Definition of E. coli O157:H7

E. coli O157:H7: A dangerous form of Escherichia coli, the colon bacillus, a bacterium that normally lives in the human colon.

E. coli 0157:H7 is a major health problem, causing hemorrhagic colitis, the hemolytic-uremic syndrome, and thrombotic thrombocytopenic purpura:

• Hemorrhagic colitis -- E coli O157:H7 causes about 20,000 cases of hemorrhagic colitis (bloody inflammation of the colon) a year in the US. The bacteria produce toxins that can damage the lining of the intestine. The colitis caused can be quite severe with painful abdominal cramps, diarrhea and grossly visible blood in the stool, lasting for 6 to 8 days.

• Hemolytic-uremic syndrome (HUS) -- Some children infected with E. coli 0157:H7 develop the hemolytic-uremic syndrome (HUS). Hemolytic" refers to the breakup of red blood cells. This leads to anemia and a shortage of platelets (thrombocytopenia) which causes abnormal bleeding. "Uremic" refers to the acute kidney failure. Central nervous system problems with seizures and coma can also occur. The hemolytic-uremic syndrome (HUS) is the most common cause of acute kidney failure in infants and young children.

• Thrombotic thrombocytopenic purpura (TTP) -- Persons who get E. coli 0157:H7, particularly the elderly, can develop a syndrome similar to HUS called thrombotic thrombocytopenic purpura (TTP) with anemia due to fragmentation of red blood cells, shortage of platelets (thrombocytopenia) with easy bruising, neurologic abnormalities, impaired kidney function, and fever.

Infection with E. coli 01257:H7 comes most often from eating raw or undercooked ground beef (hamburger) or from drinking raw milk or contaminated water. Less commonly, E coli O157:H7 can be transmitted from one person to another.