Distinct increase in antimicrobial resistance genes among Escherichia coli during 50 years of antimicrobial use in livestock production in China

Antimicrobial use in livestock production is linked to the emergence and spread of antimicrobial resistance (AMR), but large-scale studies on AMR changes in livestock isolates remain scarce. Here we applied whole-genome sequence analysis to 982 animal-derived Escherichia coli samples collected in China from the 1970s to 2019, finding that the number of AMR genes (ARGs) per isolate doubled—including those conferring resistance to critically important agents for both veterinary (florfenicol and norfloxacin) and human medicine (colistin, cephalosporins and meropenem).