Selection of Unnecessary Urine Culture Specimens Using Sysmex UF-5000 Urine Flow Cytometer

두열 송1   철훈 정1   수민 이1   수민 이1   철훈 정*1   

1 Department of Laboratory Medicine, Pusan National University School of Medicine, Yangsan

Abstract

Background: Urine culture is one of the most frequently requested tests in microbiology. Automated urine analyzers yield much infection-related information. The Sysmex UF-5000 analyzer (Sysmex, Japan) is a new flow cytometry urine analyzer capable of quantifying urinary particles, including bacteria, WBCs, and yeast-like cells (YLCs) and can provide a Gram stainability flag. In this work, we evaluated how many unnecessary urine cultures could be screened out using the UF-5000.

Methods: We compared the culture results of 126 urine samples among 453 requested urine cultures (from sources other than the Urology and Nephrology departments) with urinalysis results. Urine cultures were considered positive if bacterial or YLC growth was ≥104 CFUs/mL.

Results: We used urinalysis cut-off values of 50/μL and 100/μL for bacteria and YLC, respectively. Forty eight of the 126 (38.1%, or 10.6% of 453 requested) cultures were below these cut-off values and did not contain any culture-positive samples.

Conclusion: Bacteria and YLC counts generated using the UF-5000 analyzer could be used to screen out negative cultures and reduce urine culture volume by ∼10% without sacrificing detection of positive cultures. (Ann Clin Microbiol 2018;21:75-79)

Keywords

Sysmex UF-5000 flow cytometer   Unnecessary urine cultures   Urinary tract infection   


Acknowledgements

This work was supported by the annual clinical research grant from Pusan National University Yangsan Hospital (2018).

Figures & Tables

Fig. 1. Classification of culture negative urine samples using the three urinalysis parameters. 1) LE (N), negative (‒) or trace (+/‒) leukocyte esterase by urine reagent strip analysis; 2) nitrite (N), negative (‒) nitrite by urine reagent strip analysis; and 3) Flag (N), no or unclassified flag by UF-5000 analysis. Abbreviations: LE, leukocyte esterase; N, negative


Figures & Tables

Table 1. Microorganisms and number isolated in urine cultures

MicroorganismNo.
Enterococcus faecalis7
Enterococcus faecium5
Granulicatella adiacens1
Staphylococcus epidermidis2
Gram-positive nonsporeforming bacilli2
Acinetobacter baumannii2
Citrobacter freundii1
Enterobacter cloacae1
Escherichia coli12
Klebsiella pneumoniae3
Proteus mirabilis2
Pseudomonas aeruginosa2
Candida albicans2
Candida glabrata3
Candida tropicalis1
Total46