What is the recommended treatment for Enterococcus (E.) Faecalis infections?

Treatment of Enterococcus faecalis Infections

Ampicillin is the first-line treatment for most Enterococcus faecalis infections, with specific regimens determined by the site and severity of infection. 1

First-Line Treatment Options

For Uncomplicated Infections

• Ampicillin: 2g IV every 4-6 hours for 7-14 days 1
• Amoxicillin: Oral alternative for less severe infections

For Serious Infections (Endocarditis, Bacteremia)

• Native valve endocarditis: Ampicillin 2g IV every 4 hours for 4-6 weeks 2, 1
  • 4-week therapy for symptoms <3 months
  • 6-week therapy for symptoms >3 months
• Prosthetic valve endocarditis: 6 weeks of therapy required 1

Synergistic Combinations for Serious Infections

• Ampicillin plus gentamicin: Traditional combination for serious infections 2
  • Gentamicin 3 mg/kg per 24h IV in 3 divided doses
  • Duration: 4-6 weeks for endocarditis

Alternative Regimen for Aminoglycoside-Resistant Strains

Double β-Lactam Regimen

• Ampicillin plus ceftriaxone: Recommended for high-level aminoglycoside-resistant strains 2
  • Avoids nephrotoxicity associated with aminoglycosides
  • Particularly beneficial in elderly patients or those with renal impairment

Treatment for Penicillin-Allergic Patients

• Vancomycin: 30 mg/kg per 24h IV in 2 equally divided doses 2, 1
  • Adjust to maintain serum trough concentration of 10-20 μg/mL
  • May be combined with gentamicin if the strain is susceptible

Special Considerations

High-Level Aminoglycoside Resistance

• Test enterococci routinely for high-level resistance to gentamicin (MIC >500 μg/mL) 2
• If high-level resistance is present, aminoglycosides should not be used 1
• Use double β-lactam therapy (ampicillin plus ceftriaxone) instead 2

Renal Function Concerns

• Patients with advanced age or pre-existing renal impairment should avoid aminoglycoside-containing regimens 1
• Monitor renal function regularly during treatment, especially with aminoglycosides

Multidrug-Resistant Strains

• For vancomycin-resistant E. faecalis:
  • Linezolid or daptomycin may be effective 2, 3
  • Daptomycin has shown activity against vancomycin-resistant enterococci 3

Treatment Duration by Infection Type

• Simple UTI: 5-7 days 1
• Complicated UTI/Pyelonephritis: 10-14 days 1
• Bacteremia without endocarditis: 10-14 days after resolution of signs 1
• Endocarditis: 4-6 weeks 2, 1

Monitoring Response

• Assess clinical response within 48-72 hours of starting treatment 1
• For endocarditis, repeat blood cultures to confirm clearance of bacteremia 1
• Regular monitoring of renal function is essential, especially with aminoglycoside therapy 1

Treatment Algorithm

1. Identify site and severity of infection
2. Test for antimicrobial susceptibility, including high-level aminoglycoside resistance
3. For uncomplicated infections: Use ampicillin monotherapy
4. For serious infections:
   • If aminoglycoside-susceptible: Consider ampicillin plus gentamicin
   • If high-level aminoglycoside resistance: Use ampicillin plus ceftriaxone
   • If penicillin-allergic: Use vancomycin (± gentamicin if susceptible)
5. For multidrug-resistant strains: Consider daptomycin or linezolid
6. Monitor clinical response and adjust therapy as needed

Remember that E. faecalis has intrinsic resistance to many antibiotics, including most cephalosporins, which makes treatment challenging and often necessitates combination therapy for serious infections 4.