Experimental Pyelonephritis: Enhancement of Infection after Delivery of Escherichia coli into the Arterial Supply of the Kidney

Few bacterial species are able to infect intact kidneys of experimental animals after intravenous inoculation. Pyogenic renal infection can result from intravenous inoculation of strains of coagulase-positive Staphylococcus aureus [1, 2], enterococcus [3], Corynebacterium renale [4], and Pseudomonas aeruginosa [5]. However, Escherichia coli and Klebsiella-Enterobacter very rarely produce such infections unless there is some abnormality of the urinary tract [6, 7]. It is not known why some bacterial species multiply in the normal urinary tract and others do not. After intravenous injection of 108 or 109 E. coli, organisms rapidly disappear from the blood stream of experimental animals and only 1/10,000 or less of the challenging dose can be recovered from the kidneys within a few hours of inoculation [8]. These relatively small numbers of organisms are probably easily destroyed by the defense mechanisms in the kidneys. It is conceivable that if much larger numbers of the organism were delivered to the kidneys, they might overcome the local host defense mechanisms.