Evaluation of modified carbapenem inactivation method for suspected carbapenemase among Enterobacteriaceae clinical isolates

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// <![CDATA[ $('.header-date').hide();$('#titleAuthors').hide();$('#abstractHeader').hide(); // ]]> Beiwei Yu1, 2, *, Dong Dong2, 3, *, Mingxia Wang1, 2, Yan Guo2, 3, Dandan Yin4 and Fupin Hu2, 3 1Department of Laboratory Medicine, Jinhua People’s Hospital, Zhejiang Province, China 2Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China 3NHC Key Laboratory of Clinical Pharmacology of Antibiotics, Fudan University, Shangai, China 4The Clinical Microbiology Laboratory, Department of Nosocomial Infection Control, Children’s Hospital of Fudan University, Shanghai, China *These authors contributed equally to this work Correspondence to: Fupin Hu, email: hufupin@163.com Keywords: modified carbapenem inactivation method; carbapenemases; enterobacteriaceae; blaKPC-2; blaNDM-1 Received: August 09, 2017 Accepted: February 27, 2018 Published: June 26, 2018 ABSTRACT Modified carbapenem inactivation method (mCIM) testing was currently recommended by Clinical and Laboratory Standards Institute (CLSI) for detection of carbapenemase among Enterobacteriaceae clinical isolates. In this study, a panel of 145 clinical strains were collected for evaluating the mCIM for detection of carbapenemase. Antimicrobial susceptibility testing were performed by microbroth dilution and the results were interpreted according to CLSI guidelines. All strains were resistant to ertapenem with high MIC50 and MIC90 (64 mg/L –>128 mg/L). For blaNDM-1-positive or blaOXA-232-positive strains, the zone of inhibition of meropenem were all 6 mm despite the incubation time of 6 h, 18 h or 24 h. For 6 h, the zone of meropenem inhibition for most of carbapenemase-positive isolates were meet the positive criteria 6–15 mm. However, for carbapenemase-negative isolates, the zone of meropenem inhibition were 16–18 mm after 6 h incubation which should be considered indeterminate for standard incubating time such as 18 h or 24 h. After incubating for 18 h or 24 h, the zone of meropenem inhibition were 22–25 mm for carbapenemase-negative isolates and meet the negative criteria. Our study indicate mCIM is a simple and effective method to identify the carbapenemases producers among Enterobacteriaceae clinical isolates.

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