This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney disorders, Subject name: Pathology
[{'content': 'Most common infectious agent associated with chronic pyelonephritis is: \nSelect and explain. \nA. Proteus vulgaris, B. Klebsiella pneumonia, C. Staphylococcus, D. E.Coli', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Chronic pyelonephritis: Bacteriological examination of the urine reveals: E.Coli ( most common ) Proteus species Streptococcus faecalis Pseudomonas species Microscopic features: Tubular thyroidization (filled with colloid casts) Interstitial fibrosis and inflammation Obliterative endaeritis of vessels', 'role': 'assistant'}]