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Scientists Develop Method To Detect Live E. Coli In Beef

08 September 2009

Missouri

US - University of Missouri food scientists have come up with a new method to detect live Escherichia coli cells in ground beef.

Up to 70,000 people in the US become ill each year from infection with E. coli O157:H7. This bacterium colonises the intestinal tract of cattle and can contaminate beef products during slaughter and processing.

Researchers at the University of Missouri have developed a two-step method that can distinguish between dead and living E. coli cells. Dead cells will not make people sick, but as few as ten live cells can inflict sever intestinal illness, said Ms Mustapha, the associate professor of food science in the MU College of Agriculture, Food and Natural Resources.

The research employs a technique called a real-time polymerase chain reaction (PCR). This is a quick, reliable method for detecting and identifying pathogens in food. PCR, however, can't differentiate viable from dead microbial cells. The presence of dead pathogenic cells may result in false-positive findings, which could lead to unnecessary product recalls, Ms Mustapha said.

To prevent this, researchers stain samples with a dye called ethidium bromide monoazide (EMA). EMA can't penetrate live cells, but it can enter dead cells, where it binds to DNA molecules, making them insoluble and therefore invisible to PCR tests.

The researchers have successfully tested the technique on ground beef, chicken and eggs. Testing takes about 12 hours, as opposed to older methods, which require up to two days for results.



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