An ascending non-obstructive model for chronic pyelonephritis in BALB/c mice.

Chronic pyelonephritis was successfully produced in female BALB/c mice with Escherichia coli after introduction of the bacterial inoculum by the ascending route. E. coli strain 31-B, a nalidixic acid-resistant derivative of strain TN675 expressing type-1 pili, and E. coli strain BH-5, a mutant of 31-B, not expressing type-1 pili, were used in the model. Both the strains were able to induce chronic renal inflammation in the experimental animals. Whereas the initial colonisation was greater with strain 31-B, its non-pilate mutant BH-5 caused a significantly greater inflammatory response and also caused renal scarring observable 5 months after the infection.