The most common infectious agent associated with chronic pyelonephritis is
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
Proteus vulgaris
Klebsiella pneumonia
Staphylococcus aureus
Escherichia coli
Urinary tract