Escherichia coli,generally is considered as a part of non-pathogenic intestinal normal flora of both humans and animals.E.coli particularly E.coli O157:H7 considered a public health problem bacteria that induced food-borne diarrhea,bloody diarrhea and hemolytic uremic syndrome(HUS)which occurring with average in 4% of infection cases in young and children,so The objectives of the present study were:Isolating and identifying the E.coli O157:H7 from urine samples of humans and sheep,Confirming the diagnosis of the E.coli O157:H7 by conventional PCR assay and Studying the pathological changes in the internal organs of infected mice.The conclusions of this study was:E.coli O157:H7 that was isolated from urine samples of sheep carried the virulent factor genes which were similar to the strains that induced UTIs of the humans.The pathological changes that were induced by E.coliO157:H7 were progressed into severe supportive reaction during 24-72hrs post-infection and The body started tolimit the infection by granulomatous reaction during 5-10 days post-infection.