The Discrepancy of the Minimum Inhibitory Concentration Results for Methicillin-Resistant Staphylococcus aureus by Various Measurement Methods
Yuka Kitano1, Shigeki Fujitani1, Haruaki Wakatake1, Machi Yanai1, Sari Umekawa1, Yosuke Homma2, Yasuhiko Taira1*
1Department of Emergency and Critical Care Medicine, St. Marianna University Hospital, Kawasaki City, Japan
2Department of Emergency Medicine, Tokyo Bay Urayasu Ichikawa Medical Center, Japan
- *Corresponding Author:
- Yasuhiko Taira, MD
2-16-1 Sugao Miyamae-ku
Kanagawa Prefecture, Japan-216-8511
Tel: +81-44-977-8111 ext 3931
E-mail: [email protected]
Received Date: September 21, 2015; Accepted Date: November 12, 2015; Published Date: November 19, 2015
Citation: Kitano Y, Fujitani S, Wakatake H, Yanai M, Umekawa S, et al. (2015) The Discrepancy of the Minimum Inhibitory Concentration Results for Methicillin-Resistant Staphylococcus aureus by Various Measurement Methods: A Comparison of Etest® and Microdilution Methods for Vancomycin, Teicoplanin, Linezolid, Daptomycin and Quinupristin-Dalfopristin. Emergency Med 5:286. doi:10.4172/2165-7548.1000286
Copyright: © 2014 Kitano Y, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
It has been postulated that there exists a discrepancy of methicillin-resistant Staphylococcus aureus
(MRSA) minimum inhibitory concentration
(MIC) results from various measurement methods. The association between higher MRSA MIC (MIC ≥ 2 μg/ml) and worse clinical outcome has been previously reported. Therefore, it is clinically essential to investigate whether such a discrepancy exists between the different MIC measurement methods.
From November 2009 to March 2011, 55 MRSA isolates were prospectively obtained at two emergency departments in Japan. The MIC of the isolates were measured by Etest® and five broth microdilution (BMD) methods, namely Eiken®, MicroScan® prompt method, MicroScan® turbidity method, Phoenix
® and Vitek2® system, respectively. The MIC results of vancomycin, teicoplanin, linezolid, daptomycin and quinupristin-dalfopristin (Q-D) were evaluated. Statistical analysis was performed using the Wilcoxon signed rank test and Bland-Altman’s analysis.
Results: There was a tendency of constant and significant discrepancy of MIC results of anti-MRSA antibiotics between Etest® and the BMD methods for MRSA isolates. The averages of the vancomycin MIC were 1.86 μg/ ml in Etest® and 0.74 μg/ml in the Phoenix® method (p<0.01), respectively. For teicoplanin, they were 1.86 μg/ml and 0.60 μg/ml (p<0.01), and for linezolid they were 2.55 μg/ml and 1.18 μg/ml (p<0.01) with respect to Etest® and the Phoenix® method, respectively. Among the BMD methods, however, the MicroScan® prompt method and the MicroScan® turbidity method had less discrepancy from Etest® for vancomycin MIC measurement.
Conclusion: The MIC measured by various BMD methods tended to show consistently lower results compared to those measured by Etest®. Among the BMD methods, however, the MicroScan® prompt method and the MicroScan® turbidity method had less discrepancy from Etest® for vancomycin MIC measurement.