Enterohemorrhagic Escherichia coli O157:H7 present in radish sprouts

Using cultivation, immunofluorescence microscopy, and scanning electron microscopy, we demonstrated the presence of viable enterohemorrhagic Escherichia coli O157:H7 not only on the outer surfaces but also in the inner tissues and stomata of cotyledons of radish sprouts grown from seeds experimentally contaminated with the bacterium. HgCl2 treatment of the outer surface of the hypocotyl did not kill the contaminating bacteria, which emphasized the importance of either using seeds free from E. coli O157:H7 in the production of radish sprouts or heating the sprouts before they are eaten.