Comparative Evaluation of Multiplex Pcr and Routine Laboratory Phenotypic Methods for Detection of Carbapenemases among Gram Negative Bacilli

Abstract

Background: Carbapenem resistant pathogens cause infections associated with significant morbidity and mortality. Objective: This study evaluates the use of Multiplex PCR for rapid detection of carbapenemase genes among carbapenem resistant Gram negative bacteria in comparison with the existing phenotypic methods like modified Hodge test (MHT), combined disc test (CDT) and automated methods. Material and Methods: A total of 100 Carbapenem resistant clinical isolates, [Escherichia coli (25), Klebsiella pneumoniae (35) P. aeruginosa (18) and Acinetobacter baumannii (22)] were screened for the presence of carbapenemases (blaNDM-1 , blaVIM, blaIMP and blaKPC genes) by phenotype methods such as the modified Hodge test (MHT) and combined disc test (CDT) and the molecular methods such as Multiplex PCR. Results: Seventy of the 100 isolates were MHT positive while, 65 isolates were positive by CDT. All the CDT positive isolates with EDTA and APB were Metallo betalactamase (MBL) and K. pneumoniae carbapenemase (KPC) producers respectively. blaNDM-1 was present as a lone gene in 44 isolates. In 14 isolates blaNDM-1 gene was present with blaKPC gene, and in one isolate blaNDM-1 gene was present with blaVIM, gene. Only one E. coli isolate had a lone blaKPC gene. We didn’t find blaIMP gene in any of the isolates. Neither of the genes could be detected in 35 isolates. Conclusion: Accurate detection of the genes related with carbapenemase production by Molecular methods like Multiplex PCR overcome the limitations of the phenotypic methods and Automated systems.

Keywords

• blandm-1
• blavim
• blaimp blakpc genes
• combined disc test
• modified hodge test
• multiplex pcr