Both pathogenic and nonpathogenic E. coli exhibit a stress response to sublethal environmental stresses (Murano and Pierson 1993; Arnold and Kaspar 1995; Hill and others 1995; Kauppi and others 1996; Buncic and Avery 1998; Ryu Buchat 1998; nanon and Drake. 2001). These stress responses can result in resistance to a variety of environmental or processing parame- ters (Lin and others 1996; Abee and Wouters 1999; Law 2000) The nature and the intensity of the stress response may vary between pathogenic and nonpathogenic coli and, moreover. , stress response varies widely between strains of pathogenic E. coli (Benjamin and Datta 1995; McKellar and Knight 1999, Duffy and others 2000a; Leenanon and Drake 2001).