Salmonella Enteritidis detection and immunological cellular response to experimental inoculation in day-old turkeys

Abstract

The purpose of this research is to clarify aspects of the pathogenesis of Salmonella Enteritidis in experimentally inoculated day-old turkeys. Three treatments were conducted among a total of 120 turkeys; one control group and two treatment groups in which 6 x 102 CFU mL-1 and 7 x 105 CFU mL-1, respectively, of Salmonella Enteritidis was inoculated in the crops. Two birds from each treatment were sacrificed and necropsied at 1, 3, 4, 12, 18, and 24 hours, and 3, 4, 38, and 49 days post-inoculation. We re-isolated Salmonella, measured lymphocytes, and conducted immunohistochemical tests. Six hours post-inoculation, Salmonella was found in the investigated organs (yolk sac, cecum, fragments of spleen, and bursa of Fabricius) with conventional bacteriology and immunohistochemistry, and was continuously detected in almost all analyzed organs until turkeys were four-days old. Further, Salmonella was detected after 38 days in cecum, when the concentration 7 x 105 CFU mL-1 was given. At both inoculation concentrations, the number of lymphocytes was similar; larger quantities were found in the first hour post-inoculation, followed by a gradual reduction, reaching the lowest levels at 24 hours after inoculation. Afterwards, lymphocytes increased discreetly, remaining at the same level until 49 days after inoculation. In conclusion, inoculation concentration influences mitigation, dissemination, elimination, and persistence of this pathogen in turkeys. Lower concentrations promote less invasion as well as lower cell stain and lower lymphocyte count.