E. coli Bacteria Basics
E. coli O157:H7 is a strain of Escherichia coli that produces a powerful toxin and causes severe illness. is one of hundreds of strains of the bacterium Escherichia coli. E. coli O157:H7 was first recognized as a cause of illness in 1982 during an outbreak of severe bloody diarrhea; the outbreak was traced to contaminated hamburgers. Most infections have come from eating undercooked ground beef, but recent outbreaks have involved pre-washed lettuce, alfalfa sprouts, and raw milk. The combination of letters and numbers in the name of the bacterium refers to the specific markers found on its surface and distinguishes it from other types of E. coli.
E. coli bacteria live in the intestines of cattle. They infect the meat during the slaughter process. Produce can become infected if irrigated with infected water or if contaminated by cross-contamination, i.e., by coming in contact with raw meat.
When a person becomes infected with E. coli 0157:H7, the bacterial toxins irritate the intestines and often cause bloody diarrhea. Although many victims of E. coli recover within 5 to 10 days, some victims develop a complication called hemolytic uremic syndrome, in which the red blood cells are destroyed and the kidneys fail. According to the Centers for Disease Control (CDC), about 2%-7% of infections lead to this complication. In the United States, hemolytic uremic syndrome is the principal cause of acute kidney failure in children, and most cases of hemolytic uremic syndrome are caused by E. coli O157:H7.
E. coli O157:H7 is diagnosed by testing the stool for the bacteria. Anyone suspecting E. coli should request that the stool specimen be tested on sorbitol-MacConkey (SMAC) agar for this organism. All persons who suddenly have diarrhea with blood should get their stool tested for E. coli O157:H7.