Antibiotic Resistance Patterns of Major Zoonotic Pathogens from All-Natural, Antibiotic-Free, Pasture-Raised Broiler Flocks in the Southeastern United States

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 (, , , and ) 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 and and least prevalent in . Although and were isolated from the same farms and characterized using the same NARMS plates, they exhibited distinct AR profiles, with demonstrating clear farm-specific resistance patterns. Multidrug resistance rates (three or more antibiotics), in order of prevalence, were (63.9%), (36.0%), (12.7%), and (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.

Antibiotic discovery throughout the Small World Initiative: A molecular strategy to identify biosynthetic gene clusters involved in antagonistic activity

“…Moreover, resistance is not confined to nosocomial settings. Environmental strains also encode resistance (Leamer, Clemmons, Jordan, & Pacha, ; Rose et al., ; Rothrock, Hiett, Guard, & Jackson, ) and contribute to life‐threatening community‐acquired infections (Furuya‐Kanamori et al., ; Leamer et al., ; McKenna, ; Schinasi et al., ). Escalating the crisis is the shift of major pharmaceutical companies away from antibiotic discovery and synthesis due to low profitability (Pammolli, Magazzini, & Riccaboni, ; Scannell, Blanckley, Boldon, & Warrington, ).…”

“…Moreover, resistance is not confined to nosocomial settings. Environmental strains also encode resistance (Leamer, Clemmons, Jordan, & Pacha, 2013;Rose et al, 2009;Rothrock, Hiett, Guard, & Jackson, 2016) and contribute to lifethreatening community-acquired infections (Furuya-Kanamori et al, 2015;Leamer et al, 2013;McKenna, 2008;Schinasi et al, 2014).…”

Listeria Occurrence and Potential Control Strategies in Alternative and Conventional Poultry Processing and Retail

“…contamination of MPPUs or other alternative processing facilities. However, Rothrock et al (2016b) did investigate multi drug resistance (MDR) isolates in pasture flocks and found comparable rates of MDR Listeria spp. in flock processed by a USDA inspected facility and on-farm processing.…”

Application of genomic technologies to measure and monitor antibiotic resistance in animals

“…Conventional culture‐based techniques are classical methods to identify antibiotic resistance in the environment. Although culture‐independent approaches have been used, the determination of break point values and resistance patterns is more frequently based on culture‐dependent methods . The use of culture media with selective antibiotics allows the enumeration and isolation of specific bacterial groups.…”

“…In general, culture‐dependent methods are laborious and time consuming, and their major limitation stems from the small fraction of bacteria that can be cultivated from a complex environment . Nevertheless, pathogens and indicator bacteria are easily grown on selective media using standard procedures, which facilitate the profiling of both resistance phenotypes and genotypes of bacteria and further assessment of their potential risks to human health …”