Experimental pyelonephritis in mice following ascending infection with E. coli. Chronic phase.

Adhesive and invasive strains of Escherichia coli induced chronic pyelonephritis in mice following the acute phase. The pathological features of the induced chronic pyelonephritis were different between the groups of mice infected with these strains. In piliated adhesive strain (E77156)-infection, the kidneys with viable bacilli showed pyonephrosis with incomplete obstruction or atrophy with coarse scar. Mice with these renal lesions showed high serum antibody levels, but histologically recurrent infection was frequent. On the other hand, in non-piliated invasive strain (633-65)-infection, sterile pyelonephritis developed. This chronic lesion was characterized by the migration of antigen-bearing macrophages and lymphocytes and by a negative serum antibody response. In infections with either strain the predominant lymphocytes in the renal lesions were smooth-surfaced T-lymphocytes.