Submitted to: Journal of Food Analytical Methods
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/22/2008
Publication Date: 6/25/2008
Citation: Tu, S., Reed, S.A., Gehring, A.G., He, Y. 2008. Detection of Salmonella Enteriditis from Egg Components Using Different Immunomagnetic Beads and Time-resolved Fluorescence. Journal of Food Analytical Methods. Available:http://www.springerlink.com/content/68381p3740355j10/ Interpretive Summary: The U.S. Department of Agriculture has estimated that per capita consumption of eggs in America is now about 260. According to the Center for Disease Control and Prevention, however, consumption of Salmonella Enteritidis (SE) contaminated raw or undercooked eggs has led to about 118,000 cases of illness yearly. This health concern has prompted the needs of developing fast, specific and sensitive methods to detect the presence of SE in eggs. Conventional selective enrichment and serological tests of Salmonella, including SE from eggs take 5-7 days and are labor intensive. We have developed a rapid and sensitive approach that involved the capture of SE by imunomagnetic beads and then followed by detection of captured SE by a very sensitive time-resolved fluorescence (TRF) method. We also demonstrated that the capture of SE in whole egg, egg white and egg yolk varied by the different types of immnunomagnetic beads applied. The information is valuable for regulatory agencies and food safety laboratories to develop practical, automated and bead-based methodologies to detect SE in eggs.
Technical Abstract: The types of chemical linkage used to link antibodies to magnetic beads to form immunomagnetic beads (IMB) were compared in the capture and detection of Salmonella Enteriditis from egg components. Egg components were inoculated with outbreak strains of S. Enteriditis. After incubation under different conditions, IMBs derived from linking antibodies to core magnetic beads via biotin-streptavidin interactions, Schiff-base bonds and unspecified proprietary chemistry were used to capture S. Enteriditis. Europium-labeled anti-Salmonella antibodies completed the sandwich, and time-resolved fluorescence served as the means of detection. For the Salmonella cultured from UPB, the detection signal intensity was affected by the chemistry utilized to link the antibodies to IMB. Relative to UPB, much lower detection signals were detected in cultures obtained from egg components. Egg yolk proved to be as good as UPB in supporting the growth of S. Enteriditis, but not egg white. For cultures obtained from egg yolks, the low detection signals by all IMBs suggesting the accessibility of the antigenic groups to the antibodies on IMBs was reduced. The addition UPB to egg white restored the growth of Salmonella and yielded stronger detection signals than that obtained from cultures obtained from UPB with egg yolk. For the same cultures, the detection signal intensity obtained by different IMBs varied considerably. The results suggested that the intensity of detection signal was affected by the linking mechanism used for conjugating the antibodies to the magnetic beads. Presumably, the linkage might affect the interactions of the antibodies to the antigenic groups on the bacteria.