The ability to resist acid stress is required for with mamcolonize and establish a commensal relationship malian hosts. The ability to withstand acidic environments is a important factor in the virulence of E. coli O157: H7. Low infectious doses associated with enterohemorragic E. coli were attributed in part to its acid resistance (Arnold and Kaspar 1995; Benjamin and Datta 1995; Conner and Kotrola 1995; Cheville and others 1996). The virulence of E. coli O157: H7 partially depended on its ability to survive the low pH of the gastric stomach (Benjamin and Datta 1995; Tuttle and others 1999; Law 2000; Smith 2003). The AR in E. coli O157: H7 was induced during passage and growth of these bacteria in the intestinal tract of cat tle (Lin and others 1996) and acid-resistant E. coli O157: H7 were shed from cattle (Hovde and others 1999. )