Final answer:
Hemorrhagic colitis is a severe form of gastrointestinal disease caused by Shiga toxin-producing Escherichia coli strains, such as EHEC O157:H7, leading to bloody diarrhea and potentially to hemolytic uremic syndrome.
Step-by-step explanation:
Hemorrhagic colitis is a gastrointestinal disease caused by certain strains of Escherichia coli (E. coli), often characterized by bloody diarrhea and severe abdominal cramps. The most notorious of these are enterohemorrhagic E. coli (EHEC) strains, such as O157:H7, which produce a fatal toxin known as Shiga toxin. Shiga toxin, which originated from Shigella dysenteriae, is capable of targeting the endothelial cells of the intestines and kidneys, leading to hemorrhaging and sometimes a life-threatening condition known as hemolytic uremic syndrome (HUS).
Upon entering target cells in the intestinal tract, Shiga toxin binds to the ribosomes, halting protein synthesis and causing cellular death. This process results in hemorrhagic colitis, marked by inflammation and bloody diarrhea, and in severe cases, may progress to HUS—where clumps of destroyed red blood cells obstruct the kidney's filtering system, possibly leading to kidney failure. Diagnosis of EHEC infection typically involves stool sample cultures and the use of MacConkey with sorbitol agar to differentiate EHEC from less virulent strains of E. coli. The Shiga toxin genes in EHEC are known to have been transferred from Shigella dysenteriae through horizontal gene transfer mediated by bacteriophage transduction, contributing significantly to the pathogenicity of these strains.