The prevalence of mcr-1 and resistance characteristics of Escherichia coli isolates from diseased and healthy pigs.

Colistin has been used as the last-line antibiotic for Escherichia coli infections. Herein, we collected 102 E. coli isolates from diseased pigs and 204 from healthy ones in Henan province of China. Then, we screened antimicrobial resistance and mcr-1 of bacteria. There was 25.5% (78/306) mcr-1-positive porcine E. coli, in which 46 isolates (45.1%, 46/102) were obtained from diseased pigs; the others (15.7%, 32/204) were collected from healthy pigs (45.1% versus 15.7%, P=0.000). Meanwhile, the former presented more serious resistance to colistin, ceftiofur, cefquinome, gentamicin, amikacin, doxycycline, florfenicol, enrofloxacin, and olaquindox than those from healthy pigs, which were similar to the relations between isolates with or without mcr-1, except for amikacin and doxycycline. Also, the resistance profiles of mcr-1-positive E. coli were more extensive than those of mcr-1-negative isolates.