Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology

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pISSN 2288-0585 eISSN 2288-6850

Performance of Modified-EUCAST Rapid Direct Antimicrobial Susceptibility Testing on Clinical Urine Samples

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2020 September, Volume 23, Issue 3, pages185-194.

https://doi.org/10.5145/ACM.2020.23.3.2

Performance of Modified-EUCAST Rapid Direct Antimicrobial Susceptibility Testing on Clinical Urine Samples

Justin Mugiraneza1, Mijung Kwon2, Daewon Kim2, Sang-Guk Lee2, Hyukmin Lee2, Dongeun Yong2
1Department of Global Health Security, Yonsei University Graduate school of Public Health, Seoul, 2Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Korea

Abstract

Background: The rapid antimicrobial susceptibility testing (AST) performed on urine samples would guide the adequate choice of antibiotics for obtaining better treatment outcomes in patients. Our study aimed to evaluate the performance of the modified-EUCAST (European Committee on Antimicrobial Susceptibility Testing) rapid direct AST on urine samples.

Methods: From >2,000 urine samples, a total of 128 urine samples containing bacterial counts of ≥2 × 104 CFU/mL with a uniform bacterial shape were initially included based on flow cytometry (Sysmex UF-1000i, Japan) and Gram staining, respectively. A total of 103 samples showing the presence of Enterobacteriaceae were finally selected in this study. The urine samples were directly inoculated on Mueller-Hinton agar, which was used in the current EUCAST rapid direct AST on blood samples. The size of the growth inhibition zones around antimicrobial disks was measured using a digital scanner (BIOMIC vision analyzer, Giles scientific, USA) and further confirmed by visualization with naked eyes after incubation for 4, 6, and 8 hours. The AST interpretations were compared to those of the conventional VITEK 2 AST system (bioMérieux, France) and the discrepancies between both tests were confirmed with the E-test.

Results: The antibiotics, namely ampicillin, cefazolin, aztreonam, ceftazidime, cefotaxime, cefoxitin, cefepime, gentamicin, ciprofloxacin, and cotrimoxazole showed excellent correlations with modified-EUCAST rapid direct test and conventional ASTs with >0.75 weighted kappa values. The categorical agreement of the rapid direct AST was 1,442 (93.3%), with 76 (4.9%) minor error, 9 (0.6%) major error and 18 (1.2%) very major error, implicating the reliability of this method for clinical application.

Conclusion: Performing the modified-EUCAST rapid direct AST on urine samples can predict reliable AST results within 8 hours. The rapid direct AST can help the physicians to initiate adequate antimicrobial treatment for urinary tract infections.

 

Keywords

Bacteremia, Blood culture, Blood volume, Educational inteAnti-bacterial agents, Antimicrobial Susceptibility Testing, Rapid methodsvention, Quality improvement