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Proceedings Paper

Use of light addressable potentiometric sensor (LAPS) to detect magnetically captured Escherichia coli O157:H7 in ground beef
Author(s): Shu-I Tu; Joseph Uknalis; Peter L. Irwin; Linda S. L. Yu
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Paper Abstract

An improved process using magnetic capture of antibody-conjugated bacteria for light addressable potentiometric sensor detection by the Threshold instrument was developed. Cells of Escherichia coli 0157:H7 were captured by the biotinylated anti-E. coli 0157 antibodies conjugated to streptavidin coated magnetic beads. Magnetically concentrated bacteria were further labeled with by fluorescein-conjugated anti-E. coli 0157 antibodies that were bound to urease-conjugated antifluorescein antibody. The whole bacteria-containing complex was then immobilized on 0.45? biotinylated nitro-cellulose membranes via streptavidin-biotin interactions. The rates of pH change associated with the production of NH3 by conjugated urease were measured by a LAPS technique incorporated in the Threshold instrument. This approach allowed us to detect io CFU of cultured E. coli 0157:H7 in tris-buffered saline (TBS). The same approach was applied to detect the E. coli in beef hamburger spiked with the bacteria. After a 5 to 6-hour enrichment, as low as 1 CFU/g of E. coli 0157:H7 in the hamburger could be detected. In addition, the immobilized bacterial complexes on the nitro-cellulose membranes exhibited a stability longer than 48 h at 4 and 22 °C in TBS allowing the possibility of conveniently shipping collected samples rather than raw beef to testing laboratories.

Paper Details

Date Published: 13 March 2001
PDF: 6 pages
Proc. SPIE 4206, Photonic Detection and Intervention Technologies for Safe Food, (13 March 2001); doi: 10.1117/12.418716
Show Author Affiliations
Shu-I Tu, U.S. Department of Agriculture (United States)
Joseph Uknalis, U.S. Department of Agriculture (United States)
Peter L. Irwin, U.S. Department of Agriculture (United States)
Linda S. L. Yu, U.S. Department of Agriculture (United States)


Published in SPIE Proceedings Vol. 4206:
Photonic Detection and Intervention Technologies for Safe Food
Yud-Ren Chen; Shu-I Tu, Editor(s)

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