After 24 hours, this inoculated MacConkey agar culture plate cultivated colonial growth of Gram-negative Escherichia coli bacteria.
Normally, E. coli serves a useful function in the body by suppressing the growth of harmful bacterial species, and by synthesizing appreciable amounts of vitamins. A minority of E. coli strains are capable of causing human illness by several different mechanisms. E. coli serotype O157:H7 is a rare variety of E. coli that produces large quantities of one or more related, potent toxins that cause severe damage to the lining of the intestine. These toxins (VT), shiga-like toxin are closely related, or identical to the toxin produced by Shigella dysenteriae.