What antibiotic is recommended for a patient with urinary frequency, urgency, and fever with a positive culture for Enterococcus faecalis?

Treatment of Urinary Tract Infection Caused by Enterococcus faecalis

For urinary tract infection with urinary frequency, urgency, and fever caused by Enterococcus faecalis, ampicillin or amoxicillin is the first-line treatment of choice, with nitrofurantoin as an effective oral alternative for uncomplicated cases.

First-Line Treatment Options

For Uncomplicated UTI:

• Nitrofurantoin 100 mg PO twice daily for 5 days 1
  • High urinary concentrations
  • Low resistance rates among E. faecalis (100% susceptibility reported in some studies) 2, 3
  • Contraindicated if CrCl <30 mL/min or signs of pyelonephritis 1

For Complicated UTI (including fever suggesting pyelonephritis):

• Ampicillin 200 mg/kg/day IV in 4-6 divided doses 4
  • High efficacy against E. faecalis with 96% susceptibility 2
  • For oral step-down therapy: Amoxicillin 500-875 mg three times daily
• Ampicillin-sulbactam (if beta-lactamase production suspected) 4, 5
  • Particularly effective for hospital-acquired infections

Alternative Treatments

For Penicillin-Allergic Patients:

• Vancomycin 30 mg/kg/day IV in 2 doses 4
  • Excellent activity against E. faecalis (nearly 100% susceptibility) 2, 3
  • Monitor serum vancomycin levels

For Oral Step-Down Therapy:

• Fosfomycin 3g single dose (if susceptibility confirmed) 1
• Linezolid 600 mg twice daily (reserve for resistant strains) 3, 6

Treatment Duration

• Uncomplicated lower UTI: 5-7 days 1
• Complicated UTI or pyelonephritis: 10-14 days 1

Special Considerations

For High-Level Aminoglycoside Resistance (HLAR):

• Approximately 17-29% of E. faecalis strains demonstrate HLAR 2
• For these cases, avoid aminoglycoside combination therapy
• Consider ampicillin-ceftriaxone combination for severe infections 4

For Hospital-Acquired Infections:

• Higher risk of ciprofloxacin resistance (OR 18.15) 5
• Avoid fluoroquinolones as empiric therapy
• Consider ampicillin-sulbactam or vancomycin pending susceptibilities 5

Monitoring and Follow-up

• Clinical improvement should be seen within 48-72 hours 1
• Follow-up urine culture if symptoms persist after completing therapy
• Monitor renal function if using aminoglycosides or vancomycin

Important Caveats

• Fluoroquinolones show high resistance rates (43-47% for ciprofloxacin) and are not recommended as first-line therapy 2, 5
• E. faecalis is intrinsically resistant to cephalosporins, which should be avoided 2
• Nitrofurantoin may be ineffective for E. faecium (only 50% susceptibility) but works well for E. faecalis 2
• Antibiotic prophylaxis with nitrofurantoin may increase virulence properties of E. faecalis and is not recommended for recurrent UTIs caused by this organism 7

Treatment Algorithm

1. Assess severity (uncomplicated vs. complicated/pyelonephritis)
2. For uncomplicated lower UTI without fever: Nitrofurantoin 100 mg PO BID for 5 days
3. For complicated UTI or pyelonephritis: Start IV ampicillin or ampicillin-sulbactam
4. Adjust therapy based on susceptibility results
5. Step down to oral therapy when clinically improved