Treatment of Enterococcus faecalis Infections
For susceptible E. faecalis infections, ampicillin 2 g IV every 4-6 hours is the gold standard first-line therapy, with combination therapy reserved for serious infections requiring bactericidal activity. 1, 2
First-Line Treatment by Infection Severity
Uncomplicated Infections (7-14 days)
- Ampicillin 2 g IV every 4-6 hours for hospitalized patients with confirmed susceptibility (MIC ≤8 mg/L) 1, 2
- Amoxicillin 500 mg orally every 8 hours for uncomplicated cystitis 2
- High-dose amoxicillin 1000 mg orally three times daily for outpatient treatment of less severe infections or chronic prostatitis (4-6 weeks for prostatitis) 2
Serious Infections Requiring Bactericidal Activity
For infective endocarditis (IE) with aminoglycoside-susceptible strains:
- Ampicillin 2 g IV every 4 hours PLUS gentamicin for synergistic bactericidal effect 3, 1
- Native valve endocarditis: 4-6 weeks (4 weeks if symptoms <3 months duration, 6 weeks if symptoms >3 months) 3
- Prosthetic valve endocarditis: minimum 6 weeks 3, 1
For aminoglycoside-resistant strains (high-level gentamicin resistance):
- Double β-lactam regimen: Ampicillin 2 g IV every 4 hours PLUS ceftriaxone 2 g IV every 12 hours for 6 weeks 3, 1
- This combination has similar cure rates to aminoglycoside-containing regimens with significantly lower nephrotoxicity risk 3
- Ceftriaxone alone has NO activity against enterococci; it only works synergistically with ampicillin 1, 2
Alternative Regimens for β-Lactam Allergy or Resistance
Vancomycin 30 mg/kg/day IV in 2 divided doses is the primary alternative for severe penicillin allergy or ampicillin-resistant strains 2
- For endocarditis: Vancomycin PLUS gentamicin for 6 weeks (native valve) or minimum 6 weeks (prosthetic valve) 3
- Vancomycin-gentamicin is LESS effective than ampicillin-gentamicin due to higher ototoxicity/nephrotoxicity risk and inferior in vitro/in vivo activity 3
For vancomycin-resistant E. faecalis (VRE):
- Linezolid 600 mg IV/PO every 12 hours is the preferred agent with proven clinical efficacy 1, 2
- Daptomycin 8-12 mg/kg/day IV is an alternative option 1, 2
- Note: Only 3% of E. faecalis strains are multidrug-resistant, and many VRE E. faecalis remain penicillin-susceptible 1
Site-Specific Treatment Considerations
Intra-abdominal infections:
- Piperacillin-tazobactam can be used for polymicrobial infections, then tailor to ampicillin once E. faecalis is confirmed 2
- For community-acquired biliary infections in immunocompetent hosts, anti-enterococcal coverage is NOT required unless the patient is immunosuppressed 2
Genitourinary infections:
- Chronic prostatitis requires high-dose amoxicillin 1000 mg three times daily for 4-6 weeks to overcome the blood-prostate barrier 2
Healthcare-associated infections:
- Anti-enterococcal coverage is mandatory when E. faecalis is recovered from healthcare-associated infections, particularly with prior cephalosporin exposure, prosthetic materials, or valvular heart disease 2, 4
Critical Pitfalls to Avoid
- NEVER use cephalosporins alone for enterococcal coverage—they have no intrinsic activity against enterococci despite in vitro synergy when combined with ampicillin 1, 2
- Do NOT assume E. faecium has the same susceptibility as E. faecalis—E. faecium has intrinsic penicillin resistance and requires vancomycin or newer agents (linezolid/daptomycin) 1
- Avoid streptomycin in patients with creatinine clearance <50 mL/min 3
- Always obtain infectious disease consultation for enterococcal endocarditis as standard of care 3, 1
- Differentiate colonization from true infection before initiating treatment, as antibiotic exposure (especially clindamycin, third-generation cephalosporins, penicillins, fluoroquinolones) promotes enterococcal colonization 4