What is the recommended treatment for a patient with an Enterococcus faecalis urinary tract infection (UTI)?

Treatment of Enterococcus faecalis UTI

For uncomplicated E. faecalis UTI, treat with amoxicillin 500 mg orally every 8 hours for 7 days as first-line therapy, achieving 88.1% clinical cure and 86% microbiological eradication rates. 1, 2

Treatment Algorithm by Clinical Scenario

Uncomplicated UTI (Outpatient, Lower Tract)

First-line options:

• Amoxicillin 500 mg orally every 8 hours for 7 days - preferred agent per American College of Physicians 1, 2
• Ampicillin 500 mg orally every 8 hours for 7 days - equivalent alternative 1, 2
• Fosfomycin 3 g orally as single dose - FDA-approved specifically for E. faecalis UTI, convenient for uncomplicated infections 1, 2

Alternative for penicillin allergy:

• Nitrofurantoin 100 mg orally every 6 hours for 7 days - resistance rates below 6%, good in vitro activity 1, 2

Complicated UTI or Pyelonephritis (Hospitalized, IV Therapy Required)

First-line IV therapy:

• High-dose ampicillin 18-30 g IV daily in divided doses (or amoxicillin 500 mg IV every 8 hours) - achieves sufficient urinary concentrations to overcome even high MICs 1, 2

Alternative IV agents for complicated UTI:

• Linezolid 600 mg IV every 12 hours for 5-7 days - strongly recommended 2
• Daptomycin 6-12 mg/kg IV daily for 5-7 days 2

Vancomycin-Resistant E. faecalis (VRE)

For uncomplicated VRE UTI:

• Fosfomycin 3 g orally single dose or every other day 2
• Nitrofurantoin 100 mg orally four times daily for 3-7 days 2
• High-dose ampicillin 18-30 g/day IV in divided doses - recommended despite in vitro resistance because urinary concentrations overcome elevated MICs 1, 2

For complicated VRE UTI with bacteremia:

• Daptomycin 8-12 mg/kg/day IV 1
• Linezolid - reserved for confirmed or suspected upper tract/bacteremic VRE among ampicillin-resistant strains per Infectious Diseases Society of America 1

Critical Clinical Considerations

Always obtain susceptibility testing before initiating therapy, even for strains described as "pansensitive," as resistance patterns vary significantly by institution 1, 2

Differentiate colonization from true infection - asymptomatic bacteriuria with E. faecalis does not routinely require treatment 1

Avoid fluoroquinolones - ciprofloxacin/levofloxacin resistance rates are 46-47%, making them inappropriate choices 1, 3

For beta-lactamase producing strains, replace amoxicillin with amoxicillin-clavulanate for 7 days 1

Important Contraindications and Limitations

Nitrofurantoin restrictions:

• Do NOT use for complicated UTI or pyelonephritis - achieves poor tissue and serum concentrations 1
• Do NOT use for systemic enterococcal infections (bacteremia, endocarditis, intra-abdominal infections) 1
• Contraindicated if creatinine clearance <60 mL/min - urinary concentrations become inadequate 1

Cephalosporins should be avoided - E. faecalis has natural resistance to all cephalosporins per European Society of Cardiology 1

Treatment Duration

• Uncomplicated lower UTI: 7 days 1, 2
• Complicated UTI: 5-7 days 2
• Pyelonephritis: 7-14 days 2
• Duration should be based on clinical response, site of infection, and underlying comorbidities 1, 2