Comparison of two phenotypic methods for the detection of carbapenemase production in Enterobacteriaceae

Carbapenemase production in Enterobacteriaceae constitutes the capacity of these bacteria to synthesize enzymes known as carbapenemases, which degrade carbapenem antibiotics, thus rendering them ineffective. This mechanism plays a pivotal role in promoting antibiotic resistance, therefore posing a formidable threat to public health by restricting therapeutic options for bacterial infections. The objective of the present study was to detect and compare the types of carbapenemase produced by two phenotypic methods: the modified carbapenem inactivation method (mCIM) combined with the EDTA carbapenem inactivation method (eCIM) and a combined disc test for carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Klebsiella pneumoniae (CRKP) and carbapenem-resistant Escherichia coli (CREC). A total of 112 clinical isolates of CRE were obtained, of which 87 (77.6%) were metallo-beta lactamase (MBL) producers and 2 (1.8%) were serine carbapenemase producers. Among the tracheal isolates, predominantly K. pneumoniae produced MBL, whereas among the urine isolates, predominantly Escherichia coli were MBL producers. Since imipenem+EDTA (indigenous) is cost effective and easy to perform under laboratory conditions, it can be considered a reliable phenotypic method for the detection of carbapenemase production.