Escherichia coli O157

Escherichia coli O157 hit the headlines again recently, with several children who had visited petting farms in the south of England and several in Canada succumbing to infection.

Escherichia coli O157 infection causes severe symptoms, including abdominal pain and intestinal bleeding and diarrhea. In a few cases (2 to 7%) it can also cause kidney problems, that can in rare cases be chronically debilitating and sometimes lethal.

This strain of E. coli is usually found in cattle waste, and is sometimes transferred via food or water (specifically beef products and milk) to people, who then spread it to each other via the fecal-oral route. Good handwashing hygiene is key to prevention.

E. coli causes these health problems because it produces a poisonous chemical known as Shiga toxin.

Shiga toxins are a family of related toxins with two major groups, Stx1 and Stx2. They are named after Kiyoshi Shiga who first described the bacterial origin of dysentery caused by Shigella dysenteriae. The most common sources for Shiga toxin are the bacteria S. dysenteriae and the Shigatoxigenic group of Escherichia coli (STEC), of which O157:H7 is the most well known to the public, and several other enterohemorrhagic E. coli.

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