Multiplex Colistin Resistance

Colistin (polymyxin E) represents one of the last-resort antibiotics for treatment of serious infections caused by extensively drug-resistant gram-negative bacteria including carbapenem-resistant Enterobacteriaceae and Pseudomonas aeruginosa. Emergence of colistin resistance through plasmid-mediated MCR (mobilized colistin resistance) genes represents an alarming development in global antimicrobial resistance, as colistin-resistant organisms have very limited treatment alternatives. MCR genes modify bacterial lipopolysaccharide (LPS) structure, reducing colistin binding and preventing antibiotic action. Multiple MCR gene variants (MCR-1 through MCR-9 and beyond) have been identified spreading globally through horizontal gene transfer on mobile genetic elements.