E. coli: Escherichia coli 0157:H7, E. coli 0157:H7 (cont.)
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E. coli 0157:H7 Causes
As mentioned above, only a small number (10–100) of organisms are capable of causing disease in humans. Therefore, healthy people can become infected even if the contaminated food contains only a low number of E. coli 0157:H7. Almost all other EES E. coli strains require a much higher number (thousands to millions) of ingested organisms to cause disease. Researchers have suggested several reasons why E. coli o157:H7 is so aggressive. The bacteria can produce two types of toxins, termed Shiga (Stx 1 and Stx 2, also termed Vero toxins) toxins. These toxins are almost identical to the toxin produced by Shigella spp. and are capable of killing human intestinal cells by disrupting their protein synthesis. When the cells die, intestinal function is disrupted, and intestinal bleeding can occur. The toxins and the damage that occurs to the intestines can lead to kidney damage, anemia, platelet aggregation, and death.
In addition, researchers suggest that the pili (fimbriae) of these organisms provide an adhesive receptor that is specific for human intestinal cells. Although E. coli 0157:H7 has been isolated from many animal species (for example, cattle, goats, and sheep), it usually causes no problems in animals; however, animal feces and products like untreated milk can transmit the bacteria to humans. The CDC suggests that E. coli 0157:H7 strain is most likely responsible for the majority of "E. coli" outbreaks in the US.
Bhupinder Anand, MD
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