Translocation and Fate of 32 P-Labeled Salmonella in Mice 1

Summary

The translocation and fate of both ³²P-labeled and unlabeled Salmonella enteritidis in mice fed, by gavage, 1 ml containing 10⁸ cells of either an 18-hr or 36-hr-old culture was determined. Onset and duration of infection and the presence of viable cells of test culture in organs were confirmed by bacterial and radioisotope analyses. Mice fed 10^{8 32}P-18-hr culture had low specific activity on 2nd hr PF (liver, 72; spleen, 61; and cecum, 1480 counts min^-1 mg^-1 of tissue) increasing to 147, 103, and 2110, respectively, on 6th hr. Mice infected with ³²P-36-hr culture showed high specific activity (counts min^-1 mg^-1 of tissue) on 2nd hr postfeeding; liver, 328; spleen, 227; and cecum, 11,170 followed by a rapid decrease to 234, 216, and 4820 counts min^-1 mg^-1 of tissue on 6th hr, respectively. This radioisotope study indicated that the 18-hr-old culture was more invasive than the 36-hr culture. Ultrathin sections of duodenum, obtained from infected mice, and stained with fluorescent antibodies revealed the presence of high fluorescent bacterial cells having a retention time of 3 min similar to that of pure S. enteritidis cells. Histopathologically these sections showed regressive changes in surface epithelium of intestinal mucosa of mice fed 18-hr culture and coagulation necrosis was common at tip of the villi. The pathological data showed that 18-hr culture produced a more severe enteritis compared to 36-hr-old culture.