E. coli is a Gram-negative bacterium found in the intestines of most
animals including humans. Although most strains of E. coli are innocuous,
some strains such as the Shiga toxin producing strain O157:H7
(STEC) and non O157:H7 Shiga toxin producing strains can cause illness
if ingested (Jaeger, 1999). E. coli O157:H7 is infectious at concentrations
as low as 10 organisms (Schmid-Hempel & Frank, 2007). Complications
arising from STEC strains of E. coli infections include cramps, vomiting,
bloody diarrhea, and blood in the urine, with severe infections leading
to kidney failure (Belongia et al., 1991). Contamination with STEC strains
of E. coli is often found in undercooked meat especially beef, unpasteurized
dairy products and raw fruits and vegetables.