Urine colony counts.
A Urine colony counts should always be done per isolate and not as a total colony count of all organisms. For example, if a clean-catch urine culture grew greater than 100,000 cfu/mL of E coli and 5,000 cfu/mL of a coagulase-negative staphylococci (CNS), you would want to report as in Example A, not as in Example B.
Example A) APPROPRIATE
>100,000 cfu/ml E coli
5,000 cfu/mL CNS (or insignificant growth)
Example B) NOT APPROPRIATE
>100,000 cfu/mL E coli and CNS
Example A appropriately confers the culture results, where Example B could lead a clinician to treat for both E coli and the coagulase-negative Staphylococcus, when only treatment of the E coli would be appropriate as the 5,000 cfu/mL of the CNS most likely represents contamination.
Table 1 below lists general guidelines for urine culture interpretation and work up for one or more potential pathogens from urine cultures. Often, we do not receive patient history with our urine specimens for culture. In this case, Table 2 gives general guidelines that might be used.
--Susan E. Sharp, PhD, D(ABMM)
Director of Microbiology, Kaiser Permanente Pathology
Regional Laboratory; Associate Professor, Oregon Health and Science University
1. Forbes BA, Sahm DF, Weissfeld AS, eds. Bailey and Scott's Diagnostic Microbiology. 10th ed. St. Louis, MO: Mosby; 1998.
2. Mandell GL, Bennett JE, Dolin R, eds. Principles and Practices of Infectious Diseases. 5th ed. New York, NY: Churchill Livingston; 2000.
Edited by Daniel M. Baer, MD
MLO's "Tips from the Clinical Experts" provides practical, up-to-date solutions to readers' technical and clinical issues from a panel of experts in various fields. Readers may send questions to Dan Baer by e-mail at firstname.lastname@example.org.
Table 1 Specimen type and/or Result patient history Work-up >[10.sup.4] cfu/mL of a CC/MS, IDC from patients Work up the one single PP or for each with pyelonephritis, or both PP with of 2 PP acute cystitis, or ID/AST asymptomatic bacteruria, OR SC >[10.sup.3] cfu/mL of a CC/MS, IDC from symptomatic Work up PP with single pp male patients, OR SC, OR ID/AST acute urethral syndrome >3 PP CC/MS, IDC, SC No work up 1 PP at >[10.sup.5] cfu/mL CC/MS, IDC Work up the one with 1 to 2 PP at PP at <[10.sup.4] cfu/mL >[10.sup.5] cfu/ml with ID/ AST 1 PP at >[10.sup.4] cfu/mL SC Work up the one with 1 to 2 PP at PP at <[10.sup.3] cfu/mL >[10.sup.4] cfu/ml with ID/ AST >[10.sup.2] cfu/mL of any SB Work up all PP PP with ID/AST Table 2 Specimen type and result Work-up CC/MS: [greater than or equal to] Work up the one or both PP [10.sup.4] cfu/mL of a single PP or for with ID/AST each of 2 PP SC: [greater than or equal to] Work up the one or both PP [10.sup.3] cfu/mL of a single PP or for with ID/AST each of 2 PP CC/MS, SC: [greater than or equal to]3 PP No work up CC/MS: 1 PP at [greater than or equal to] Work up the one PP at [10.sup.5] cfu/mL with 1 to 2 PP at [greater than or equal to] <[10.sup.4] cfu/mL [10.sup.5] cfu/mL with ID/AST SC: 1 PP at [greater than or equal to] Work up the one PP at [10.sup.4] cfu/ml with 1 to 2 PP at [greater than or equal to] <[10.sup.3] cfu/mL [10.sup.4] cfu/mL with ID/AST SB: [greater than or equal to][10.sup.2] Work up PP (up to three) with cfu/mL of up to 3 PP ID/AST Key to tables: CC/MS = clean catch and/or midstream IDC = indwelling catheter SC = straight catheter ID/AST = identification and antimicrobial susceptibility testing (if appropriate) PP = potential pathogen SB = suprapubic urine aspirates or other surgical obtained urine specimens