Hematogenous Streptococcus faecalis pyelonephritis in the rat. A histologic, immunopathologic and bacteriologic study.

The demonstration of bacterial antigens in active pyelonephritis in man has been inconsistent. In this paper we have studied 110 rats with experimental pyelonephritis induced by a single intravenous injection of Streptococcus faecalis. The animals were studied at intervals up to 1 year; bacteremia, urine and renal parenchymal bacterial counts were monitored. In these animals it was observed that bacteriuria and positive bacterial cultures of renal tissue persisted up to 1 year in some rats. Bacteria and their antigenic products in small foci were detected by immunofluorescence in the pyelonephritic lesions. The highly focal distribution of the bacterial antigens in bacteriologically positive tissues of this model suggest the need for careful fixation technics, availability of large tissue specimens and careful control of immunologic factors. These specific requirements to detect bacterial antigens may preclude the practical study of human pyelonephritic kidneys.