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E. coli O157:H7 Screening

E. coli O157:H7 is a gram-negative enteric pathogen which causes diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome throughout temperate regions of the world, including the US, Canada, northern Europe, Japan, South Africa, and South America.

E. coli O157:H7 is the second most common stool culture isolate in the Northeast and Northwest United States. It ranks fourth in the Midwest after Camypylobacter, Salmonella, and Shigella. Consumption of E. coli contaminated food, especially undercooked ground meat, is the primary cause of this disease. The organism has also been transmitted in water, unpasteurized milk, and other foods including turkey, mayonnaise, and cantaloupe. In addition, person-to-person transmission is a well-documented occurrence in households and day-care centers.

The hemolytic uremic syndrome (HUS) develops in approximately 10% of patients with E. coli O157:H7 infections. HUS is recognized by a triad of symptoms that includes reduced platelet count, fragmented erythrocytes, and renal failure. HUS is thought to be a toxemia, in which circulating bacterial lipopolysaccharide and Shiga-like toxins exert their combined influence on endothelial cells of specific organs, particularly the kidney.

E. coli O157:H7 requires selective culture media for isolation. Previously, most microbiology laboratory limited E. coli O157:H7 testing to visibly bloody stools or by request. Due to its increasing prevalence, all stools received for routine stool cultures should now be tested for this organism.

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