THE 1993 FOOD POISONING DEATHS of several Washington state children who ate tainted hamburgers are sobering evidence of the problems food contamination can pose. Rapid detection of dangerous bacteria, such as the organisms that resulted in the Washington state deaths, is essential in the nation's efforts to prevent the spread of food-borne pathogens.

This sensor incorporates integrated optics, immunoassay techniques and surface chemistry skills to detect salmonella bacteria in meat in a fraction of the time required by other methods.

To that end, researchers at Georgia Tech are developing a modestly priced, rapid-response biosensor for detecting microbial quality -- and it will revolutionize the way dangerous food- borne pathogens are detected. The sensor uses laser-based technology to find salmonella bacteria in meat in a fraction of the time usually required.

Nile Hartman, a principal research engineer in GTRI, Dr. Paul Edmonds, an associate professor of biology, and Dr. Dan Campbell, a research scientist in GTRI, collaborated with three companies to develop a device that soon will be inexpensive enough to be used by any local poultry plant. The biosensor incorporates integrated optics, immunoassay techniques and surface

chemistry skills. Laser-based technology allows the sensor to detect salmonella bacteria in meat in a fraction of the time required by other methods. The rapid-response biosensor's ability to detect pathogens is based on the fact that the speed of light increases or decreases when passing through materials of differing optical properties, says Hartman.

"Direct detection of bacteria becomes possible by measuring the organism's influence on the optical properties of the sensor," he explains. "We can then observe the effects on these properties through changes in the transmitted laser light."

This device has a number of potential applications in the areas of food safety, medical testing and environmental monitoring.

Rapid-detection devices that will help the food industry detect low levels of several different organism will help Georgia's food processing industry by saving local plants time and money, says Edmonds.

"As of today, there are few microbiological-based tests," he explains. "Right now the producers must run conventional laboratory tests, which are so slow it takes three to four days to get the results back. That's a lot of waiting time for the products."

And, currently available systems to test for pathogens can cost from $50,000 to $250,000. The rapid-response biosensor's projected cost is in the range of a few hundred dollars to less than $5,000. Cost per test -- the real issue -- is likely to be in the tens of cents range.

"The apparatus we're developing at Georgia Tech will be recyclable and is very inexpensive," Edmonds says. "The producers at the food processing plant can potentially test the product on-line without having to incur the expense and time of laboratory analyses. With fast information, the producers could then respond in a more aggressive manner to any sources of potential contamination. And if they get a quick turnaround time in just a few hours and have confidence that the product is safe, they can move the product more rapidly into the marketplace."

Hartman and Edmonds expect that a prototype rapid-response biosensor will be available for field testing in processing plants by the end of 1996.
-- Dara O'Neil

Further information is available from:

Dr. Paul Edmonds, School of Biology, Georgia Institute of Technology, Atlanta, GA 30332-0230. (Telephone: 404/894-3737) (E-mail: paul.edmonds@biology.gatech.edu)

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Last updated: 12 Sept. 1996