Escherichia coli O157:H7 What is E. coli O157:H7? Escherichia
coli (or simply E. coli) is one of the many groups of bacteria
that live in the intestines of healthy humans and most warm-
blooded animals. E. coli bacteria help maintain the balance of
normal intestinal flora (bacteria) against harmful bacteria and
synthesize or produce some vitamins. However, there are hundreds
of types or strains of E. coli bacteria. Different strains of E.
coli have different distinguishing characteristics. A particular
strain of E. coli known as E. coli O157:H7 causes a severe
intestinal infection in humans. It is the most common strain to
cause illness in people. It can be differentiated from other E.
coli by the production of a potent toxin that damages the lining
of the intestinal wall, causing bloody diarrhea. It is also
known as enterohemorrhagic E. coli. The CDC reports about 70,000
cases of this type of E. coli infection occur in the United
States each year. How is the E. coli infection spread? In 1982,
E. coli O157:H7