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Approach to the adult with asymptomatic bacteriuria

Thomas Fekete, MD
Thomas M Hooton, MD
Section Editor
Stephen B Calderwood, MD
Deputy Editor
Allyson Bloom, MD


Asymptomatic bacteriuria is defined as isolation of a specified quantitative count of bacteria in an appropriately collected urine specimen from an individual without symptoms or signs of urinary tract infection. This topic will outline the epidemiology, pathophysiology, clinical definitions, and approach to management in specific clinical circumstances.


Urine is normally sterile but can be a good growth medium for bacteria that enter the bladder and are not eliminated. Because of the difficulty in obtaining uncontaminated voided midstream urine specimens, quantitative thresholds have been established to distinguish bladder bacteriuria from urethral contamination. Asymptomatic bacteriuria is defined as isolation of a specified quantitative count of bacteria in an appropriately collected urine specimen from an individual without symptoms or signs of urinary tract infection. The quantitative thresholds are different for voided clean catch specimens and catheterized specimens.

The presence of pyuria (≥10 leukocytes/mm3 of uncentrifuged urine) is not sufficient for diagnosis of bacteriuria [1-3]. This was illustrated in a study of urine samples from asymptomatic elderly women; 60 percent of samples with pyuria had no bacteriuria [2].

Voided clean catch specimens — Diagnostic criteria for clean catch specimens including number of specimens and minimum quantitative bacteria counts are outlined for women and men below. The definition of a positive urine culture in the setting of symptoms of cystitis is distinct and discussed in detail elsewhere. (See "Sampling and evaluation of voided urine in the diagnosis of urinary tract infection in adults", section on 'Definition of a positive culture'.)

Women — Asymptomatic bacteriuria in women is defined by the Infectious Diseases Society of America (IDSA) guidelines as two consecutive clean-catch voided urine specimens with isolation of the same organism in quantitative counts of ≥105 cfu/mL [4].

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Literature review current through: Nov 2017. | This topic last updated: Mar 28, 2017.
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