Prevalence of mcr-1 in commensal Escherichia coli from French livestock, 2007 to 2014.

Colistin resistance was investigated in 1,696 isolates collected from 2007 to 2014 within the frame of the French livestock antimicrobial resistance surveillance programme. The mcr-1 gene was detected in all commensal Escherichia coli isolates with a minimum inhibitory concentration to colistin above the 2 mg/L cut-off value (n=23). In poultry, mcr-1 prevalence was 5.9% in turkeys and 1.8% in broilers in 2014. In pigs, investigated in 2013, this prevalence did not exceed 0.5%. These findings support that mcr-1 has spread in French livestock.