Antibiotic Resistance Patterns of Major Zoonotic Pathogens from All‐Natural, Antibiotic‐Free, Pasture‐Raised Broiler Flocks in the Southeastern United States. Issue 2 (1st March 2016)

• Record Type: Journal Article
• Authors: Rothrock, Michael J.; Hiett, Kelli L.; Guard, Jean Y.; Jackson, Charlene R.
• Is Part Of: Journal of Environmental Quality. Volume 45:Issue 2(2016)
• Page Start: 593
• Page End: 603
• Publication Date: 2016-03-01
• Subjects: Agricultural ecology -- Periodicals; Environmental engineering -- Periodicals; Pollution -- Periodicals; 630
• DOI: 10.2134/jeq2015.07.0366
• Languages: English
• ISSNs: 0047-2425

Abstract

Abstract : The use of antibiotics in agroecosystems has been implicated in the rise in antibiotic resistance (AR), which can affect environmental, animal, and human health. To determine the environmental impact of antibiotic use in agroecosystems, appropriate background levels of AR in agricultural environments in the absence of antibiotic application must be determined. Therefore, to determine background levels of AR in broiler production, four target microbes ( Escherichia coli, Salmonella, Campylobacter, and Listeria ) were isolated from 15 all‐natural, antibiotic‐free, pasture‐raised broiler flocks from six farms within the southeastern United States. The AR 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 and farms and throughout the life cycle of the flocks along the farm‐to‐fork continuum. Antibiotic resistances were most prevalent in Listeria and Salmonella and least prevalent in Campylobacter . Although E. coli and Salmonella were isolated from the same farms and characterized using the same NARMS plates, they exhibited distinct AR profiles, with Salmonella demonstrating clear farm‐specific resistance patterns. Multidrug resistance rates (three or more antibiotics), in order of prevalence, were Listeria (63.9%), Salmonella (36.0%), E. coli (12.7%), and Campylobacter (1.4%). The results of this study demonstrate the variability in background AR 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 account for this highly dynamic background AR. Core Ideas: Determining background levels of AR in antibiotic‐free agroecosystems is essential. AR within antibiotic‐free broiler production is dynamic among the zoonotic pathogens. Multidrug resistance was greater in Salmonella and Listeria . Multidrug resistance was farm specific for Salmonella and Campylobacter . E. coli was not an appropriate indicator of AR in other Gram‐negative organisms, including Salmonella.