One of hundreds of strains of the bacterium Escherichia coli. A form of bacteria that commonly lives in the intestines of healthy humans and animals; however, this strain produces a powerful toxin and can cause severe illness. The germ is present in uncooked beef, unpasteurized milk and juice, and on raw sprouts and lettuce. The strain was first recognized as a cause of illness in 1982 during an outbreak of severe bloody diarrhea; the outbreak was traced to contaminated hamburgers.