Escherichia coli O157∶H7 is a foodbome pathogen that poses a major threat to public health.Epidemiologic investigations have identified dairy cows,especially calves,are the principal reservoir ofE.coli O157 ∶ H7.In this study,based on the results,E.coli O157∶H7 was the main cause ofE.coli disease outbreak in late October,2015,and more than 90％ of newb calves died of serious diarrhea.Through further experiments,the drug sensitivity and resistance of the strain,the expression of the virulence gene and virulence pathogenicity were studied.E.coli O157∶ H7 isolates were resistant to 12 antibiotics including penicillin,tetracycline and ampicillin,and were sensitive to eight antibiotics including cefoperazone,ceftazidime and amikacin.Resistance genes included tetB,strB,aadB,aphA,floR,TEM and virulence genes included stxl,eaeA and hlyA.Using specific pathogen free mice,the result showed that the isolate was pathogenic with a median lethal dose of 7.9× 107 CFU· mL-1.This study described the pathogenesis and clinical manifestations of E.coli O157 ∶H7 infection.These results guided the use of antibiotics in prevent and control of bacterial infections in the future.