This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urinary tract, 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: In most urinary tract infections, the infecting organisms are derived from the patient's own fecal flora. The most common is E.coli, followed by Proteus, Klebsiella, and Enterobacter. Ref: Pathologic basis of disease Robbins, volume 2, Pg no:930", 'role': 'assistant'}]