Do we prescribe antibiotics for a urine culture with 10,000 to 49,000 CFU/mL of Enterococcus faecalis?

Treatment of Urinary Tract Infection with Enterococcus faecalis at 10,000-49,000 CFU/mL

Asymptomatic bacteriuria with Enterococcus faecalis at 10,000-49,000 CFU/mL should not be treated with antibiotics, as treatment is not indicated for asymptomatic bacteriuria in most clinical scenarios.

Decision Algorithm for Treatment

Step 1: Determine if the patient is symptomatic

• Symptomatic UTI: Dysuria, frequency, urgency, suprapubic pain, hematuria
• Asymptomatic bacteriuria: Positive urine culture without symptoms

Step 2: Assess clinical context

1. If asymptomatic:

   • No treatment indicated in most cases 1
   • Exception: Pregnancy or pre-urologic procedure

2. If symptomatic with uncomplicated UTI:

   • Fosfomycin 3g single dose (FDA-approved for E. faecalis UTI) 2
   • Nitrofurantoin 100mg twice daily for 5 days (if CrCl >60 mL/min) 1
   • Ampicillin 1-2g IV q6h or amoxicillin 500mg PO q8h (for susceptible strains) 1

3. If symptomatic with complicated UTI:

   • Remove indwelling catheter if present 3
   • Ampicillin (preferred for susceptible strains) 3
   • Alternative: Vancomycin (for resistant strains) 3

Important Considerations

Colony Count Interpretation

The colony count of 10,000-49,000 CFU/mL is below the traditional threshold of >100,000 CFU/mL typically used to define significant bacteriuria 3. However, lower counts (>10,000 CFU/mL) may be significant in symptomatic patients, particularly with a pure culture of a uropathogen.

Antibiotic Selection

If treatment is indicated based on symptoms:

1. First-line options:

   • Fosfomycin (single 3g dose) - FDA approved for E. faecalis UTI 2
   • Nitrofurantoin (100mg BID for 5 days) - High activity against E. faecalis 4, 5

2. Alternative options:

   • Ampicillin/amoxicillin (for susceptible strains) 1
   • Ciprofloxacin (if susceptible) - Note increasing resistance rates of 43-47% 6, 7

Resistance Concerns

• E. faecalis has shown high resistance to fluoroquinolones (47% to ciprofloxacin) 7
• Hospital-acquired infections have 18 times higher risk of ciprofloxacin resistance 7
• Nitrofurantoin maintains excellent activity against E. faecalis (100% susceptibility in some studies) 6, 5

Common Pitfalls to Avoid

1. Treating asymptomatic bacteriuria unnecessarily:

   • Leads to antibiotic resistance
   • Increases risk of adverse effects
   • Not recommended by guidelines 1

2. Failing to confirm diagnosis before treatment:

   • Obtain urine culture before initiating therapy 1
   • Ensure pure growth of organism

3. Using fluoroquinolones empirically:

   • High resistance rates (47%) make ciprofloxacin a poor empiric choice 7
   • Reserve for susceptible strains when other options aren't available

4. Not tailoring therapy based on susceptibility:

   • Antimicrobial therapy should be tailored when culture and susceptibility reports become available 3

Follow-up Recommendations

• Clinical response should be assessed within 48-72 hours
• If symptoms persist or recur within 2 weeks, repeat urine culture and select a different antibiotic class 1
• For recurrent infections, consider underlying structural abnormalities 3

Remember that the decision to treat should be based on the presence of symptoms, not solely on the colony count or organism identification.