Judy Keller
ATLANTA, GA—Repeated outbreaks of deadly meat contamination spurred Georgia Tech Research Institute scientists to develop a sensor that quickly detects E. coli, salmonella and other foodborne pathogens.
The biosensor is a tiny bacterial sensing device that can identify simultaneously any of a dozen disease-causing agents or pathogens and measure the degree of concentration in two hours, not days. And its cost is lower than current laboratory methods, claims research engineer Nile Hartman, a biosensor developer and senior research engineer at Georgia Tech.
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“The biosensor will help in quality control in food processing plants,” says biosensor collaborator Dr. Paul Edmonds, a professor of biology at Georgia Tech. “It would minimize the chance of contamination of the final product.”
A researcher performs a biosensor test at a Georgia poultry plant. Photo courtesy of Georgia Institute of Technology.
At a cost of $1,000 to $5,000, the biosensor is cheaper than current lab equipment for food testing, which can cost about $20,000, Hartman says.
The Georgia Tech researchers collaborated with Dr. Robert Brackett, professor at the University of Georgia's Center for Food Safety and Quality Enhancement, and have been developing and testing the biosensor for about four years. They are preparing for a field test, slated to begin in January 2000, at the Gold Kist plant in Carrollton, GA. The first tests will be done on poultry.
While lab tests show the biosensor can detect pathogens at minute levels of 500 cells per milliliter, researchers are hopeful they can improve that sensitivity to 100 cells per milliliter.
Current lab methods achieve sensitivity levels of 5,000 cells per milliliter, and take 8 to 24 hours to yield results.
The first phase of the field test will last three to six months, and will have researchers comparing field and lab results.
Hartman says the biosensor can detect 12 pathogens, but that researchers are concentrating on this list: Salmonella, E. coli 0157:H7, generic E. coli, Listeria monocytogenes, Campylobacter jejuni, and Yersenia enterocolitica. Most of these pathogens are found in meat, but can sometimes occur in produce.
The biosensor uses integrated optics, immunoassay techniques and surface chemistry tests. It indirectly detects pathogens by combining immunoassays with a chemical sensing scheme. Antibodies specific for antigens of particular pathogens are chemically bound to the instrument's waveguide.
Urease enzymes are coupled with antigens that react with antibodies. Then urea is added to produce gaseous ammonia. The chemical sensor detects the ammonia, affects the properties of the sensor, and signals changes in transmitted laser light. These changes reveal both the presence and concentration of specific pathogens.
Competing with the biosensor are other testing techniques under development. One is an electrochemical method and another is a DNA-based method called PCR, which is extremely sensitive but time consuming.
Hartman and the Georgia Tech Research Corp. patented the optic interferometric sensor technology upon which the biosensor is based. It is also the basis for a chemical contaminant sensing system call E-Smart.