Clinical Significance of Low Colony-Count Urine Cultures Among Hospitalized Inpatients

Most hospital microbiology laboratories currently report uropathogen growth >104 colony-forming units per milliliter (CFU/mL) from all voided or catheter urine cultures.1 This threshold for reporting gained acceptance based on evidence suggesting that it confers improved sensitivity to detect acu...

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Bibliographic Details
Published in:Infection control and hospital epidemiology 2018-04, Vol.39 (4), p.488-489
Main Authors: Smith, Marc-André, Lamb, Michael J, Baillie, Laura, Simor, Andrew, Leis, Jerome A
Format: Article
Language:English
Subjects:
Antimicrobial agents
Asymptomatic
Clinical significance
E coli
Hospitalization
Laboratories
Medical instruments
Microbiology
Nursing
Patients
Urinary tract diseases
Urinary tract infections
Urine
Urogenital system
Yeasts
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Summary:Most hospital microbiology laboratories currently report uropathogen growth >104 colony-forming units per milliliter (CFU/mL) from all voided or catheter urine cultures.1 This threshold for reporting gained acceptance based on evidence suggesting that it confers improved sensitivity to detect acute cystitis in young female outpatients.2,3 The optimal threshold for reporting urine culture growth in hospitalized patients is not known. Before the threshold was lowered to improve sensitivity, >105 CFU/mL was suggested as early as the 1950s, based on evidence that it detected >95% of pyelonephritis cases.4 Sixty years later, there is increased appreciation for the potential harms of overdetection of asymptomatic bacteriuria (ASB) among hospitalized patients in driving unnecessary antimicrobial therapy and the emergence of antimicrobial resistance.5,6 We hypothesized that not routinely reporting urine cultures with colony counts 104–105 CFU/mL among hospitalized patients, unless specially requested by a clinician, would result in a significant decrease in antimicrobial use for ASB with minimal risk of underdetecting urinary tract infection (UTI). Following urine culture reporting, reflexive therapy for ASB was initiated in 49.6% of high colony-count specimens versus 35.6% of low colony-count specimens (P=.01).TABLE 1 Characteristics of Hospitalized Patients With Positive Urine Cultures With Low and High Colony Counts Characteristic Low Colony Count (n=348), No. (%)a High Colony Count (n=186), No. (%)b P Value Demographics Median age, y (range) 69 (19–96) 74 (22–96)
ISSN:0899-823X
1559-6834
DOI:10.1017/ice.2017.324