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New Test Developed for Detecting E. coli

Last week, scientists at the National Meeting of the American Chemical Society reported on the development of the first two-in-one test for detecting E. coli bacteria and the toxins or poisons that the bacteria use to cause symptoms in victims.

E. coli O157 bacteria may be found in food for hours or days before improper storage conditions allow them to grow and produce toxins that cause food poisoning.  Toxins can remain in food even after the bacteria die.

lab-ecoli-test-featured.jpgIn the past, it took two different tests, one for bacteria and the other for toxins in order to ensure that meat was safe for sale.

“Our test may be used in meat processing plants to allow in-house testing of products prior to sale,” project leader at the U.S. Department of Agriculture (USDA), John Mark Carter told Science Daily.  “This would reduce the frequency of foodborne illness, reduce product recalls, and enhance public health while reducing annual cost for food testing,” he said.  Carter works in Albany, CA  for the USDA’s Agricultural Research Service.

More than 70,000 people are stricken with food poisoning each year caused by E. coli O157, and the bacterium is blamed for at least 60 deaths.  Ground beef is at the top of the list of concerns over food safety, though E. coli outbreaks have been reported in foods like lettuce, spinach, raw milk, and cookie dough.

E. coli may get into ground beef when meat is contaminated with fecal material from cattle during slaughter or processing.  When meat is not properly chilled, bacteria can multiply and produce two primary toxins, Shiga toxin 1 and 2, which create illness in humans.

Until recently, separate tests were required for each bacterial threat.  Both tests were time-consuming as results take an average of three to five days.  The new two-in-one test cuts waiting time to just 24 hours, researchers said.  Though the new test is slightly less sensitive, scientists think that the sensitivity can be improved.

The 2-in-1 test uses microscopic plastic beads, each one-one hundredth the with of a grain of sand, that contain a fluorescent dye.  Carter’s USDA lab customized the beads by coating them with antibodies that lock onto proteins or antigens present on E. coli and the two main toxins.  During the testing process, “the beads are mixed together with ground beef or other food samples and then separated and run through an instrument.  It identifies beads that have latched onto the E. coli antigens,” Science Daily wrote.

“Finding a few E. coli bacteria in a large sample of ground beef or other food is like looking for a needle in a haystack,” Carter said.  “This new method makes the needle much easier to find, compared to standard methods.  But improvements in sampling and sensitivity are still needed.”

The test can be used on meats as well as fruits, vegetables, and other foods and beverages. Looking ahead, scientists hope to create beads that can detect other foodborne microbes, such as Salmonella and Listeria.  USDA scientists are working in tandem with the Luminex Corporation in hopes to commercialize the E. coli test in order to have it quickly adapted by government agencies involved in food inspection, as well as meat producers. 

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