Location: Meat Safety & Quality ResearchTitle: Proper context: Comparison studies demonstrate that United States food-animal production antimicrobial uses have minimal impact on antimicrobial resistance
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2017
Publication Date: 8/13/2017
Citation: Schmidt, J.W., Wheeler, T.L., Arthur, T.M. 2017. Proper context: Comparison studies demonstrate that United States food-animal production antimicrobial uses have minimal impact on antimicrobial resistance. Meeting Abstract. [Abstract]. International Sysmposium on the Environmental Dimension of Antibiotic Resistance (4th), Lansing, Michigan, August 13-17, 2017. http://www.antibiotic-resistance.de/.
Technical Abstract: In the United States (US) it is estimated that food-animal production agriculture accounts for >70% of antimicrobial (AM) use leading to concerns that agricultural uses "substantially drive" antimicrobial resistance (AMR). Many studies report AMR in food-animal production settings without comparison to other environments. This practice leads to a false pretense that the AMR observed was due solely to the type and amount of AM used in the food-animal production setting. To determine, in the proper context, the impact of AM uses in US cattle and swine production we performed a series of studies that incorporated culture-dependent and culture-independent methods. These studies included: (i) a comparison of the AMR present in feces of beef cattle produced with and without antibiotics, (ii) a comparison of the AMR present in ground beef and pork chops from animals produced with and without antibiotics, (iii) determinations of the AMR impacts resulting from two of the AMs most frequently administered in-feed to US beef cattle (chlortetracycline and tylosin), and (iv) compared the AMR associated with beef cattle production waste, swine production waste, human municipal waste water treatment plant effluent, and environments not impacted by wastes. Generally, antimicrobial use during food-animal production had either small or no observed impact on AMR occurrence. Interestingly, the prevalences and concentrations of AMR bacteria populations were similar among the food-animal and municipal sample sources, but the numbers of multiple classes of AMR were significantly higher (P < 0.05) in municipal samples than in food-animal samples. Additionally multidrug resistant isolates were found in environments with little to no impact by human or food-animal waste. These results led us to a hypothesis that background levels of AM-resistant bacteria in soil expand when nutrients are added including the nutrients provided by manure. We additionally report the results of an experiment that demonstrated that the addition of nutrients to soil drives AMR increases. We conclude AMR is ubiquitous, with resistant bacterial sub-populations present in most if not all environments, and nutrient enrichment likely plays a larger role than AM use in AMR occurrence.