Background and study aim: Polymyxins are considered the last remedy for multidrug-resistant Enterobacteriaceae. However, due to their overuse, Polymyxin resistance rose and posed the urge to find new methods to aid their rapid diagnosis. So, this study aimed to assess the diagnostic efficacy of the rapid polymyxin NP test for diagnosis of colistin and polymyxin-resistant Enterobacteriaceae and detect the frequency of mcr-1 and mcr-2 genes among the MDR-Enterobacteriaceae isolates‎‎.
Patients and Methods: This study included 42 isolates of MDR-Enterobacteriaceae that were subjected to broth microdilution method to detect the MICs for polymyxin B and colistin, rapid polymyxin NP test using Polymyxin B, and conventional PCR for the identification of Polymyxins resistant genes; mcr-1 and mcr-2‎‎‎‎‎‎‎.
Results: Eighteen out of 42 isolates were resistant to colistin (42.9%), while 15/42 were resistant to polymyxin (35.7%). For both colistin and polymyxin MIC, the polymyxin NP test exhibited an overall sensitivity, specificity, PPV, and NPV of (77.8%, 91.7%, 87.5%, 84.6%) and (93.3%, 92.6%, 87.5%, 96.2%) respectively. Seventeen isolates were positive for mcr-1 gene (40.5%) and five isolates were positive for mcr-2 gene (11.9%).
Conclusion: The rapid polymyxin NP test is an easy and quick that can reliably detect both polymyxin-resistant and susceptible Enterobacteriaceae isolates. This test can be implemented as a screening tool in the outbreak management and active surveillance for presence of Polymyxins resistance. Therefore, combined with PCR, it can play a substantial role to contain antimicrobial resistance and prevent transfer of resistance genes among patients‎‎‎‎‎‎‎.