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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Egg and Poultry Production Safety Research Unit » Research » Publications at this Location » Publication #319004
Title: Antibiotic resistance patterns of major zoonotic pathogens from all-natural, antibiotic-free, pasture-raised broiler flocks in the southeastern United States

Author
item Rothrock, Michael
item Hiett, Kelli
item Guard, Jean
item Jackson, Charlene

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2015
Publication Date: 3/1/2016
Citation: Rothrock Jr, M.J., Hiett, K.L., Guard, J.Y., Jackson, C.R. 2016. Antibiotic resistance patterns of major zoonotic pathogens from all-natural, antibiotic-free, pasture-raised broiler flocks in the southeastern United States. Journal of Environmental Quality. 45(2):593-603.

Interpretive Summary: The use of antibiotics in agroecosystems has been implicated in the rise in antibiotic resistance that can affect environmental, animal, and human health. In order to effectively determine the environmental impact of antibiotic use in agroecosystems, appropriate background levels of antibiotic resistance in agricultural environments in the absence of antibiotic application needs to be determined. Therefore, to determine background levels of antibiotic resistance in broiler production, 4 target microbes (Escherichia coli, Salmonella spp., Campylobacter spp., Listeria spp.) were isolated from 15 all-natural, antibiotic-free, pasture-raised broiler flocks from 6 farms within the Southeastern United States. These antibiotic resistance profiles of these isolates were characterized using the CDC National Antimicrobial Resistance Monitoring System for Enteric Bacteria (NARMS), and these resistance patterns were compared across target microbes, across farms, and throughout the life cycle of the flocks along the farm-to-fork continuum. Antibiotic resistances were most prevalent in Listeria spp. and Salmonella spp., and the least prevalent in Campylobacter spp. Even though isolated from the same farms and characterized using the same NARMS plates, E. coli and Salmonella spp. exhibited distinct antibiotic resistance profiles, with Salmonella spp. demonstrating a clear resistance pattern based on farm of origin. Multi-drug resistance (3+ antibiotics), in order of prevalence, was Listeria spp. (63.9%), Salmonella spp. (36.0%), E. coli (12.7%), Campylobacter spp. (1.4%). The results of this study demonstrate the variability in background antibiotic resistances among major food safety-related microbes, even when isolated from similar production and processing samples from the same farms, and indicate the need for the proper design of future broiler production studies to effectively account for this highly dynamic background antibiotic resistance.

Technical Abstract: The use of antibiotics in agroecosystems has been implicated in the rise in antibiotic resistance that can affect environmental, animal, and human health. In order to effectively determine the environmental impact of antibiotic use in agroecosystems, appropriate background levels of antibiotic resistance in agricultural environments in the absence of antibiotic application needs to be determined. Therefore, to determine background levels of antibiotic resistance in broiler production, 4 target microbes (Escherichia coli, Salmonella spp., Campylobacter spp., Listeria spp.) were isolated from 15 all-natural, antibiotic-free, pasture-raised broiler flocks from 6 farms within the Southeastern United States. These antibiotic resistance profiles of these isolates were characterized using the CDC National Antimicrobial Resistance Monitoring System for Enteric Bacteria (NARMS), and these resistance patterns were compared across target microbes, across farms, and throughout the life cycle of the flocks along the farm-to-fork continuum. Antibiotic resistances were most prevalent in Listeria spp. and Salmonella spp., and the least prevalent in Campylobacter spp. Even though isolated from the same farms and characterized using the same NARMS plates, E. coli and Salmonella spp. exhibited distinct antibiotic resistance profiles, with Salmonella spp. demonstrating a clear resistance pattern based on farm of origin. Multi-drug resistance (3+ antibiotics), in order of prevalence, was Listeria spp. (63.9%), Salmonella spp. (36.0%), E. coli (12.7%), Campylobacter spp. (1.4%). The results of this study demonstrate the variability in background antibiotic resistances among major food safety-related microbes, even when isolated from similar production and processing samples from the same farms, and indicate the need for the proper design of future broiler production studies to effectively account for this highly dynamic background antibiotic resistance.