What to do if urinalysis (UA) shows bacteria but urine culture shows no growth?

Management of Bacteria on UA with Negative Urine Culture

When urinalysis shows bacteria but urine culture shows no growth, no treatment is indicated as this finding alone does not represent a true urinary tract infection requiring antibiotics. 1

Understanding the Discrepancy

The discrepancy between bacteria on urinalysis and negative culture can occur for several reasons:

1. Asymptomatic bacteriuria: Bacterial colonization without true infection
2. Pre-analytical factors: Improper collection, storage, or transport of specimens
3. Prior antibiotic use: May inhibit bacterial growth in culture
4. Fastidious organisms: Some bacteria may not grow on standard culture media

Clinical Decision Algorithm

Step 1: Assess for Symptoms

• If asymptomatic: No treatment needed 1
  • Asymptomatic bacteriuria should not be treated except in:
    • Pregnant women
    • Prior to urological procedures breaching mucosa

Step 2: Evaluate Urinalysis Results

• Bacteria without pyuria: Likely represents contamination or colonization 1, 2
• Bacteria with pyuria (≥10 WBC/hpf): May suggest infection despite negative culture 2
  • Consider repeat testing if symptoms present

Step 3: Consider Patient-Specific Factors

• Neurogenic bladder patients: Avoid surveillance cultures and treatment of asymptomatic bacteriuria 1
• Catheterized patients: Bacteriuria is common (5-10% daily risk) but should not be treated unless symptomatic 1

Important Caveats

• True UTI diagnosis requires:

  • Positive culture (≥50,000 CFU/mL of a uropathogen)
  • Pyuria (≥10 WBC/hpf)
  • Relevant clinical symptoms 2

• Diagnostic accuracy:

  • Nitrites are highly specific (98%) but less sensitive (53%) for UTI 2
  • Combined leukocyte esterase and nitrite testing provides best screening accuracy (sensitivity 93%, specificity 72%) 2

Common Pitfalls to Avoid

1. Overtreatment: Treating asymptomatic bacteriuria leads to:

   • Increased antibiotic resistance
   • Eradication of potentially protective bacterial strains 1
   • Unnecessary side effects

2. Misinterpreting contamination: Bacteria on UA without pyuria often represents contamination, especially with improper collection technique 3

3. Ignoring clinical context: Laboratory findings must be interpreted in the context of the patient's symptoms 3, 4

Special Populations

• Pregnant women: Screen for and treat asymptomatic bacteriuria 1
• Before urological procedures: Screen for and treat asymptomatic bacteriuria 1
• Long-term care residents: Avoid routine screening for asymptomatic bacteriuria 2

By following these evidence-based guidelines, unnecessary antibiotic use can be avoided while ensuring appropriate treatment for true urinary tract infections.