Scientists are saying the deadly E.coli bacteria can be found not only on the surface of the vegetables but inside plant tissues as well. This means that, if contaminated with the pathogen, no amount of washing can remove them from foods such as spinach and lettuce.

The bacteria, according to the research, enters through the water absorbed by the plant root. Because the usual source of E.coli are organic fertilizers containing animal manure, this may have a significant impact on the growing organic food sector.

At least 114 victims in at least 21 states were brought down by E.coli after eating raw spinach from a California company that produces organic fresh vegetables.

Escherichia coli is one of the main species of bacteria that live in the lower intestines of mammals. The bacteria are necessary for the proper digestion of food and are part of the intestinal flora but only one strain (E. coli strain O157:H7) out of thousands causes illness in humans.