HEMATOGENOUS PYELONEPHRITIS IN RATS. IV. RELATIONSHIP OF BACTERIAL SPECIES TO THE PATHOGENESIS AND SEQUELAE OF CHRONIC PYELONEPHRITIS*†

Abstract

Chronic pyelonephritis was produced in more than 200 rats by combining repeated intracardiac inoculation of either Escherichia coli, Proteus morganii or Streptococcus zymogenes with renal massage. The animals were observed for as long as 1 year after initial infection. Since surgical intervention was not necessary to establish pyelonephritis, the resulting pathological lesions of the kidney were purely the product of chronic infection. Although a slight elevation of blood pressure above normal was noted in the rats infected with Proteus, significant hypertension did not develop. All groups demonstrated impaired renal function, as measured either by urea retention or by decrease in osmolal concentration of the urine after dehydratioa Although the overall pathologic changes produced by all 3 organisms were basically similar and showed a striking resemblance to chronic pyelonephritis in man, certain features characteristic of each bacterial species were noted. Thus infection with E. coli was self-limited, but the inflammatory process that persisted in these sterile kidneys was at least as severe as that in rats with heavily persistent enterococcal infections of the kidney. P. morganii produced marked renal destruction, stone formation and hydronephrosis. Infection with S. zymogenes was still present in every rat examined at the end of one year, but observable lesions often predominated in the renal medulla. The results demonstrate the importance of the bacterial species in determining the type and extent of renal injury in chronic pyelonephritis. Moreover, the absence of hypertensive vascular disease suggests several alternative hypotheses to the supposed etiologic relationship of hypertension to chronic pyelonephritis.