4NCCLS.M100-S14 M2-A8 Performance standards for an-timicrobial susceptibility testing,fourteenth informational supplement[S].Wayne,Pennsylvania:NCCLS,2004.
5Tadesse 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.
6Hamett N M,Gles C L.Enterotoxin plasminds in bovine and porcine Enterotoxigenic Escheerichia coli of O group 9,20,64andl01[J].Can J Comp Med,1985,49(1):79-97.
7Maini J G.F.Bex.Prevalence of four enterotoxin(StaP,StaH,STb and LT)and four adhesion subunit(K99,K88,987P,and F41)genes among Escherichiacoli isolates from cattle[J].Am JVet Res,1990,51(1):187-190.