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 10(4) cfu or 10(10) 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.