Georgia Tech Research News - September 1999
Food Safety: Biosensor that detects pathogens in poultry and other foods
to be tested in Metro Atlanta processing plant
 Recent incidences of contaminated meat in grocery stores and restaurants
have heightened consumer concern. But people who eat meat may rest
easier if a new bacterial sensing device to be field tested this fall delivers
the accurate and speedy results, plus the low costs its developers
predict.
The device, called a biosensor, was developed at the Georgia Tech Research
Institute (GTRI). It can simultaneously identify species and determine
concentrations of multiple pathogens -- including the deadly E. coli 0157:H7
and Salmonella
-- in food products in less than two hours while in operation on a
processing plant floor.
The most significant advantage of the biosensor is the time reduction
in assessing the presence of contamination, said Nile Hartman, a biosensor
developer and senior research engineer at GTRI.
Lab tests for E. coli and Salmonella in meat are required by federal
regulators, but there are no standards for bacterial concentration.
Most companies perform laboratory tests, but they are costly and slow
-- sometimes
not even yielding results for 48 to 72 hours. That delay requires that
food products remain stored in warehouses for longer periods.
 The biosensor will help in overall quality control in food processing
plants, said collaborator Dr. Paul Edmonds, a professor of biology
at Georgia Tech. It would minimize the chance of the final product being
contaminated.
Georgia Tech researchers -- in collaboration with Dr. Robert Brackett,
a professor at the University of Georgia's Center for Food Safety and
Quality Enhancement in Griffin -- have been developing and testing the
biosensor
in their laboratories for about four years. Now they are ready for
a field test expected to start in November at Gold Kist in Carrollton,
Ga., just
west of Atlanta.
Laboratory tests have proven the biosensor is extremely sensitive,
meaning it can detect pathogens at minute levels of 500 cells per milliliter.
Researchers
believe they can improve that sensitivity to 100 cells per milliliter.
Current laboratory methods only achieve sensitivity levels of 5,000 cells
per milliliter,
and they usually take from eight to 24 hours to yield results. In addition,
lab equipment costs $12,000 to $20,000 per instrument compared to an
estimated $1,000 to $5,000 for a biosensor.
But before the biosensor gains market acceptance, it must prove its
effectiveness in the upcoming field test. The first phase will last three
to six months,
and researchers will be comparing their biosensor test results with
the company's lab findings.
One of the things we will be looking at is reproducability of results,
Hartman said. We will split a sample for testing with both of the technologies
(the biosensor and lab tests). For every 1,000 tests we do, we will
look for the variation between results of the two methods.
The biosensor can simultaneously detect 12 different pathogens, but
researchers are concentrating on six bacterial species for now. They are
Salmonella,
E. coli 0157:H7, generic E. coli, Listeria monocytogenes, Campylobacter
jejuni and Yersenia enterocolitica (found primarily in red meat). All
of these pathogens are associated with stomach illness in humans. When
detected,
they are usually found in meat, but sometimes they occur in produce.
The biosensor operates with three primary components -- integrated
optics, immunoassay techniques and surface chemistry tests. It indirectly
detects
pathogens by combining immunoassays with a chemical sensing scheme.
In the immunoassay, a series of antibodies selectively recognize target
bacteria.
The "capture" antibody is bound to the biosensor and catpures
the target bacteria as it passes nearby. A set of "reporter" antibodies,
which bind with the same target pathogen, contain the enzyme urease, which
breaks down urea that is then added and produces ammonia. The chemical sensor
detects the ammonia, affecting the optical properties of the sensor and
signaling changes in transmitted laser light. These changes reveal both
the presence and concentration of specific pathogens in a sample at extremely
minute levels.
If pathogens are found with the biosensor, then food processors can
make decisions more quickly about applying treatments, such as antiseptics,
Edmonds
said. Or they might divert those products to cooking operations, which
would kill the pathogens. And companies could modify their sanitation
plans.
The field test is expected to demonstrate the biosensor's ability to
improve food processors' operations, but it has some competition from
other techniques. One that is under development is an electrochemical
scheme that
can reportedly detect pathogens at 100 to 1,000 cells per milliliter.
Another technique already in use is a DNA-based method called PCR. While
extremely
sensitive, it is very time-intensive in terms of sample preparation.
Meanwhile, the integrated optic interferometric sensor technology upon
which the biosensor is based has already been patented by Hartman and
the Georgia Tech Research Corporation. It is also the basis for a chemical
contaminant
sensing system called E-SMART. That system is also undergoing field
tests. The chemical sensor was licensed commercially by the Atlanta-based
company
Photonic Sensor.
Commercialization for the biosensor is still some time away, researchers
said. After the field test at Gold Kist is completed, researchers plan
to return to their laboratories to further refine the technology. "We
would like to extend the biosensor's capabilities to detect other pathogens,
and we will need to optimize the chemistry for that," Hartman said. "Also,
we would like to use the biosensor to address other food safety issues,
such as those associated with insecticides, pesticides and growth hormones."
In addition to its application in the poultry and beef industries,
Edmonds believes there is a need for the biosensor in the seafood industry.
It contends
with a variety of waterborne pathogens, particularly in shellfish.
And the dairy industry could benefit from biosensor use, as well, he said.
An outbreak
of Listeria was found in Brie cheese several years ago.
While biosensor development continues, the state-funded Agricultural
Technology Research Program at Georgia Tech is sponsoring the project.
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