Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2001
Publication Date: 3/6/2002
Citation: Gast, R.K., Nasir,, M.S., Jolley,, M.E., Holt, P.S., Stone,, H.D. 2002. Serological detection of experimental salmonella enteritidis infections in laying hens by fluorescence polarization and enzyme immunoassay. Avian Diseases. Interpretive Summary: Detecting infected poultry flocks is essential for controlling egg-borne transmission of Salmonella enteritidis to humans. This study evaluated the ability of a fluorescence polarization test to detect antibodies in the blood of chickens infected experimentally with S. enteritidis. Based on changes in the rate at which a tracer molecule spins in solution after binding with specific antibodies, this assay is faster and simpler than traditional enzyme immunoassay (ELISA). When applied to serum samples from laying hens inoculated with two different dose levels of S. enteritidis, the fluorescence polarization assay (using an O-polysaccharide tracer) detected infection more often than an ELISA test (using a flagella antigen). Also, the fluorescence polarization test gave fewer potentially misleading cross-reactions with sera from hens infected with S. typhimurium.
Technical Abstract: The present study evaluated the sensitivity and specificity of detection of antibodies in the sera of experimentally infected chickens by a fluorescence polarization assay using a tracer prepared from the O-polysaccharide of S. enteritidis and an ELISA using an S. enteritidis flagellin antigen. In two trials, groups of specific-pathogen-free laying hens were infected orally with either 1 million or 100 million CFU of S. enteritidis (phage type 13a) or with 100 million CFU of S.typhimurium. Serum samples were collected before inoculation and at 5 subsequent weekly intervals. Both assays successfully detected the majority of hens infected with S. enteritidis at either dose level, but they also identified a substantial number of hens infected with S. typhimurium as seropositive. The fluorescence polarization test detected S. enteritidis infection significantly more often and cross-reacted with sera from hens infected with S. typhimurium significantly less often than the ELISA. The fluorescence polarization assay also offered advantages in terms of speed and methodological simplicity.