Urine colony counts.

Q Could you give me the "pros and cons" of doing a total colony count on a urine culture vs. doing individual colony counts on pathogens in a urine culture. We are in the process of standardizing several labs in our system, and this is an issue for which we cannot find much information to reference.

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

Portland, OR

Resources

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 [email protected].

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: = 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: = 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: =3 PP No work up
CC/MS: 1 PP at = Work up the one PP at
 [10.sup.5] cfu/mL with 1 to 2 PP at =
 <[10.sup.4] cfu/mL [10.sup.5] cfu/mL with ID/AST
SC: 1 PP at = Work up the one PP at
 [10.sup.4] cfu/ml with 1 to 2 PP at =
 <[10.sup.3] cfu/mL [10.sup.4] cfu/mL with ID/AST
SB: =[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