College of Veterinary Medicine;
Northeast Agricultural University;
Harbin 150030;
China;
Yichun Customs District P.R.China;
Yichun 153000;
Heilongjiang;
China;
Heilongjiang Key Laboratory for Animal Disease Control and Pharmaceutical Development;
Harbin 150030;
China;
E.coli; broth microdilution(BMD)method; epidemiological cut-off value(ECV); mcr-1; mcr-4; colistin;