Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 19, 2001
Publication Date: May 22, 2002
Interpretive Summary: E. coli is a food borne bacteria that lives in the gut of cattle. E. coli strain O157:H7 is associated with ground beef and sickens over 76,000 Americans each year. Sodium chlorate kills E. coli. Cattle experimentally infected with E. coli O157:H7 were treated with sodium chlorate in drinking water. Chlorate reduced total E. coli, and E. coli O157:H7 populations throughout the gut. This study indicated that treatment with sodium chlorate could be a means to reduce food-borne illnesses by reducing disease causing bacteria in cattle prior to slaughter.
Technical Abstract: Cattle are a natural reservoir of the food-borne pathogen Escherichia coli O157:H7. Therefore, strategies that reduce E. coli O157:H7 prior to slaughter will reduce human exposures to this virulent pathogen. Bacteria that can anaerobically respire on nitrate (e.g., E. coli) are killed by exposure to chlorate because the intracellular enzyme nitrate reductase, which converts nitrate to nitrite, also co-metabolically reduces chlorate to cytotoxic chlorite. Because chlorate is bactericidal only against nitrate reductase-positive bacteria, it has been suggested that chlorate supplementation be used as a strategy to reduce E. coli O157:H7 populations in cattle prior to harvest. Cattle (n=8) were fed a feedlot- style high grain ration and experimentally infected with 3 strains of E. coli O157:H7. Cattle were given access to drinking water supplemented with 2.5 mM KNO3 and 100 mM NaCl (Controls; n=4) or 2.5 mM KNO3 and 100 mM NaClO3 (Chlorate-treated; n=4). Sodium chlorate treatment for 24 h reduced the population of all E. coli O157:H7 strains approximately 2 logs (10**4 to 10**2) in the rumen and 3 logs (10**6 to 10**3) in the feces. Chlorate treatment reduced total coliforms and generic E. coli from 10**6 to 10**4 in the rumen and by 2 logs throughout the rest of the gastrointestinal tract (ileum, cecum, colon and rectum). Chlorate treatment reduced E. coli O157:H7 counts throughout the intestinal tract, but did not alter total culturable anaerobic bacterial counts or the ruminal fermentation pattern. Therefore, it appears that chlorate supplementation is a viable potential strategy to reduce E. coli O157:H7 populations in cattle prior to harvest.