Evaluation of Polymyxin NP Test as a Rapid Method for Detection of Colistin Resistance in Enterobacteriaceae

Abstract Background The carbapenemase-producing Enterobacteriaceae are among the most clinically significant multidrug-resistant bacteria. Its rise has led to an increase in the use of the polymixin B and colistin because of limited effective alternative antibiotic treatment. Aim of the Work Evaluation of the diagnostic efficacy of the rapid polymyxin NP test for the detection of colistin-resistant Enterobacteriaceae. Materials and Methods The study included a total of 42 Enterobacteriaceae isolates. All isolates were subjected to determination of the minimum inhibitory concentration (MIC) for colistin and polymyxin B using the broth microdilution method and detection of colistin-resistant isolates using the polymyxin NP test. Results Compared to the colistin MIC, the polymyxin NP test overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 64.7%, 92%, 84.6% and 79.3% respectively. On the other hand, a higher sensitivity (91.6%), specificity (93.3%), PPV (84.6%) and NPV (95.5%) were obtained when the results were compared to the polymyxin B MIC results. Conclusion The rapid polymyxin NP test is easy-to-perform, rapid, sensitive, specific test that can be used for the routine detection of polymyxin resistant Enterobacteriaceae particularly in poor resource laboratories.