Urine culture

Organism growth

  • Usually indicates UTI in patient with urinary symptoms (higher counts have an even higher predictive value)
    • > 103 CFU/mL – E.coli or S.saprophyticus
    • > 104 CFU/mL – single organism
    • > 105 CFU/mL – mixed growth with one predominant organism

White blood cells

  • >104/mL represent inflammation
  • no white cells present indicates no inflammation and reduces culture significance
  • sterile pyuria
    • consider Chlamydia, other vaginal infections, non culturable organisms (e.g. TB), renal pathology
    • pregnancy is associated with physiological pyuria

Epithelial cells

  • Indicates perineal contamination which reduces significance of a culture

Red cells

  • May be present in UTI
  • Persistent haematuria requires referral
  • Lab microscopy is less accurate than dipstick due to red cell lysis in transport



Urine culture in > 65  years old

  • Do not treat asymptomatic bacteriuria in the elderly as it is common and does not reduce mortality or prevent symptomatic episodes

Urine culture in patients with indwelling catheters

  • Do not treat asymptomatic bacteriuria in these patients
  • If signs of infection
    • exclude other sources
    • check catheter is draining correctly and is not blocked
    • If catheter in place for more than 7 days, consider changing it before/when starting antibiotic treatment