A rapid strip immunoblot assay for the specific detection of Salmonella enteritidis infection in chickens

A rapid strip immunoblot assay (RSIA) was developed using recombinant SEF14 antigen. The rSEF14–RSIA was very specific in detecting antibodies to Salmonella enteritidis in chickens. When serum samples obtained from groups of chickens (N=5) inoculated with six different Salmonella serovars were tested in rSEF14–RSIA, only serum samples obtained from S. enteritidis inoculated birds reacted with rSEF14 antigen except for a group of chickens that had been inoculated with S. dublin. To assess the sensitivity of the rSEF14–RSIA, groups of chickens were inoculated with either 104 cfu or 1010 cfu of S. enteritidis and the serum and egg yolk were analyzed for SEF14 antibodies. By 1 week after infection 66–78% of chickens were found positive for SEF14 antibodies in the serum and the number of positive birds increased subsequently to 89–100%. The S. enteritidis specific antibodies appeared as early as 6 days after infection in the egg yolk of infected chickens. The antibodies to SEF14 in both the serum and egg yolk persisted for at least 7 weeks after infection in a significant proportion of chickens. Our results suggest that rSEF14–RSIA can be a practical and efficient screening test for identifying S. enteritidis infected chickens.