Evaluation of the Rapid Polymyxin NP test for detection of colistin susceptibility in Enterobacteriaceae isolated from Thai patients

Development and evaluations of the Rapid Polymyxin NP test for detection of colistin resistance in Enterobacteriaceae have been recently reported. In this study, we evaluated the performance of the test using a larger number of Enterobacteriaceae, and a larger proportion of isolates with a colistin MIC close to the breakpoint. Out of 339 isolates, the Rapid Polymyxin NP test detected colistin resistance in 13 isolates of Escherichia coli, 213 isolates of Klebsiella pneumoniae, 9 isolates of Enterobacter aerogenes, and 10 isolates of the other Enterobacteriaceae species. Sensitivity and specificity of the test for detecting colistin resistance were 100% and 95.9%, respectively. Positive predictive value and negative predictive value were 98.3% and 100%, respectively.