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Redefining urinary tract infections by bacterial colony counts.
Pediatrics. 2010 Feb; 125(2):335-41.Ped

Abstract

OBJECTIVES

To determine the best urinary bacterial concentration to diagnose urine infections.

METHODS

We studied a quantitative culture of paired urine samples from children that were promptly tested together after serial dilution. The initial diagnosis of urinary tract infection made from the result of the first urine culture and subsequently modified according to the second sample result, and then the ratio of their colony counts was considered. A total of 203 children (aged 2.0 weeks to 17.7 years) were screened for urine infection in a hospital setting.

RESULTS

The 36 children who had a urinary tract infection, defined as having the same uropathogen in both urine samples at concentrations within 25-fold of each other, had a mean colony count of 1.7 x 10(7) colony-forming units/mL. Among the 167 children who did not have a urinary tract infection, 12 (7.2%) would have had a false-positive diagnosis made on the first sample, which was revealed because the second sample result was different (n = 7) or had a > or =25-fold different colony count (n = 5). Raising the threshold from 10(5) to 10(6) colony-forming units/mL reduces the false-positive rate 4.8%. If 2 samples are cultured, the false-positive rates fall to 3.6% and 0.6%, respectively. All 9 children (5.4% of those without a urinary tract infection) who had a mixed culture with > or =10(5) colony-forming units/mL of a uropathogen (heavy mixed growth) in the first sample had a urine infection excluded by the second sample result.

CONCLUSION

The minimum urinary bacterial concentration that is used to diagnose a urine infection should be increased from > or =10(5) to > or =10(6) colony-forming units/mL, because that would reduce the false-positive rate from 7.2% to 4.8% if 1 sample was cultured and from 3.6% to 0.6% if 2 samples were cultured. Urine samples with heavy mixed growths should be considered contaminated.

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Publisher Full Text

Authors+Show Affiliations

Coulthard MG
BSc, MB BS, FRCP, Department of Paediatric Nephrology, Royal Victoria Infirmary, Newcastle NE1 4LP, United Kingdom. malcolm.coulthard@nuth.nhs.uk
Kalra M
No affiliation info available
Lambert HJ
No affiliation info available
Nelson A
No affiliation info available
Smith T
No affiliation info available
Perry JD
No affiliation info available

MeSH

ChildColony Count, MicrobialFalse Positive ReactionsHumansSensitivity and SpecificitySpecimen HandlingUrinary Tract Infections

Pub Type(s)

Journal Article

Language

eng

PubMed ID

20100747

Citation

Coulthard, Malcolm G., et al. "Redefining Urinary Tract Infections By Bacterial Colony Counts." Pediatrics, vol. 125, no. 2, 2010, pp. 335-41.
Coulthard MG, Kalra M, Lambert HJ, et al. Redefining urinary tract infections by bacterial colony counts. Pediatrics. 2010;125(2):335-41.
Coulthard, M. G., Kalra, M., Lambert, H. J., Nelson, A., Smith, T., & Perry, J. D. (2010). Redefining urinary tract infections by bacterial colony counts. Pediatrics, 125(2), 335-41. https://doi.org/10.1542/peds.2008-1455
Coulthard MG, et al. Redefining Urinary Tract Infections By Bacterial Colony Counts. Pediatrics. 2010;125(2):335-41. PubMed PMID: 20100747.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Redefining urinary tract infections by bacterial colony counts. AU - Coulthard,Malcolm G, AU - Kalra,Monika, AU - Lambert,Heather J, AU - Nelson,Andrew, AU - Smith,Terry, AU - Perry,John D, Y1 - 2010/01/25/ PY - 2010/1/27/entrez PY - 2010/1/27/pubmed PY - 2010/3/5/medline SP - 335 EP - 41 JF - Pediatrics JO - Pediatrics VL - 125 IS - 2 N2 - OBJECTIVES: To determine the best urinary bacterial concentration to diagnose urine infections. METHODS: We studied a quantitative culture of paired urine samples from children that were promptly tested together after serial dilution. The initial diagnosis of urinary tract infection made from the result of the first urine culture and subsequently modified according to the second sample result, and then the ratio of their colony counts was considered. A total of 203 children (aged 2.0 weeks to 17.7 years) were screened for urine infection in a hospital setting. RESULTS: The 36 children who had a urinary tract infection, defined as having the same uropathogen in both urine samples at concentrations within 25-fold of each other, had a mean colony count of 1.7 x 10(7) colony-forming units/mL. Among the 167 children who did not have a urinary tract infection, 12 (7.2%) would have had a false-positive diagnosis made on the first sample, which was revealed because the second sample result was different (n = 7) or had a > or =25-fold different colony count (n = 5). Raising the threshold from 10(5) to 10(6) colony-forming units/mL reduces the false-positive rate 4.8%. If 2 samples are cultured, the false-positive rates fall to 3.6% and 0.6%, respectively. All 9 children (5.4% of those without a urinary tract infection) who had a mixed culture with > or =10(5) colony-forming units/mL of a uropathogen (heavy mixed growth) in the first sample had a urine infection excluded by the second sample result. CONCLUSION: The minimum urinary bacterial concentration that is used to diagnose a urine infection should be increased from > or =10(5) to > or =10(6) colony-forming units/mL, because that would reduce the false-positive rate from 7.2% to 4.8% if 1 sample was cultured and from 3.6% to 0.6% if 2 samples were cultured. Urine samples with heavy mixed growths should be considered contaminated. SN - 1098-4275 UR - https://www.unboundmedicine.com/medline/citation/20100747/Redefining_urinary_tract_infections_by_bacterial_colony_counts_ L2 - http://pediatrics.aappublications.org/cgi/pmidlookup?view=long&pmid=20100747 DB - PRIME DP - Unbound Medicine ER -