ExperimentalEscherichia coli pyelonephritis: Formation of spheroplasts in the kidney of the untreated rat

An experimental hematogenous pyelonephritis produced in the rat byEscherichia coli was studied from the point of view of the possible rôle of L-forms of bacteria in chronic renal infection. Osmotically fragile cells were shown in the kidneys from the 3rd day after inoculation, and their percentage of the totalE. coli cell number increased during the course of the infection. In order to distinguish bacteria and spheroplasts of theE. coli strain used, two more methods were elaborated: 1) a bacteriological method based on the different sensitivity of bacteria and spheroplasts to erythromycin; this method confirmed the results obtained with osmotic shock; 2) an immunological method, using the indirect fluorescent antibody technique and an antiserum specifically labelling the spheroplasts; in kidneys removed 10–15 days after the inoculation, spherical bodies with morphological and antigenic characteristics similar to those of spheroplasts became visible.