Do you treat a urine culture with 10,000 to 50,000 Colony-Forming Units per Milliliter (CFU/mL) and Enterococcus faecalis?

Treatment of Urine Culture with 10,000 to 50,000 CFU/mL and Enterococcus faecalis

A urine culture with 10,000 to 50,000 CFU/mL of Enterococcus faecalis generally should not be treated unless the patient has symptoms of UTI and evidence of pyuria.

Diagnostic Interpretation

Colony Count Significance

• According to the American Academy of Pediatrics guidelines, the appropriate threshold to consider bacteriuria "significant" is typically ≥50,000 CFU/mL of a single urinary pathogen 1
• The Infectious Diseases Society of America defines significant bacteriuria differently based on collection method:
  • For catheterized specimens: ≥102 CFU/mL
  • For clean-catch voided specimens: typically ≥105 CFU/mL 1
• Colony counts between 10,000-50,000 CFU/mL fall into a transition range that requires clinical correlation 1

Clinical Correlation is Essential

• The presence of pyuria (≥10 white blood cells/mm³) is critical for distinguishing true UTI from asymptomatic bacteriuria 2
• In a study of catheterized specimens, patients with <10 leukocytes/mm³ showed findings consistent with colonization rather than infection, even with positive cultures 2

Decision Algorithm for Treatment

Step 1: Assess for Symptoms

• Check for presence of:
  • Dysuria
  • Frequency
  • Urgency
  • Fever (particularly important)
  • Suprapubic discomfort

Step 2: Evaluate Urinalysis

• Look for evidence of inflammation:
  • Pyuria (≥10 WBC/mm³)
  • Positive leukocyte esterase
  • Presence of nitrites (though Enterococcus is often nitrite-negative)

Step 3: Consider Patient Risk Factors

• Higher risk of true infection with:
  • Hospitalization (OR=4.4)
  • Urinary symptoms (urgency has OR=7.1) 3
  • Anatomical abnormalities of the urinary tract
  • Advanced age
  • Immunocompromised state

Step 4: Make Treatment Decision

• Treat if:
  • Colony count 10,000-50,000 CFU/mL AND
  • Symptoms present AND
  • Evidence of pyuria
• Do not treat if:
  • Asymptomatic OR
  • No evidence of pyuria

Treatment Considerations

Antibiotic Selection

• If treatment is warranted:
  • Ampicillin is typically effective against Enterococcus faecalis 4
  • Nitrofurantoin is also usually effective 4
  • Base choice on local antimicrobial sensitivity patterns and adjust according to sensitivity testing 1

Duration of Treatment

• 7-14 days is the recommended duration for symptomatic UTI 1

Important Considerations

Enterococcus faecalis Significance

• E. faecalis has been shown to invade urothelial cells and form intracellular reservoirs that may contribute to chronic UTIs 5
• Enterococcal UTIs in children are associated with higher rates of anatomical abnormalities and worse prognosis in terms of renal scarring and recurrences 4

Common Pitfalls

1. Overtreatment of asymptomatic bacteriuria: Treatment of asymptomatic bacteriuria may be harmful and lead to antimicrobial resistance 1, 6
2. Undertreatment of true infections: Low colony counts (10,000-50,000 CFU/mL) with symptoms and pyuria may represent true infections, especially in hospitalized patients 3
3. Ignoring pyuria: The presence of pyuria is crucial for distinguishing true infection from colonization 2

Special Populations

• Pregnant women: Lower thresholds for treatment may apply
• Immunocompromised patients: May have significant bacteriuria without pyuria 6
• Catheterized patients: Different colony count thresholds apply (≥102 CFU/mL) 1

By carefully evaluating both microbiological findings and clinical presentation, clinicians can make appropriate decisions regarding treatment of urine cultures with 10,000 to 50,000 CFU/mL of Enterococcus faecalis, avoiding both unnecessary antibiotic use and missed infections.