Comparative Evaluation of Multiplex PCR and Routine Laboratory Phenotypic Methods for Detection of Carbapenemases among Gram Negative Bacilli
DC23-DC25
Correspondence
Dr. Rachana Solanki,
Senior Resident, Department of Microbiology, Nizam s Institute of Medical Sciences,Panjagutta, Hyderabad – 500082, Telangana, India.Phone : 0091-040- 66618773, Fax : 0091- 040 - 23310076, E-mail : lakshmi57vemu@gmail.com
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 ( bla NDM - 1 , bla VIM , bla IMP and bla KPC 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. bla NDM - 1 was present as a lone gene in 44 isolates. In 14 isolates bla NDM - 1 gene was present with bla KPC gene, and in one isolate bla NDM - 1 gene was present with bla VIM , gene. Only one E. coli isolate had a lone bla KPC gene. We didn’t find bla IMP 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.