Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 16, 2004
Publication Date: March 15, 2004
Citation: Callaway, T.R., Anderson, R.C., Edrington, T.S., Bischoff, K.M., Genovese, K.J., Poole, T.L., Byrd II, J.A., Harvey, R.B., Nisbet, D.J. 2004. Effects of sodium chlorate on antibiotic resistance in Escherichia coli O157:H7. Foodborne Pathogens and Disease. 1:59-63. Interpretive Summary: Sodium chlorate has been proposed for use as a method to reduce food borne pathogenic bacteria in food animals. Chlorate kills Escherichia coli O157:H7 in the gut of food animals prior to slaughter. However, the effect of chlorate on antibiotic resistance of bacteria has not been previously examined. The antibiotic resistance profiles of chlorate-resistant E. coli O157:H7 strains were found to not be significantly different from parent strains. It appears that chlorate treatment will not lead to a widespread dissemination of antibiotic resistance.
Technical Abstract: The elimination of food borne pathogens from animals prior to slaughter could greatly reduce the number of human food borne illnesses. The spread of antibiotic resistance from farm animals to human pathogens has become a matter of great public health significance, and methods to reduce food borne pathogenic bacteria without utilizing traditional antibiotics have been sought. Chlorate kills Escherichia coli O157:H7 in vitro and in vivo and has been proposed as a feed additive to be included in food animal rations immediately prior to slaughter to reduce E. coli O157:H7 populations in the animal gastrointestinal tract. However, the effects of chlorate on the antibiotic resistance of targeted bacterial species have not been previously examined. In pure culture, it is quite easy to produce chlorate-resistant mutants, but these mutants do not compete well in mixed culture conditions. Therefore this study was designed to examine any effect that the development of chlorate resistance in E. coli O157:H7 has on resistance to medically important antibiotics. Chlorate-resistant mutants were quickly created from two strains of E. coli O157:H7. Chlorate numerically increased antibiotic resistance in both E. coli O157:H7 strains for only a single antibiotic (sulfadimethoxine); but the resistance to several antibiotics increased slightly within an individual strain. Based on these results it appears unlikely that chlorate treatment will result in a widespread dissemination of antibiotic resistance, however further research is needed to confirm these results.