Use of the Combined Modified Carbapenem Inactivation Method and EDTA-modified Carbapenem Inactivation Method for Detection of Carbapenemase-Producing Enterobacteriaceae Causing Ventilator-associated Respiratory Infections

There is an alarming rise in carbapenem-resistant Enterobacteriaceae (CRE) causing nosocomial infections such as ventilator-associated respiratory infections (VARIs). The use of rapid phenotypic methods for the detection and differentiation of carbapenemases elaborated by these CRE would be helpful in providing timely empirical therapeutic options for management of these infections and preventing spread of these CRE strains in hospital settings. Hence, this study aimed to detect CRE among pathogens isolated from the endotracheal secretions received from suspected cases of VARIs and differentiate carbapenemases elaborated by these CRE using combined phenotypic methods, such as the modified carbapenem inactivation method (mCIM) and EDTA modified CIM (eCIM). This observational study was conducted over a period of 1 year in the Department of Microbiology and the intensive care unit of a tertiary care center. Carbapenem resistance was found in 75% of Klebsiella pneumoniae isolates and 50% of Escherichia coli isolates, of which 58.4% were metallo-??-lactamases and 41.6% were serine carbapenemase producers. In conclusion, the combination of the mCIM and eCIM could be useful as an epidemiological tool and be considered essential in deciding the initial antibiotic therapy, help reduce morbidity and mortality associated with VARIs, and guide hospital infection control practices.