Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/1999
Publication Date: 5/8/2000
Interpretive Summary: Serological surveillance can be an important component for egg quality assurance programs geared toward controlling Salmonella enterica serovar Enteritidis (S. enteritidis) problems within a flock. Serum is the primary sample source for the procedures although egg yolk antibody assays have achieved a certain degree of popularity in recent years. However, these assays tend to be labor intensive, requiring procedures for extracting antibodies from the yolk followed by the performance of the assays themselves. We describe an adaptation of the agar gel precipitin (AGP) test for use in detecting antibodies to S. enteritidis deposited in egg yolks of infected hens. Yolk can be applied directly to wells in an agarose plate and specific S. enteritidis antibodies in the yolk will migrate into the agarose and react with S. enteritidis migrating from other wells. Where the antibodies and S. enteritidis react, a line will form which is visible to the naked eye. The assay worked as well as standard S enteritidis antibody tests but did not require the sample processing or complicated procedures necessary for the other assays. The simplicity of the AGP and low requirements for sophisticated equipment make this test a potentially useful tool for individuals conducting serological surveillance of their flocks.
Technical Abstract: Serological surveillance can be an important component for egg quality assurance programs geared toward controlling Salmonella enteritidis problems within a flock. We describe an adaptation of the agar gel precipitin (AGP) test for use in detecting antibodies to S. enteritidis deposited in egg yolks of infected hens. Yolk or sera from infected birds swas administered to wells cut into seven-well clusters in an agar gel plat & detection antigen was added to the center well. The agar gels were incubated for 24 hours & then examined for the presence of precipitin lines formed by the interaction of antibody with antigen. 3 different antigens were tested: S. enteritidis flagella, SEF14 (a 14 kDa fimbrial protein produced ostensibly by S. enteritidis) & a sodium deoxycholate extract of whole S. enteritidis organism. Flagella & the organism extract detected antibodies to S. enteritidis in the yolk and sera while SEF14 was not reactive. Positive reactions were observed in serum 1 wk post challenge while in yolks, this was delayed further by one week. Simplicity & low labor requirements of the assay would allow for the potential testing of several hundred egg samples within a day which would make up for test shortcomings due to sensitivity. The AGP test could be an important tool for individuals using serological testing to monitor the S. enteritidis situation within their flocks or as a rapid screen for vaccine responses.