Submitted to: Sensors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2009
Publication Date: 1/29/2009
Citation: Tu, S., Reed, S.A., Gehring, A.G., He, Y., Paoli, G. 2009. Capture of E. coli O157:H7 using immunomagnetic beads of different size and antibody conjugating chemistry. Sensors. 9:717-730. Interpretive Summary: Due to recent high profile outbreaks of E. coli O157:H7 in spinach (CDC) and Salmonella Saintpaul (CDC), the safety of our food has been of highest concern. From the farm where the food is produced, to the handling practices of manufacturers, to our own kitchens, food safety involves all stages of food production and consumption. Therefore, the need not only for the eradication of food-borne pathogens exists, but also their rapid and sensitive detection once they enter the food chain. Conventional selective enrichment and serological tests of the E. coli take 5-7 days and are labor intensive. We have developed a rapid and sensitive approach that involved the capture of E. coli by imunomagnetic beads and then followed by detection of captured E. coli by a very sensitive time-resolved fluorescence (TRF) method. We also demonstrated that the capture of E. coli in ground beef 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 E. coli O157:H7 in foods.
Technical Abstract: Immunomagnetic beads (IMB) were synthesized using anti-E. coli O157 antibodies and magnetic beads of two different sizes (1 'm and 2.6 to 2.8 'm) that contained streptavidin coating, activated carboxyl groups or tosylated surfaces. The synthesized IMB together with a commercially available IMB were applied to capture different strains of E. coli O157:H7 and E. coli O157:NM. The E. coli capture was measured by the time resolved fluorescence (TRF) intensity using a sandwich assay. The analyses of measured TRF intensity and determined antibody surface concentration, indicated that larger beads provided higher response signals than smaller beads and were more effective in capturing the target of interest in pure culture and ground beef. In addition, while each type of IMB showed different favorable capture of E. coli O157:H7, streptavidin-coated IMB elicited the highest response, on average. Streptavidin-coated IMB also provided an economic benefit, costing less than the other IMB per assay. The results could be used to guide the proper choice of IMB for applications in developing detection processes for E. coli O157:H7.