Urine culture

• 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

• 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