The most common infectious agent associated with chronic pyelonephritis is: (A) Proteus vulgaris, (B) Klebsiella pneumonia, (C) Staphylococcus aureus, (D) Escherichia coli
Answer is D. 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