URETHRAL OBSTRUCTION OF 6 HOURS OR LESS CAUSES BACTERIURIA, BACTEREMIA, AND PYELONEPHRITIS IN MICE CHALLENGED WITH NONUROPATHOGENIC ESCHERICHIA-COLI

Urethral obstruction may be caused by prostatic hypertrophy, urethral stricture, or encrustation of a urethral-catheter lumen. Bacteriuria o ften complicates these obstructions. The sequelae include fever, acute pyelonephritis, chronic renal inflammation, and death. We hypothesize d that even brief obstruction of the urinary tract containing a nonvir ulent bacterium would result in these complications. Mice challenged t ransurethrally with Escherichia coli FN414, which is rapidly eliminate d from normal mice without causing bacteriuria, bacteremia, or renal p athology, were subjected to reversible urethral obstruction by coating the urethral meatus with collodion for 1, 3, or 6 h. The majority of mice obstructed for 1 h demonstrated parenchymal renal inflammation 48 h later. At the end of 3 h of obstruction, 9 of 10 mice were bacterem ic; some bacteremias were present at 48 h after removal of the obstruc tion. At that time, more severe renal inflammation was seen in these m ice. As little as 6 h of obstruction resulted not only in the acute ch anges described above but also in chronic renal inflammation and fibro sis in the majority of animals sacrificed 3 and 6 weeks later. Additio nal studies demonstrated that urethral obstruction enhanced the uropat hogenicity of another nonpathogenic E. coli strain (K-12 strain HB101) and caused more severe renal lesions in mice challenged with E. coli CFT073, isolated from a patient with symptoms of pyelonephritis. These findings demonstrate that brief urethral obstruction may (i) induce o rganisms which are cleared rapidly from the normal urinary tract to ca use bacteriuria, bacteremia, and pyelonephritis and (ii) intensify the renal lesions caused by a uropathogen.