to cephalosporins including newer agents like ceftaroline 1

• Fluoroquinolones: High rates of resistance make these unreliable for empiric therapy 1

• Linezolid concerns: Monitor for thrombocytopenia with courses >14 days 5

• Quinupristin/dalfopristin: Limited by side effects (myalgia/arthralgia) and should be reserved for cases with limited options 5, 3

• Tigecycline: Limited data for UTIs and suboptimal pharmacokinetics for severe infections 6

• Aminoglycosides: May be considered as adjunctive therapy in serious infections but not as monotherapy 4

The Infectious Diseases Society of America guidelines emphasize the importance of susceptibility testing to guide therapy, especially for E. faecium which typically has higher resistance rates than E. faecalis 1. For multidrug-resistant strains, infectious disease consultation is strongly recommended 1.