ABSTRACT
Objective To evaluate the reliability of the inhibitor enhanced carbapenem inactivation method (ieCIM) in the detection and preliminary classification of carbapenemase in gram-negative rods.Methods The carbapenem inactivation method (CIM) was modified by adding tazobactam or ethylene diamine tetraacetic acid disodium salt as carbapenemase inhibitors into the reaction system.A total of 198 isolates of Enterobacteriaceae and 35 strains of nonfermenters were collected,and their preliminary classification of carbapenemase was performed by the ieCIM.Meanwhile,their carbapenemase genes were detected by polymerase chain reaction (PCR),and the results were compared with that of the ieCIM.Results Among 198 strains of Enterobacteriaceae,101 were positive for carbapenemase genes,while 99 were detected by the CIM.Among the other 97 strains with negative carbapenemase gene,the results of the ieCIM were also negative.Among 35 strains of nonfermenters,25 were positive for carbapenemase genes,while 24 were detected by the CIM.Among the other 10 strains with negative carbapenemase gene,the results of the CIM were also negative.Using the ieCIM,97.7％ (85/87) of strains producing class A carbapenemase and 88.0％ (22/25) of strains producing class B carbapenemase were detected.Twelve strains producing class D carbapenemase and 2 strains producing both class A and class B carbapenemase were detected by the ieCIM.The total detection sensitivity and specificity of the ieCIM were 96％ and 100％,respectively.Conclusion The ieCIM has the consistent results with the detection method of carbapenemase genes,which may be used to detect and classify carbapenemase in clinical microbiology laboratories.