Modified CIM-Test As a Useful Tool to Detect Carbapenemase Activity Among Extensively Drug- Resistant Klebsiella Pneumoniae, Escherichia Coli and Acinetobacter Baumannii
Abstract Background Timely detection of carbapenemases is essential for developing strategies to control the spread of infections by carbapenem-resistant isolates. The purpose of our study was to determine the epidemiology of carbapenemase genes among carbapenem resistant isolates of Acinetobacter baumannii, Klebsiella pneumoniae and Escherichia coli and to compare efficacy of modified Hodge Test (MHT), Carba NP and modified carbapenem inactivation method (mCIM) tests. Methods A total of 122 carbapenem-resistant clinical isolates including 77 K. pneumoniae, 39 A. baumannii, and six E. coli were collected from hospitalized patients. Three phenotypic methods, including MHT, Carba NP test and mCIM were used for investigation of carbapenemase production. In addition, polymerase chain reaction (PCR) was performed to detect carbapenemase encoding genes. Results The sensitivity and specificity of the MHT were 75.0% and 100% respectively. In addition, CarbaNP displayed 80.8% sensitivity and 100% specificity, whereas the sensitivity and specificity were 90.4% and 100% for the mCIM test, respectively. Among carbapenem-resistant isolates, 70, 84 and 87 isolates exhibited positive results according to MHT, CarbaNP test and mCIM, respectively. PCR indicated the presence of one or more carbapenemase genes in 119 of carbapenem-resistant isolates, with blaKPC and blaVIM being the most commonly encountered. Co-production of ‘KPC and VIM’, ‘KPC and IMP’ and ‘KPC and OXA-48’ was detected in nine, seven and three isolates, respectively. Conclusion Our results confirm that the mCIM test is a useful tool for the reliable detection of carbapenemases-activity in enterobacterial isolates, especially in clinical microbiological laboratories with limited resources.