ABSTRACT
Enterohemorrhagic E. coli (EHEC) of serotype O157:H7 causes hemorrhagic colitis, which is characterized by microangiopathic haemolytic anaemia, thrombocytopenia, and central nervous system symptoms (Karmali, 1989) that may develop into life-threatening renal failure involving hemolytic-uremic-syndrome (HUS), particularly with children. E. coli isolates are serologically distinguished on the basis of three major surface antigens: somatic (O), agella (H), and capsule (K) antigen. Although more than 100 E. coli serotypes produce Shiga-like toxins (SLTs), O157:H7 is the predominant serotype implicated in foodborne diseases. E. coli O157:H7 strains are sorbitol negative, β-d-glucuronidase negative, exhibit poor or no growth at 44.5°C, possess an attaching and effacing gene (eae), possess a 66-MDa plasmid, and express an uncommon 5000 to 8000 mol. wt. outer membrane protein (OMP; Padhye and Doyle, 1991). The infectious dose is considered to be about 1 CFU/g of raw food (Centers for Disease Control and Prevention, 1995; Grifn et al., 1994; Zhao, Doyle, and Wang, 1994).
