<prompt> Most common infectious agent associated with chronic pyelonephritis is:Proteus vulgarisKlebsiella pneumoniaStaphylococcusE.Coli  <response>: 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 