9NCCLS.M100-S14 M2-A8 Performance standards for an-timicrobial susceptibility testing,fourteenth informational supplement[S].Wayne,Pennsylvania:NCCLS,2004.
10Tadesse DA,Zhao S,Tong E,et al.Antimicrobial drug resistance in Escherichia coli from humans and food animals,United States,1950-2002[J].Emerging Infectious Diseases,2012,18(5):741-749.