Food Technology: Pathogen testing speeds up

Judy Keller

KING OF PRUSSIA, PA—Finding foodborne pathogens before they contaminate a finished product is every food manufacturer's goal. Increased microbiological testing and more reporting of food recalls has heightened consumer awareness and has driven the food industry to protect their brand names through better, faster testing.

With that growing need in mind, biotechnology firm Molecular Circuitry Inc. (King of Prussia, PA) and VWR Scientific Products (Westchester, PA), a distributor of cleanroom products, recently teamed to launch Detex, a new technology designed to help the food industry find harmful bacteria faster.

The Detex pathogen detection system tests for contaminants in meat, poultry and other perishable foods.
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The Detex pathogen detection system is a self-contained, automated testing instrument that uses combinations of antibodies and a new proprietary growth medium to test for contaminants in meat, poultry or other perishable foods—an improvement, the companies say, from the conventional dipstick-style indicator tests.

The “capture antibody” is used to coat the cartridge surface. This pulls out pathogenic bacteria from the mixtures present in incubated food samples. The unbound material is washed off, and the bound bacteria are reacted with a second antibody. By using a second gold-conjugated antibody of different specificity, the Detex system subtypes pathogenic strains and provides identification of samples.

The system comprises an MC-18 instrument, disposable pathogen-specific test cartridges and disposable reagent packs. Each MC-18 instrument has a carousel capable of accepting 27 cartridges and 9 reagent packs.

The packs contain all the reagents and buffers needed for the tests and have a shelf life of about six months with refrigeration. The cartridges are injection-molded plastic, with six electrical resistors attached that are designed to work with a sample volume of 150 Joules.

According to Dennis Bird, VWR Scientific's marketing manager, within the same test cartridge several tests can be used to detect the same pathogen or testing for several pathogens at once can be done. Each cartridge can perform six tests.

The device is barcode compatible and can be used with LIMS computerized systems.

“Our target audience for this product is anyone in the food and beverage industry who needs to test for pathogens quickly,” Bird says.

Detex gives test results in three hours for E. coli 0157 (including H7 strain). Current conventional tests give results in six to 24 hours.

At this point, the Detex system has met with some favorable results.

According to Evelyn Haley, lab supervisor at Solcroft, PA-based Keystone Foods, Keystone has tested the Detex in side-by-side comparisons with conventional tests for E. coli 0157:H7 and Campylobacter. Haley says the new technology performed well overall and proved to be easy to use.

While she refuses to release specific numbers for false-alarm rates and accuracy, Haley says that when Detex results conflicted with the side-by-side conventional tests, a subculture was done and the results came out negative for pathogens every time. She says Keystone has used the system for about a year, along with conventional approved methods.

“Basically, you put in a core sample and walk away for three hours and return to find results. It doesn't tie up personnel, and just about anyone can use it,” Haley says. “The results are clear cut, black-and-white.”

On April 6, the AOAC Research Institute (formerly the Association of Official Analytical Chemists) granted Performance Tested Methods status to the Detex system.

A spokesman for the Institute says testing under the direction of the AOAC verified performance claims of 98 percent sensitivity, 90 percent specificity and 96 percent accuracy. The overall method agreement between Detex and the U.S. Department of Agriculture Food Safety and Inspection Service (FSIS) method was 96 percent.

These data suggest that the Detex method is comparable to the SDA/FSIS method of detection of E. coli 0157 in raw ground beef and raw ground poultry.

Wallace Andrews of the Division of Microbiological Studies FDA, Washington; Ann Draughon, of the University of Tennessee, Food Science and Technology, Knoxville, TN; and Richard Wilson, formerly of Penn State University, University Park, PA, served as expert reviewers for the Detex system. The Silliker Laboratories Corporate Research Laboratory in Chicago participated as the independent laboratory.


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