Evaluation of Modified Rapid Carbapenem Inactivation Method (mrCIM) Combined with Rapid EDTA-Modified Carbapenem Inactivation Method (reCIM) to Detect Carbapenemase and Distinguish Metallo-Carbapenemase in Enterobacteriaceae Within Four Hours

Qiang Wei, Jide Sun, Zhu Wang, Li Yan, Chuanming Zhang, Xiuyu Xu Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of ChinaCorrespondence: Xiuyu XuDepartment of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, No. 1 Youyi Road, Yuzhong District, Chongqing 400016, People’s Republic of ChinaTel/ Fax +86-23-89012513Email xuxiuyu85@126.comPurpose: To develop a rapid EDTA-modified carbapenem inactivation method (reCIM) combined with modified rapid carbapenem inactivation method (mrCIM) to detect carbapenemase and distinguish metallo-β-lactamases from carbapenemases in Enterobacteriaceae in 4 hrs.Materials and Methods: The sensitivities and specificities of mrCIM and reCIM were retrospectively evaluated in 247 carbapenem-resistant Enterobacteriaceae of which 107 were carbapenemase producers confirmed by PCR and sequencing. In addition, mrCIM and reCIM were prospectively evaluated with 47 carbapenem-resistant enterobacterial isolates.Results: The sensitivity and specificity of mrCIM were 96.3% and 97.1% at 2.5 hrs post incubation, and the specificity increased to 98.6% at 3 hrs. The combined mrCIM and reCIM showed a sensitivity of 95.4% and a specificity of 100% at 2.5 hrs post incubation in identifying metallo-β-lactamases, and the sensitivity increased to 97.0% at 3 hrs. These performance characteristics are comparable to mCIM and eCIM; however, compared with mCIM and reCIM tests which need at least 24 hrs to detect results, the mrCIM and reCIM required less than 4 hrs of total work time.Conclusion: The combined mrCIM and reCIM can be used to accurately and quickly detect carbapenemase and metallo-β-lactamases in Enterobacteriaceae in 4 hrs and are suitable for routine use in most clinical microbiology laboratories.Keywords: modified rapid carbapenem inactivation method, rapid EDTA-modified carbapenem inactivation method, metallo-carbapenemase, Enterobacteriaceae, detection