Treatment of Enterococcus Faecalis Infection in a 44-Year-Old Female
For E. faecalis infection in a 44-year-old female, ampicillin plus gentamicin is the recommended first-line treatment for susceptible strains, while ampicillin plus ceftriaxone is preferred for high-level aminoglycoside-resistant strains or patients with renal impairment. 1
Treatment Algorithm Based on Site of Infection and Susceptibility
Step 1: Determine Site of Infection and Obtain Susceptibility Testing
- Blood cultures with susceptibility testing for:
- Penicillin/ampicillin susceptibility
- Vancomycin susceptibility
- High-level aminoglycoside resistance (HLAR)
- β-lactamase production (rare in E. faecalis)
Step 2: Select Antimicrobial Regimen Based on Site and Susceptibility
For Bloodstream Infections/Endocarditis:
Ampicillin-Susceptible, Non-HLAR Strains:
- First-line: Ampicillin 2g IV every 4 hours + Gentamicin 3 mg/kg/day IV divided every 8 hours 1
- Duration: 4-6 weeks (4 weeks for native valve with symptoms <3 months; 6 weeks for native valve with symptoms >3 months or prosthetic valve) 1
Ampicillin-Susceptible, HLAR Strains:
Ampicillin-Resistant Strains:
Vancomycin-Resistant E. faecalis (VRE):
For Urinary Tract Infections:
- Ampicillin 500 mg PO/IV every 8 hours 1
- For uncomplicated UTI: Nitrofurantoin 100 mg twice daily for 5 days 2
- For ampicillin-resistant VRE UTI: Fosfomycin (FDA approved for E. faecalis UTIs) 1
For Intra-abdominal Infections:
- Tigecycline is recommended as drug of choice for VRE intra-abdominal infections 1
Special Considerations
Monitoring During Treatment
- Monitor renal function when using aminoglycosides
- For gentamicin: Adjust dose to achieve 1-hour serum concentration of ~3 μg/mL and trough <1 μg/mL 1
- Perform transesophageal echocardiography (TEE) if E. faecalis bacteremia persists >72 hours after catheter removal or if clinical signs of endocarditis are present 1
Duration of Therapy
- For uncomplicated infections: 10-14 days after resolution of signs of infection 1
- For complicated infections (endocarditis, septic thrombophlebitis): 4-6 weeks 1
- For osteomyelitis: 6-8 weeks 1
Treatment Pitfalls to Avoid
Failing to recognize HLAR: Always test for high-level aminoglycoside resistance, as aminoglycoside-containing regimens would be ineffective in these cases 1
Inadequate dosing: For serious infections, ensure adequate dosing of ampicillin (2g IV every 4 hours) to achieve bactericidal activity 1
Overlooking endocarditis: E. faecalis has a higher risk of endocarditis than E. faecium; consider TEE in persistent bacteremia 1
Nephrotoxicity risk: Gentamicin-associated nephrotoxicity may significantly complicate a 4-6 week course of therapy, especially in older or debilitated patients 1
Misinterpreting susceptibility: E. faecalis may appear susceptible to cephalosporins in vitro but is intrinsically resistant; avoid cephalosporin monotherapy 1
Recent Evidence and Emerging Approaches
Recent genomic studies have shown that certain genetic lineages of E. faecalis (ST6) may have decreased susceptibility to the ampicillin-ceftriaxone combination, and ampicillin plus daptomycin may be an effective alternative for these strains 3. This highlights the importance of susceptibility testing and monitoring clinical response.
For multidrug-resistant E. faecalis infections, daptomycin at higher doses (8-12 mg/kg/day) has shown efficacy, particularly for serious infections 1, 4. Daptomycin exhibits rapid, concentration-dependent bactericidal activity against gram-positive bacteria, including E. faecalis 4.
By following this treatment algorithm and being aware of potential pitfalls, clinicians can optimize outcomes for patients with E. faecalis infections while minimizing the risk of treatment failure and complications.