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<oL> <LI> Determine the effect of exposure to antibiotics, food preservatives, and sanitizers on emergence of mar mutants of E. coli 0157:H7 and S. enteritidis and the cross-resistance of mar mutants to non- inducing chemical agents. <LI>Determine prevalence of mar mutants of Enterobacteriaceae of environmental origin. <LI>Determine induction of mar in complex matrices (animal feeds, manure, and food). <LI>Compare growth and survival of mar mutants to the wildtype strains (traditional growth media, and food and environmental samples).
E. coli 0157:H7 and Salmonella isolated from human, animal and environmental sources will be screened following exposure to a selected antimicrobial agent for cross-resistance to other unrelated antimicrobial agents. Target bacteria will be exposed to manure and food matrices to determine whether such conditions can induce mar or select for mar mutants. Growth and survival of wildtype and mutants will be compared in nutrient media and food matrices to determine whether mutants have a survival advantage. Enterobacteriaceae isolated from environmental samples will be screened for mar mutation using RT-PCR.
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Antibiotic resistance of foodborne pathogens, E. coli 0157:H7 and S. enteritidis, is a global concern with respect to public health and safety. We hypothesize exposure of foodborne pathogens to antibiotics on the farm results in induction of the mar locus conferring resistance to the inducing agent and other unrelated antimicrobial compounds and that sanitizers and preservatives used by the food industry results in induction of mar conferring resistance to other sanitizers and preservatives and antibiotics used to treat human disease.
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The goal of this project is to provide a better understanding of mechanisms associated with bacterial antimicrobial resistance by investigating the role of the regulatory mar (multiple antibiotic resistance) locus in conferring resistance to antibiotics, sanitizers, and preservatives. Expression of mar activates efflux pumps, changes membrane composition, and increases production of cytoprotective proteins. The project is relatively new (6 months since start) and real progress only now starting to occur. We have started to screen isolates, have developed a northern blot procedure, are sequencing the mar operon of mutants to determine location of mutation within the operon.
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The research outlined in the present proposal, is designed to advance fundamental knowledge on a mechanism of antimicrobial resistance that key foodborne pathogens possess. This information will allow us to identify experimentally specific conditions that result in resistance to antibiotics and other chemically unrelated compounds, ultimately resulting in development of strategies to control foodborne pathogens. We emphasize that wholesale stoppage of chemical sanitizers and preservatives by the food industry is not at stake, but perhaps rather a reconsideration of current GAP's, GMP's, SSOP's and HACCP systems. Similarly, banning the use of antibiotics in animal agriculture is not an issue, but rather the prudent use of antibiotics is underscored.