Polymyxin Resistance in Gram-negative Pathogens

Purpose of Review The polymyxins are one of the last line antimicrobial classes to retain activity against multidrugresistant Gram-negative bacilli. However, with the increased use of polymyxins in recent years, reports of resistance have also been increasing. We aimed to describe the mechanisms and occurrence of polymyxin resistance in Gram-negative organisms and propose strategies to overcome resistance. Recent Findings The most common mechanism of acquired resistance to the polymyxins is via modification of the bacterial outer membrane lipopolysaccharide. Global epidemiological surveillance studies have reported the occurrence of polymyxin resistance to be most common in Enterobacteriaceae, specifically Enterobacter species and Acinetobacter baumannii. Prevalence of polymyxin-resistant Gram-negative organisms varies significantly by geographical location. Summary Emergence of polymyxin resistance is of great concern, given the limited number of agents available to treat infections caused by multidrug-resistant Gram-negative organisms. Strategies to mitigate the development of polymyxin resistance include dose optimization and using polymyxin agents in combination with other highly active antimicrobial agents.