What is the recommended treatment for a patient with a urinary tract infection caused by Enterococcus faecalis, given the results of the urine culture and antimicrobial susceptibility testing?

Treatment for Enterococcus faecalis Urinary Tract Infection

For a urinary tract infection caused by Enterococcus faecalis with the provided susceptibility results, penicillin or nitrofurantoin is the recommended first-line treatment due to demonstrated susceptibility and established clinical efficacy.

Interpretation of Culture Results

The urine culture shows:

• Organism: Enterococcus faecalis
• Colony count: >100,000 CFU/mL (significant bacteriuria)
• Susceptibility profile:
  • Susceptible: Ciprofloxacin, Levofloxacin, Nitrofurantoin, Penicillin, Vancomycin
  • Resistant: Tetracycline

Treatment Algorithm

First-line options (based on susceptibility and guidelines):

1. Uncomplicated UTI (cystitis):

   • Nitrofurantoin 100 mg PO every 6 hours for 5 days 1
   • Penicillin derivatives:
     • Ampicillin 500 mg PO every 8 hours for 5-7 days
     • Amoxicillin 500 mg PO every 8 hours for 5-7 days

2. Complicated UTI or pyelonephritis:

   • Ampicillin 1-2 g IV every 6 hours for 7-14 days
   • Penicillin G 2-4 million units IV every 4-6 hours for 7-14 days

Alternative options (if first-line cannot be used):

• Fluoroquinolones (based on susceptibility):

  • Ciprofloxacin 500 mg PO twice daily for 7 days
  • Levofloxacin 500 mg PO daily for 7 days

• Vancomycin (reserve for serious infections or when other options cannot be used):

  • 15-20 mg/kg IV every 12 hours (adjusted based on renal function)

Rationale for Treatment Selection

1. Penicillin/Ampicillin: Enterococci susceptible to penicillin are predictably susceptible to ampicillin, amoxicillin, and other beta-lactams as noted in the culture report. These are considered first-line therapy for enterococcal infections 1.

2. Nitrofurantoin: Highly effective for uncomplicated UTIs caused by E. faecalis with excellent urinary concentrations and low resistance rates 1, 2. The culture shows susceptibility to nitrofurantoin.

3. Fluoroquinolones: While the organism is susceptible to ciprofloxacin and levofloxacin, these should be reserved as alternatives due to concerns about promoting resistance and ecological adverse effects 1.

Special Considerations

• Avoid cephalosporins, clindamycin, and trimethoprim-sulfamethoxazole: As noted in the culture report, these are not effective against Enterococcus species even if reported as susceptible 1.

• Duration of therapy:

  • Uncomplicated cystitis: 5 days
  • Complicated UTI or pyelonephritis: 7-14 days

• Follow-up: Routine post-treatment urinalysis or urine cultures are not indicated for asymptomatic patients 1. Only repeat cultures if symptoms persist or recur within 2 weeks of treatment completion.

Pitfalls to Avoid

1. Using tetracycline: The isolate is resistant to tetracycline and should not be used.

2. Using aminoglycosides as monotherapy: Enterococci have intrinsic low-level resistance to aminoglycosides, making them ineffective as single agents 1.

3. Treating asymptomatic bacteriuria: Unless the patient is pregnant or undergoing urologic procedures, asymptomatic bacteriuria with enterococci generally does not require treatment 3.

4. Failing to assess for complicated UTI: E. faecalis UTIs are associated with higher rates of anatomical abnormalities, especially in children 4. Consider imaging if recurrent infections occur.

5. Overlooking catheter removal: If a urinary catheter is present, removal or replacement should be considered as part of the management strategy 3.