Comparison of four different enzyme-linked immunosorbent assays for serological diagnosis of Salmonella enteritidis infections in experimentally infected chickens

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Abstract
The program for the eradication of Salmonella enteritidis from chickens in The Netherlands is based on bacteriological examination of breeding flocks. There is a great need for a specific and sensitive serological screening test. For that purpose, we developed four different enzyme-linked immunosorbent assays (ELISAs), i.e., an indirect ELISA with S. enteritidis flagellin, an indirect ELISA with S. enteritidis lipopolysaccharide, a double-antibody sandwich blocking ELISA that uses monoclonal antibodies against S. enteritidis flagellin (GM-DAS blocking ELISA), and a double-antibody sandwich ELISA that uses monoclonal antibodies against S. enteritidis lipopolysaccharide. In the present study, we compare the results of those ELISAs with sera from experimentally infected 1-day-old chickens and with sera and eggs from experimentally infected laying hens. Experimental infections were induced with strains of S. enteritidis phage types 1 and 2, S. typhimurium, and S. panama. Sera were collected up to days 44 and 39 after infection from 1-day-old chickens and laying hens, respectively. Only the GM-DAS blocking ELISA was able to discriminate between S. enteritidis infections and infections with the other serotypes. This ELISA had both a sensitivity and a specificity of 100% for all serum samples from experimentally infected chickens. A field study is in progress to evaluate whether this test can be implemented in the Dutch S. enteritidis eradication program.