Salmonella Enteritidis experimental infection in chickens: Effects of challenge dose on serum immunoglobulin G antibody response

Salmonella enterica serovar Enteritidis is a food borne pathogen of humans causing food-poisoning and sometimes deaths. In order to control egg-borne transmission of Salmonella Enteritidis to humans, prompt and accurate detection of infected poultry flocks is essential. This paper examined the effects of challenge dose of Salmonella Enteritidis on detection of specific immunoglobulin G (IgG) antibody in serum of experimentally infected chickens. An indirect ELISA technique based on lipopolysaccharide (LPS) antigen of Salmonella Enteritidis was used. Two groups of specific-pathogen-free chickens were infected orally with 10(8) and 10(4) colony forming units (cfu) of Salmonella Enteritidis. Serum samples were collected prior to challenge and at five subsequent weekly intervals. Levels of serum IgG antibody response observed in the chickens infected with 10(8) cfu of Salmonella Enteritidis were significantly stronger (P<0.05) than those of the 10(4) cfu group. Although considerable IgG response was seen with most of the chickens by 2 weeks post-infection, highest group mean optical density values of 2.177 and 0.984 were observed at 5 weeks for 10(8) and 10(4) cfu Salmonella Enteritidis infected groups, respectively. Chickens exposed to few Salmonella colonies during infection do not produce high IgG antibody and may continue to contaminate the flock.