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Reducing Salmonella and E. coli 0157:H7 at the Farm

By Linda McGraw
March 5, 2001

A practical approach to reducing two key on-farm pathogens in pigs and cows has been developed by Agricultural Research Service researchers in College Station, Texas. The scientists report that sodium chlorate, fed in low doses to pigs and cows before slaughter, selectively kills the pathogens Salmonella typhimurium and E. coli 0157:H7.

The scientists in the ARS Food and Feed Safety Research Unit in College Station developed an animal model showing that sodium chlorate reduces these harmful bacteria in the animal intestinal tract. Gut and lymph tissue in meat animals and chickens are major reservoirs for salmonella and E. coli 0157:H7. The U.S. Centers for Disease Control and Prevention estimate that about 1.4 million cases of salmonellosis and 73,000 cases of diarrheal illness caused by 0157:H7 occur in the U.S. each year.

Salmonella and E. coli 0157:H7 have an enzyme--respiratory nitrate reductase--that beneficial intestinal bacteria lack. This enzyme converts the sodium chlorate to chlorite, which kills the harmful bacteria. Because the beneficial bacteria lack respiratory nitrate reductase, they are unharmed by the added chlorate.

In laboratory studies, 45 weaned pigs were fed as much as 0.04 grams of sodium chlorate per kilogram of body weight after being inoculated with S. typhimurium. Within 16 hours, the treatment produced a 150-fold reduction in the number of pathogenic cells in the intestines.

The U.S. Department of Agriculture applied for a patent on behalf of the inventors, ARS microbiologists Robin C. Anderson and David J. Nisbet in College Station and Larry H. Stanker in Albany, Calif. The researchers are seeking a cooperative research partner to further develop the work for commercial meat processing. Besides adding the chlorate to feed, the researchers suggest that a more realistic approach would be to add the chlorate to drinking water for the animals upon arrival at the processing facility. However, the Food and Drug Administration would need to approve any wide-scale use of the technique in food processing facilities.

For more details, see the March issue ofAgricultural Research.

ARS is the chief scientific research agency of USDA.

Scientific contacts: David J. Nisbet, ARS Food & Feed Safety Research, College Station, Texas, phone (979) 260-9368, fax (979) 260-9332, or Robin C. Anderson (979) 260- 9317,