Closing the Gap Between Phenotypic and Genotypic Detection of Carbapenem Resistant Enterobacteriaceae by New Modified Carbapenem Inactivation Method DC01-DC04
Dr. Satyajeet K Pawar,
Associate Professor, Department of Microbiology, Krishna Institute of Medical Sciences,
Malakapur, Karad-415539, Maharashtra, India.
Introduction: Carbapenems have become one of the last resort of antimicrobials. But in last few years, Carbapenem Resistant Enterobacteriaceae (CRE) have been reported worldwide. Various phenotypic tests have been proposed for detection of carbapenemase activity including the newer modified Carbapenem Inactivation Method (mCIM) as advised by Clinical Laboratory Standard Institute (CLSI) 2017 guidelines.
Aim: Detection of CRE from clinical specimens with new mCIM method and its comparative evaluation with phenotypic and genotypic methods.
Materials and Methods: Study was conducted between January 2017 and December 2017 at KIMS, Karad. Total 66 CRE, isolated from 1634 clinical specimens and identified by VITEK 2 (Biomerieux, France) were included in the study. Phenotype screening was done by mCIM (CLSI 2017) method and was compared with Modified Hodge test (MHT) and Combined Disc Test (CDT) methods. Klebsiella pneumoniae ATCC BAA-1705 and Klebsiella pneumoniae ATCC BAA-1706 were used as positive and negative controls respectively. Molecular confirmation of these isolates for carbapenemase producing genes blaNDM-1, blaOXA-48, blaKPC was done by multiplex Polymerase Chain Reaction (PCR) study.
Results: Klebsiella pneumoniae (n=35) outnumbered the other bacterial species among 66 CRE included in the study. mCIM was positive for 65 (98.48%) out of 66 isolates while MHT and CDT was positive for 50 (75.75%) and 59 (89.39%) of CRE isolates respectively. All the CRE isolates showed presence of at least one carbapenemase producing gene.
Conclusion:The mCIM method is simple, less subjective, cost effective, reproducible and most sensitive method and plays important role in detection and prevention of spread of CRE, thereby, reducing morbidity and mortality, especially where there is lack of automation and molecular diagnostic facility.