What is the recommended treatment for a patient suspected of having an Enterococcus faecalis infection, particularly in a healthcare setting or with a history that suggests increased susceptibility?

Treatment of Enterococcus faecalis Infection

For suspected Enterococcus faecalis infection, ampicillin 2 g IV every 4-6 hours is the first-line treatment, with vancomycin reserved only for documented beta-lactam allergy or ampicillin-resistant isolates. 1

Initial Empiric Therapy Decision Algorithm

Healthcare-associated vs. community-acquired context determines empiric coverage:

• Healthcare-associated infections (postoperative, prior cephalosporin/antibiotic exposure, immunocompromised, valvular heart disease, prosthetic intravascular materials) require empiric anti-enterococcal therapy 2

• Community-acquired infections in immunocompetent patients without the above risk factors do not routinely require empiric enterococcal coverage 2

• For healthcare-associated intra-abdominal infections specifically, empiric regimens should include piperacillin-tazobactam, ampicillin, or vancomycin based on local susceptibility patterns 2

Definitive Therapy Based on Culture Results

Once E. faecalis is isolated, treatment selection follows this hierarchy:

First-Line: Ampicillin-Susceptible E. faecalis

• Ampicillin 2 g IV every 4-6 hours is the gold standard, as 96% of E. faecalis strains retain ampicillin susceptibility 1, 3
• Amoxicillin may be preferred over ampicillin due to lower MICs, though both are acceptable 1
• Only 3% of E. faecalis strains are multidrug-resistant 1

For Serious/Complicated Infections Requiring Bactericidal Activity

• Ampicillin 2 g IV every 4-6 hours PLUS gentamicin for synergistic bactericidal effect 1
• This combination is specifically indicated for endocarditis, persistent bacteremia, or septic shock 2, 1
• Critical caveat: 17-38% of E. faecalis demonstrate high-level aminoglycoside resistance (HLAR), which eliminates synergy 4, 3, 5
• For HLAR strains with endocarditis, the double β-lactam regimen (ampicillin plus ceftriaxone) is reasonable 1

Second-Line: Ampicillin-Resistant or Beta-Lactam Allergy

• Vancomycin is appropriate for ampicillin-resistant isolates or documented beta-lactam allergy 2, 1
• Do NOT use vancomycin empirically for suspected E. faecalis when ampicillin is an option, as ampicillin is superior 1
• Vancomycin resistance in E. faecalis remains rare (only 2 resistant isolates identified in large surveillance studies) 4

Third-Line: Vancomycin-Resistant E. faecalis (VRE)

• Linezolid 600 mg IV/PO every 12 hours is first-line for VRE 2, 6
• Daptomycin 8-12 mg/kg/day IV is an alternative 2, 6
• Many vancomycin-resistant E. faecalis remain penicillin-susceptible, so verify susceptibility testing 1

Site-Specific Considerations

Catheter-Related Bloodstream Infection (CRBSI)

• Remove short-term catheters immediately 2
• For long-term catheters: remove if insertion site infection, suppurative thrombophlebitis, sepsis, endocarditis, persistent bacteremia >72 hours, or metastatic infection 2
• If catheter retained: add antibiotic lock therapy to systemic treatment 2
• Obtain TEE if new murmur, embolic phenomena, prolonged bacteremia/fever >72 hours despite appropriate therapy, or prosthetic valve present 2

Intra-Abdominal Infection

• For uncomplicated acute cholecystitis/appendicitis: discontinue antibiotics within 24 hours post-operatively if no evidence of infection outside organ wall 2
• For complicated intra-abdominal infections with adequate source control: 3-5 days post-operative therapy is sufficient 2
• Piperacillin-tazobactam provides both anti-enterococcal and polymicrobial coverage for intra-abdominal sources 2

Duration of Therapy

Treatment duration is infection-specific:

• Uncomplicated infections: 7-14 days 2, 1
• CRBSI with catheter removal: 7-14 days 2
• Native valve endocarditis: 4-6 weeks 1
• Prosthetic valve endocarditis: minimum 6 weeks 1
• Persistent bacteremia (>4 days): independently associated with mortality, requires extended therapy and source control evaluation 2

Critical Pitfalls to Avoid

• Never use cephalosporins for enterococcal coverage - they have no intrinsic activity against enterococci despite potential in vitro synergy 1
• Do not assume aminoglycoside synergy works - test for high-level aminoglycoside resistance before relying on combination therapy 4, 3, 5
• Avoid empiric vancomycin for suspected E. faecalis - ampicillin is superior and vancomycin should be reserved for documented resistance or allergy 1
• Do not confuse E. faecalis with E. faecium - E. faecium has intrinsic penicillin resistance and requires different empiric coverage 1, 6
• Always obtain infectious disease consultation for enterococcal endocarditis - this is standard of care 1

Monitoring and Reassessment

• Verify antibiogram when culture results available and adjust therapy accordingly 1
• Reassess at 48-72 hours - if no clinical improvement, consider resistance or alternative diagnosis 1
• For retained catheters with CRBSI: obtain follow-up blood cultures and remove catheter if persistent bacteremia >72 hours after appropriate antibiotic initiation 2