The most common infectious agent associated with chronic pyelonephritis is ?

Ans. is 'd' i.e., Escherichia coli Pyelonephritis Pyelonephritis refers to bacterial infection of the kidney. The infection involves the renal tubules, interstitium, and renal pelvis. The dominant etiologic agents, accounting for more than 85% of cases of urinary tract infection, are the gram-negative bacilli that are normal inhabitants of intestinal tract. By far the most common is Escherichia coli, followed by proteus, klebsiella, and Enterobacter. In most patients with urinary tract infection, the infecting organisms are derived from the patient's own fecal flora. This is thus a form of endogenous infection. There are two routes by which bacteria can reach the kidneys :? From the lower urinary tract, i.e. Ascending infection Most common Hematogenous spread Less common