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

Abstract

he 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. Because these bacteria usually remain susceptible to polymyxins, an old class of antimicrobial drugs almost abandoned in the 1970s because of their potential toxicity, interest in polymyxins (colistin and polymyxin B) has been renewed worldwide. The increasing use of colistin explains why acquired colistin resistance may now be added to the multi resistant traits in Enterobacteriaceae. Acquired resistance to colistin in Enterobacteriaceae results mostly from modification of lipopolysaccharide. Addition of phospho-ethanolamine, 4-amino-l-arabinose cationic groups, or both to lipopolysaccharide decreases polymyxin binding to the bacterial outer membrane. Addition of these groups may be associated with chromosome encoded mechanisms (mutations in Pmr AB or PhoPQ two-component systems or alterations of the mgr B gene).