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ARS Home » Research » Publications at this Location » Publication #193064


item Geng, Tao
item Uknalis, Joseph
item Tu, Shu I
item Bhunia, Arun

Submitted to: Sensors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2006
Publication Date: 8/19/2006
Citation: Geng, T., Uknalis, J., Tu, S., Bhunia, A. 2006. Fiber-optic biosensor employing alexa-fluor conjugated antibody for detection of escherichia coli 0157:h7 from ground beef in four hours. Sensors. 6:796-807

Interpretive Summary: The Centers for Disease Control have estimated that E. coli O157:H7 bacteria cause 73,000 cases of serious illness and 61 deaths in the United States each year. Most illness has been associated with eating of undercooked, contaminated ground beef. There is an urgent need for sensitive, specific and rapid detection of this bacteria. We have developed a new assay based on a commercially-available, portable fiber optic biosensor. This assay is very specific for E. coli O157:H7 and can detect very low levels of the bacteria in ground beef within 5 hours. Higher levels of contamination can be detected in even less time. The biosensor and battery pack can be carried in a briefcase, allowing assays to be performed at the farm, processing plant, distribution center, and retail store. This capability provides the food industry and regulatory agencies a powerful new tool to combat foodborne disease and bio-terror threats.

Technical Abstract: Fiber optic biosensor has a great potential to meet the need for rapid, sensitive, and real-time microbial detection systems. We developed an antibody-based fiber-optic biosensor to rapidly detect low levels of Escherichia coli O157:H7 cells in ground beef. The principle of the sensor is a sandwich immunoassay using an antibody which is specific for E. coli O157:H7. A polyclonal antibody was first immobilized on polystyrene fiber waveguides through a biotin-streptavidin reaction served as a capture antibody. An Alexa Fluor 647 dye-labeled antibody to E. coli O157:H7 was used to detect cells and generate a specific fluorescent signal, which was acquired by launching a 635 nm laser-light from an Analyte-2000. Fluorescent molecules within several hundred nanometers of the fiber were excited by an evanescent wave, and a portion of the emission light from fluorescent dye transmitted by the fiber and collected by a photodetector at wavelengths of 670 to 710 nm quantitatively. This immunosensor was specific for E. coli O157:H7 compared with multiple other foodborne bacteria. In addition, the biosensor was able to detect as low as 103 CFU/ml pure cultured E. coli O157:H7 cells grown in BHI. Artificially inoculated E. coli O157:H7 at concentration of 1 CFU/ml in ground beef could be detected by this method after only 4 hours of enrichment.