Asymptomatic Bacteriuria

[Clin Infect Dis 2005; 40:643-54]


- Asymptomatic bacteriuria (ASB) is a colonization state and does NOT indicate an infection that requires treatment. Pyuria is very common in patients with asymptomatic bacteriuria and is also NOT an indication for antibiotic treatment.

  • asymptomatic females - two consecutive voided urine cultures with ≥ 108 cfu/L of same organism +/- pyuria.

  • asymptomatic males - one voided urine culture with ≥ 108 cfu/L of ≥ 1 organism +/- pyuria.

  • catheterized patients - catheter urine culture with ≥105 cfu/L of ≥ 1 organism +/- pyuria and no symptoms of UTI.

Incidence of asymptomatic bacteriuria:

  • young adults: 1-3%

  • >65 years old: 20% females, 10% males

  • >80 years old: 50% females, 30% males

  • catheterized:

    • intermittent: 38-58%

    • short-term (< 30 days) indwelling: 9-23%

    • long-term (≥ 30 days) indwelling: 100%


- Hospital > nursing home > community

Associated laboratory findings:

- Routine screening cultures not recommended, unless prior to GU surgery or pregnant. NB: cloudy/foul smelling urine alone is not an indication for urine culture.

- Up to 90% of elderly patients with asymptomatic bacteriuria have pyuria, hence pyuria is not a valid diagnostic criterion for UTI in this patient population; clinical correlation required.

Antibiotic therapy:

- NO evidence that antibiotic therapy of asymptomatic bacteriuria decreases symptomatic UTI.

- NO evidence that antibiotic therapy of asymptomatic bacteriuria is of any benefit EXCEPT:

  • prior to genitourinary (GU) procedures in which mucosal bleeding/ trauma is expected, or

  • in pregnancy.

- Inappropriate treatment of ASB is a significant contributor to antimicrobial overuse, antimicrobial resistance, and adverse drug effects including Clostridioides (Clostridium) difficile infection.

- Antibiotic therapy of asymptomatic bacteriuria is specifically NOT recommended:

  • young women with recurrent UTI as it:

    • increases risk of recurrent UTI

    • increases risk of multi-drug resistant E. coli [Clin Infect Dis 2012;55:771-7]

  • renal transplant patients

  • diabetic patients

  • prior to minor urologic procedures (no mucosal bleeding)

  • prior to orthopedic surgery

  • prior to catheter removal

  • patients with long term catheterization

  • patients with spinal cord injury.

- Asymptomatic bacteriuria is NOT associated with incontinence, hypertension, or decreased renal function in the elderly.