Definition of E. coli

E. coli: Short for Escherichia coli, the colon bacillus, a bacterium that normally resides in the human colon. E. coli has been studied intensively in genetics and molecular and cell biology because of its availability, its small genome size, its normal lack of pathogenicity (disease-causing ability), and its ease of growth in the laboratory.

Most strains of E coli are quite harmless. However, some strains of E. coli are capable of causing disease, sometimes disease of deadly proportions. For example, an outbreak of E. coli O157:H7 bacteria in the water supply hit Walkerton, Ontario in the year 2000; the E. coli affected about 2,000 people in and around Walkerton and were responsible for the deaths of some 18 people.

E. coli 0157:H7 is a major health problem. About 20,000 cases of hemorrhagic (bloody) colitis (inflammation of the bowel) due to E. coli 0157:H7 occur each year in the U.S. E coli O157:H7 produces toxins (poisons). The toxins produced by E. coli 0157:H7 can damage the lining of the intestine and are thought to participate in all of the diseases caused by E. coli 0157:H7.

The hemorrhagic diarrhea (bloody colitis) caused by E. coli 0157:H7 is severe with painful abdominal cramps, gross blood in the stool, and lasts for 6 to 8 days.

Children with E. coli 0157:H7 can develop a disease called the hemolytic-uremic syndrome (HUS), a major and sometimes fatal "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. HUS is the most common cause of acute kidney failure in infants and young children.

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.

Most commonly, E. coli 01257:H7 comes 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.