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Detect live E. coli cells in beef.

According to the National Centers for Disease Control and Prevention, about 70,000 people in the United States become ill each year from infection with E. coli O157:H7. This bacterium colonizes the intestinal tract of cattle and can contaminate beef products during slaughter and processing.

E. coli can be transmitted to meat during food processing and also by unsanitary home preparation methods. The bacteria can survive both refrigeration and freezer storage. Most confirmed cases of E. coli infection have been associated with undercooked ground beef. In 2% to 15% of the cases in children, the infection may develop into hemolytic uremic syndrome. This condition can ultimately lead to kidney failure with the possible permanent loss of kidney function and even death.

Now, University of Missouri food scientists have come up with a dye-based method to detect live E. coli cells in ground beef. The researchers developed a two-step technique that can distinguish between dead and living E. coli cells. Dead cells won't make you sick, but as few as 10 live cells can inflict a severe intestinal illness.

We're told that this is the first such research using these methods in testing beef. The scientists have reported on the research, funded by the National Cattlemen's Association, in the Journal of Applied Microbiology. The research employs the 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.

To prevent this, the university researchers stain samples with an ethidium bromide monoazide dye. The dye 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 scientists 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. The researchers plan to continue the research by trying to improve the technology's sensitivity and by applying it to other types of foods or surfaces.

Further information. Azlin Mustapha, Department of Food Science, University of Missouri, 256 WC Stringer Wing, 221 Eckles Hall, Columbia, MO 65211; phone: 573-882-2649; fax: 573-884-7964; email: mustaphaa@missouri.edu.
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Publication:Microbial Update International
Date:Dec 1, 2009
Words:388
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