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Cattle.
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When fed in low doses, sodium
chlorate kills Salmonella typhimurium and Escherichia coli
O157:H7 in pigs and cows. Agricultural
Research Service scientists in College Station, Texas, have shown that
levels of these harmful bacteria can be reduced in the intestinal tract of pigs
and cows if they're given sodium chlorate before slaughter.
"Because the gut and lymph tissue of meat animals and chickens are major
reservoirs for Salmonella and E. coli O157:H7, this research
offers a practical approach for reducing on-farm concentrations of these
pathogens," says David J. Nisbet, an ARS microbiologist and research
leader for the Food and Feed Safety Research Unit in College Station. Fewer
bacterial pathogens in the gut can significantly reduce the chance of carcass
contamination during food processing.
These two bacteria—culprits in most cases of human food poisoning—can
live both aerobically and anaerobically, that is, with or without air. That
makes them different from most gut bacteria, which are anaerobes.
Salmonella and E. coli O157:H7 contain an enzyme known as a
respiratory nitrate reductase. This enzyme coincidentally converts the chlorate
to chlorite, which kills the harmful bacteria. Beneficial bacteria in the
intestinal tract lack respiratory nitrate reductase, so they are not affected
by the addition of chlorate. The cost of using sodium chlorate at a meat
processing facility could be less than 10 cents per pig, estimates ARS
microbiologist Robin C. Anderson.
In laboratory studies, 45 weaned pigs were fed up to 0.04 grams of sodium
chlorate per kilogram of body weight after being infected with S.
typhimurium. Within 16 hours, the treatment produced a 150-fold reduction
in the number of pathogenic cells in the intestines.
"The research is in the early stages," cautions Anderson. Before this
approach could be widely used in the United States, the Food and Drug
Administration would need to approve its use.
"But if results from large field trials hold up, I can envision a
marketing system that includes feeding chlorate to animals before they're
transported to slaughter. Another opportunity would be to add chlorate to
drinking water at the slaughterhouse," Anderson adds.
The Centers for Disease Control and Prevention estimate that about 1.4 million
cases of salmonellosis and 73,000 cases of diarrheal illness due to E.
coli O157:H7 occur in the United States each year.
Anderson, Nisbet, and ARS microbiologist Larry H. Stanker have applied for a
patent. Results of the study conducted with weaned piglets were published in
the February 2001 issue of The Journal of Food Protection.—By
Linda
McGraw, Agricultural Research Service Information Staff.
This research is part of Food Safety (Animal and Plant Products), an ARS
National Program (#108) described on the World Wide Web at
http://www.nps.ars.usda.gov.
Robin C. Anderson and
David J. Nisbet are in the USDA-ARS
Food & Feed Safety Research Unit,
Southern Plains Agricultural Research Center, 2881 F&B Road, College
Station, TX 77845; phone (979) 260-9484 [Nisbet], (979) 260-9317 [Anderson],
fax (979) 260-9332. |
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