Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2002
Publication Date: 8/8/2002
Citation: Gast, R.K., Nasir, M.S., Jolley, M.E., Holt, P.S., Stone, H.D. 2002. Detection of experimental salmonella enteritidis and s. typhimurium infections in laying hens by fluorescence polarization assay for egg yolk antibodies. Poultry Science.
Interpretive Summary: Detecting infected poultry flocks is important for preventing egg-borne transmission of Salmonella to humans. This study evaluated the ability of a rapid fluorescence polarization (FP) test to detect antibodies in egg yolks from chickens infected experimentally with S. enteritidis (SE) or S. typhimurium (ST). 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 a traditional enzyme immunoassay (ELISA). When applied to yolk samples from laying hens inoculated with two different dose levels of SE, the FP assay (using O-polysaccharide tracers from SE) detected infection as often as did ELISA (using an SE flagella antigen). Also, the FP tests gave fewer potentially misleading cross-reactions with sera from hens infected with ST, although a substantial degree of cross-reaction was observed with all tests. The FP test appears to be a rapid and effective alternative to ELISA, although serological assays may be prone to non-specific detection of infection with other Salmonella serotypes.
Technical Abstract: This study evaluated a rapid fluorescence polarization (FP) assay for use in identifying laying chickens infected with Salmonella enteritidis (SE) and S. typhimurium (ST). Egg yolk samples from experimentally infected hens were tested for specific antibodies by FP assays using tracers prepared from the O-polysaccharides of SE and ST and by a conventional ELISA using an SE flagellin antigen. Groups of specific-pathogen-free laying hens were infected orally with either 1 million or 100 million cfu of SE (phage type 13a) or with 100 million cfu of ST. Eggs were collected during 5 weekly post-inoculation intervals. Both FP and ELISA detected the majority of hens infected with SE at either dose level, although they also frequently cross-reacted with samples from hens infected with ST. FP using an ST tracer was likewise able to consistently detect ST infection but also tended to cross-react with samples from hens infected with SE. FP appears to offer a simple and rapid alternative to conventional serological methodology, although concerns about specificity may limit the usefulness of antibody testing data.