Drug-resistant superbugs pose a huge threat to human health. Currently, colistin is regarded as the last-line antimicrobial against extensively drug resistant (XDR) bacterial infections caused by pathogens, such as Salmonella, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Shigella and Acinetobacter baumannii. Unfortunately, the efficacy of colistin has been seriously compromised in the regular treatment of lethal bacterial infections, due to the emergence of mobilized colistin resistance gene-1 (mcr-1) first identified in 2015.