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First recognized as a human pathogen in 1982,E. coli O157: H7 causes an estimated 20,000 cases of diarrhea in the U.S. each year, of which 250 prove fatal. It is a leading cause of HUS, the most common cause of acute renal failure in children. Although most strains of E. coli are harmless, E. coli O157: H7 has integrated the gene that produces Shiga toxin, possibly by means of a virus which transferred the gene from Shigella to E. coli. Endothelial cells in the intestine, kidney and brain are the major targets of the toxin. Most outbreaks of O157:H7 have been associated with ground beef, but apple cider, lettuce, alfalfa sprouts, mayonnaise, cantaloupe and contaminated water have also been implicated. Although E. coli O157: H7 is the major cause of large Shiga toxin related outbreaks in the U.S., non-O157: H7 outbreaks have been documented. The number of sporadic cases due to other serotypes is unknown, but serotypes O111 and O104 have been associated with disease. HUS and colitis due to many other serotypes have been reported in other parts of the world since 1984. At least two reports of human disease caused by Shiga toxin producing Citrobacter freundii and Enterbacter cloacae have been reported. Currently there are no clear guidelines for who should be tested for Shiga toxin producing E. coli infection. Patients with either bloody or non-bloody diarrhea of any age may develop associated HUS. Screening tests for Shiga toxin producing bacteria other than O157: H7 are in development, but not yet available. |
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