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pISSN 2950-9114 eISSN 2950-9122
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Original Article

J Lab Med Qual Assur 2015; 37(4): 209-213

Published online December 31, 2015

https://doi.org/10.15263/jlmqa.2015.37.4.209

Copyright © Korean Association of External Quality Assessment Service.

Discordance in Colistin Susceptibility Test for Acinetobacter baumannii Showing Resistance: MicroScan versus Etest

Goeun Kang, Hyun Soo Kim, Han-Sung Kim, Wonkeun Song, and Jae-Seok Kim

Department of Laboratory Medicine, Hallym University Kangdong Sacred Heart Hospital, Hallym University College of Medicine, Seoul, Korea

Correspondence to:Jae-Seok Kim
Department of Laboratory Medicine, Hallym University Kangdong Sacred Heart Hospital, Hallym University College of Medicine, 150 Seongan-ro, Gangdong-gu, Seoul 05355, Korea
Tel: +82-2-2224-2327 Fax: +82-2-2224-2214 E-mail: jaeseok@hallym.or.kr

Received: September 2, 2015; Revised: October 21, 2015; Accepted: November 3, 2015

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background: Acinetobacter baumannii causes various hospital-acquired infections, its multidrug resistance is rapidly increasing worldwide. Although colistin is used in treatments against multidrug-resistant A. baumannii , resistance to colistin has also been reported recently. Few studies have reported colistin susceptibility testing using MicroScan. In this study, we compared colistin susceptibility tests for resistant A. baumannii by MicroScan (Siemens, USA) and Etest (BioMerieux, France).
Methods: We collected 115 A. baumannii clinical isolates, showing colistin resistance (minimum inhibitory concentration [MIC] ≥4 µg/mL) by MicroScan, from July 2014 to March 2015 at Kangdong Sacred Heart Hospital. Species identification and antimicrobial susceptibility tests were performed using the MicroScan Neg Combo Panel Type 72. Additionally, Etest was also performed for comparison.
Results: Of the 115 isolates, Etest revealed that 103 (89.6%) were colistin-susceptible (MIC ≤I µg/mL). Moreover, 52 isolates, showing a MIC of 4 µg/mL by MicroScan, were all susceptible to colistin. Only 12 (19.0%) of 63 isolates, showing a MIC of >4 µg/mL by MicroScan were resistant to colistin according to the Etest.
Conclusions: The MicroScan automated system, using the commercial broth microdilution method, exhibited some discrepancies with the Etest for colistin susceptibility in A. baumannii. Therefore, more practical and reliable susceptibility tests for colistin are required in clinical laboratories using MicroScan.

Keywords: Acinetobacter baumannii , Colistin, Microbial sensitivity tests, MicroScan, Etest

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