This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'A 20-year-old man presented with hemorrhagic colitis. The stool sample grew Escherichia coli in pure culture. The following serotype of E.coli is likely to be a causative agent - \nSelect and explain. \nA. O157:H7, B. O159:H7, C. O107:H7, D. O55:H7', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Enterohemorrhagic E.coli dysentery can lead to complications like hemorrhagic uremic syndrome and hemorrhagic\xa0colitis.\nSerotypes’ associated with EHEC are O157:H7 and O26:H1\nSimilar illness also produced by Shigella dysenteriae type1', 'role': 'assistant'}]