Submitted to: Journal of Food Analytical Methods
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/12/2010
Publication Date: 11/4/2010
Citation: Tu, S., Reed, S.A., Gehring, A.G., He, Y. 2010. Simultaneous detection of Escherichia coli O157:H7 and Salmonella Typhimurium: The use of magnetic beads conjugated with multiple capture antibodies. Journal of Food Analytical Methods. DOI 10.1007/s12161-010-9175-z. Interpretive Summary: According to the estimation of Center of Disease Control and Prevention, each year outbreaks of food-borne pathogens result in 76 million cases of illness, more than 300,000 hospitalizations and 5,000 deaths. Current microbiological methods for pathogen detection are time consuming and expensive. Thus, there is a need to develop rapidly, effectively and accurately alternative approaches to detect the presence of pathogens in foods. To meet this goal, we have developed an approach involving the use of immunomagnetic beads (IMB) for pathogen capture followed by sensitive detection using a method called time-resolved fluorescence (TRF). In current study, we devised a new approach to equip the IMB with dual antibodies and thus capable of capturing both E. coli O157:H7 and Salmonella. Applications of this new IMB enable the capture and detection of the two pathogens simultaneously from ground beef and spinach samples. This cost-saving and effective pathogen capture and detection process will be of value to regulatory agencies.
Technical Abstract: Streptavidin-coated magnetic beads were conjugated with biotinylated capture antibodies to both Escherichia coli O157:H7 and Samonella Typhimurium to form multi-pathogen capture immunomagnetic beads (IMB-M). The efficacy of these beads was investigated and compared to the use of a mixture of IMB against the E. coli (IMB-E) and the Salmonella (IMB-S) in both pure and mixed culture suspensions, as well as spiked spinach and ground beef samples. Dual-label time-resolved fluorescence (TRF) was employed as the means of detection post-capture. A sandwich immunoassay consisting of europium- and samarium-labeled detection antibodies were used to measure the capture of E. coli and Salmonella, respectively. While the IMB-M did not elicit signals as high as those of other capture methods in pure and mixed culture suspensions, the detection limit was comparable. In spiked food samples, the IMB-M combined with TRF was just as effective at detecting 1 cfu/g of E. coli O157:H7 and 100 cfu/g of Salmonella Typhimurium in 6 hours as a mixture of IMB specific for both target organisms. Multi-pathogen capture IMBs have the potential to be convenient and important tools for multi-pathogen detection.