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: Pathology
[{'content': 'The most common infectious agent associated with chronic pyelonephritis is: \nSelect and explain. \nA. Proteus vulgaris, B. Klebsiella pneumonia, C. Staphylococcus aureus, D. Escherichia coli', 'role': 'user'}, {'content': 'Answer: D \nExplanation: . Escherichia coli', 'role': 'assistant'}]