What is the appropriate treatment for an Enterococcus faecalis urinary tract infection?

Treatment of Enterococcus faecalis UTI

Amoxicillin 500 mg orally every 8 hours for 7 days is the first-line treatment for uncomplicated E. faecalis UTI, achieving 88.1% clinical and 86% microbiological eradication rates. 1

First-Line Treatment: Ampicillin/Amoxicillin

• Ampicillin and amoxicillin remain the drugs of choice for enterococcal UTIs, even when in vitro testing suggests resistance, because high urinary concentrations can overcome elevated MICs 1
• For hospitalized patients requiring IV therapy, use high-dose ampicillin 18-30 g IV daily in divided doses or amoxicillin 500 mg IV every 8 hours 1
• Ampicillin is FDA-approved for E. faecalis genitourinary tract infections (β-lactamase-negative isolates only) 2
• For β-lactamase producing strains, substitute amoxicillin-clavulanate for 7 days 1

Alternative Oral Agents

• Nitrofurantoin 100 mg orally every 6 hours for 7 days is an effective alternative with resistance rates below 6% in E. faecalis 1, 3, 4
• Fosfomycin 3 g orally as a single dose is FDA-approved specifically for E. faecalis UTI and recommended for uncomplicated infections 1
• Fosfomycin has minimal resistance and low collateral damage, though slightly inferior efficacy compared to 7-day regimens 1

Critical Treatment Duration Considerations

• For uncomplicated cystitis: 7 days of therapy 1
• For male patients or when prostatitis cannot be excluded: 14 days (all male UTIs are considered complicated) 5
• For complicated UTI with upper tract involvement or systemic symptoms: 10-14 days 1
• Extend duration if complicating factors present, including urinary retention, fever >37.8°C, rigors, or costovertebral angle tenderness 1

Agents to AVOID

• Fluoroquinolones (ciprofloxacin, levofloxacin) should NOT be used due to high resistance rates of 46-47% in E. faecalis 1, 6
• Ciprofloxacin resistance is particularly high in hospital-acquired infections, patients treated in urology departments, and those transferred from healthcare centers 6
• Cephalosporins are completely ineffective due to natural resistance of all enterococci to cephalosporins 1

Critical Limitations of Nitrofurantoin

• Do NOT use nitrofurantoin for complicated UTI, pyelonephritis, or any systemic enterococcal infection (bacteremia, endocarditis, intra-abdominal infections) due to poor tissue and serum concentrations 1
• Contraindicated in patients with creatinine clearance <60 mL/min as urinary concentrations become inadequate 1

Treatment for Vancomycin-Resistant E. faecalis (VRE)

• Ampicillin/amoxicillin remains effective for VRE UTI due to high urinary concentrations that overcome resistance 1
• For severe VRE UTI with bacteremia: daptomycin 8-12 mg/kg/day IV 1, 7
• Linezolid should be reserved for confirmed or suspected upper tract/bacteremic VRE UTIs among ampicillin-resistant strains 1
• Vancomycin has no oral formulation achieving adequate urinary concentrations and is reserved for IV use in serious systemic infections 1

Essential Clinical Algorithm

Step 1: Obtain urine culture and susceptibility testing before initiating therapy - mandatory even for "pansensitive" strains as resistance patterns vary significantly by institution 1, 5

Step 2: Differentiate colonization from true infection - look for dysuria, frequency, urgency, fever, flank pain, or systemic symptoms; asymptomatic bacteriuria does not require treatment 1, 5

Step 3: Classify infection severity:

• Mild-moderate symptoms: Start amoxicillin 500 mg PO every 8 hours 1, 5
• Severe symptoms or hospitalized: Start ampicillin 2 g IV every 4 hours or amoxicillin plus aminoglycoside IV, transition to oral when afebrile ≥48 hours 5

Step 4: Determine treatment duration:

• Female with uncomplicated cystitis: 7 days 1
• Male patient (any UTI): 14 days 5
• Upper tract involvement or systemic symptoms: 10-14 days 1

Common Pitfalls to Avoid

• Do not empirically use fluoroquinolones - resistance rates are unacceptably high 1, 6
• Do not use nitrofurantoin for complicated UTI, pyelonephritis, or renal impairment 1
• Do not treat asymptomatic bacteriuria with E. faecalis 1, 8
• Do not assume susceptibility without testing - always confirm with culture results 1, 5
• In elderly patients, watch for atypical presentations (delirium rather than dysuria) - urine dipstick specificity is only 20-70% in this population 1