A research collaborative recently found that bacteria that carry the colistin resistance gene mcr-1 commonly exist in food and environmental samples collected from Hong Kong and the Chinese mainland. The mcr-1 gene is a new plasmid-encoded colistin resistance mechanism discovered by scientists in China in 2015. Colistin has been a last-resort antibiotic used to treat severe infections caused by carbapenem resistant Enterobacteriaceae (CRE) strains. The prevalence of mcr-1 in the ecosystem challenges the role of colistin as the last-resort antibiotic to treat infections caused by CRE.