Use of light addressable potentiometric sensor (LAPS) to detect magnetically captured Escherichia coli O157:H7 in ground beef

Shu-I Tu; Joseph Uknalis; Peter L. Irwin; Linda S. L. Yu

doi:10.1117/12.418716

13 March 2001 Use of light addressable potentiometric sensor (LAPS) to detect magnetically captured Escherichia coli O157:H7 in ground beef

Shu-I Tu, Joseph Uknalis, Peter L. Irwin, Linda S. L. Yu

Author Affiliations +

Proceedings Volume 4206, Photonic Detection and Intervention Technologies for Safe Food; (2001) https://doi.org/10.1117/12.418716
Event: Environmental and Industrial Sensing, 2000, Boston, MA, United States

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.

Citation Download Citation

Shu-I Tu, Joseph Uknalis, Peter L. Irwin, and Linda S. L. Yu "Use of light addressable potentiometric sensor (LAPS) to detect magnetically captured Escherichia coli O157:H7 in ground beef", Proc. SPIE 4206, Photonic Detection and Intervention Technologies for Safe Food, (13 March 2001); https://doi.org/10.1117/12.418716

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