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

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pISSN 2288-0585 eISSN 2288-6850

Evaluation of Vitek and Disk Diffusion Susceptibility Testing of Enterobacteriaceae against Piperacillin-Tazobactam and Methicillin-Resistant Staphylococcus aureus against Trimethoprim-Sulfamethoxazole

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2005 December Volume 8, Issue 2, pages 160-164.


https://doi.org/10.5145/ACM.2005.08.2.160

Evaluation of Vitek and Disk Diffusion Susceptibility Testing of Enterobacteriaceae against Piperacillin-Tazobactam and Methicillin-Resistant Staphylococcus aureus against Trimethoprim-Sulfamethoxazole

Wonkeun Song*, Tae Jae Lee, Taek-Kyung Kim, Han-Sung Kim, Jae-Seok Kim, Min-Jeong Park, and Kyu Man Lee

Department of Laboratory Medicine, Hallym University College of Medicine, Seoul, Korea

Abstract

Background: The aim of this study was to evaluate the Vitek system and the disk diffusion method for susceptibility testing of Enterobacteriaceae against piperacillin-tazobactam (TZP) and methicillin-resistant Staphylococcus aureus(MRSA) against trimethoprim-sulfamethoxazole (SXT) using the broth microdilution method as the reference.

Methods: Using the Vitek system and the disk diffusion method, we tested 96 isolates of Enterobacteriaceae (48 Escherichia coli, 26 Klebsiella pneumoniae, 8 Serratia marcescens, 6 Enterobacter cloacae, 2 E. aerogenes, 2 K. oxytoca, 2 Citrobacter freundii, 2 Pantoea agglomerans) and 61 isolates of MRSA for susceptibity against TZP and SXT, respectively; the broth microdilution of National Committee for Clinical Laboratory Standards was used as the reference method.

Results: In the susceptibility testing of Enterobacteriaceae against TZP, Vitek system yielded 10 (10%) minor errors, and the disk diffusion method one (1%) very major and 13 (14%) minor errors. For the MRSA against SXT, the rate of categorical agreement between the reference method and the Vitek or the disk diffusion method was both 100%. The rates of agreement between the reference method and the Vitek system in term of MICs (within ±1 dilution) were 93% and 98% in the susceptibility testing of Enterobacteriaceae against TZP and MRSA against SXT, respectively.

Conclusion: Both Vitek system and disk diffusion method showed an acceptable level of accuracy for the susceptibility test of Enterobacteriaceae against TZP and MRSA against SXT.(Korean J Clin Microbiol 2005;8(2):160-164)

Keywords

Enterobacteriaceae, Methicillin-resistant Staphylococcus aureus, Piperacillintazobactam, Trimethoprim-sulfamethoxazole, Vitek, Disk diffusion