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Year : 2019  |  Volume : 37  |  Issue : 4  |  Page : 488--495

Performance of three commercial assays for colistin susceptibility in clinical isolates and Mcr-1 carrying reference strain

Chand Wattal, Neeraj Goel, Jaswinder Kaur Oberoi, Sanghamitra Datta, Reena Raveendran 
 Department of Clinical Microbiology and Immunology, Sir Ganga Ram Hospital, New Delhi, India

Correspondence Address:
Dr. Chand Wattal
Department of Clinical, Microbiology and Immunology, Sir Ganga Ram Hospital, Rajinder Nagar, New Delhi - 110 060
India

Objective: Commercially available antibiotic susceptibility tests (cAST) for colistin are reported to shows variable performance. The current controversy on the colistin susceptibility testing and scarce data from India has left the clinical laboratories in a dilemma on the appropriate and practical approach to tackle the colistin antimicrobial susceptibility testing (AST) issue. This study was aimed to evaluate the performance of commonly used cAST for colistin against broth microdilution (BMD) as the reference method in the clinical isolates. Materials and Methods: Colistin AST was performed on 225 nonduplicate isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii by BMD as the reference method and compared with Vitek-2, Micronaut-S and E-test. The accuracy of the various cASTs was analysed by assessing categorical and essential agreement (EA). Results: We observed an overall categorical agreement of 98.2%, 99.6% and 96.4% and EA of 92%, 92.4% and 72% for Vitek-2, Micronaut-S and E-test, respectively. Unacceptable rates of major error (10.5%) and very major error (21%) were observed for P. aeruginosa with Vitek-2 and E-test, respectively. All the categorical errors (CEs) (7.7%) with Vitek-2 were seen for minimum inhibitory concentrations ranging within two-fold dilution breakpoint of 2 mg/L. Conclusion: Micronaut-S was found to be an acceptable method for colistin AST. In contrast, E-test was unreliable in terms of EA. Vitek-2 was found to be reliable for colistin AST, although it was more prone to CE near the colistin breakpoints.

How to cite this article:
Wattal C, Goel N, Oberoi JK, Datta S, Raveendran R. Performance of three commercial assays for colistin susceptibility in clinical isolates and Mcr-1 carrying reference strain.Indian J Med Microbiol 2019;37:488-495

How to cite this URL:
Wattal C, Goel N, Oberoi JK, Datta S, Raveendran R. Performance of three commercial assays for colistin susceptibility in clinical isolates and Mcr-1 carrying reference strain. Indian J Med Microbiol [serial online] 2019 [cited 2020 Sep 29 ];37:488-495
Available from: http://www.ijmm.org/article.asp?issn=0255-0857;year=2019;volume=37;issue=4;spage=488;epage=495;aulast=Wattal;type=0