Abstract
Antimicrobial resistant determinants (ARDs) can be transmitted from livestock systems through meat products or environmental effluents. The public health risk posed by these two routes is not well understood, particularly in non-pathogenic bacteria. We collected pooled samples from 8 groups of 1741 commercial cattle as they moved through the process of beef production from feedlot entry through slaughter. We recorded antimicrobial drug exposures and interrogated the resistome at points in production when management procedures could potentially influence ARD abundance and/or transmission. Over 300 unique ARDs were identified. Resistome diversity decreased while cattle were in the feedlot, indicating selective pressure. ARDs were not identified in beef products, suggesting that slaughter interventions may reduce the risk of transmission of ARDs to beef consumers. This report highlights the utility and limitations of metagenomics for assessing public health risks regarding antimicrobial resistance, and demonstrates that environmental pathways may represent a greater risk than the food supply.
Highlights
Food production and food products are important potential sources of antimicrobial resistant (AMR) infections in humans
This study reports the use of shotgun metagenomics in a novel investigation of AMR that tracked specific pens of intensively-managed cattle from feedlot entry through slaughter to market-ready product in a longitudinal fashion
While our results are more directly relevant to large North American feedlot operations, the general approach can be extended to other sectors of beef production, other countries, and other livestock production systems
Summary
Food production and food products are important potential sources of antimicrobial resistant (AMR) infections in humans. In North American beef production, several critically important antimicrobial drugs (AMDs) such as fluoroquinolones, macrolides and thirdgeneration cephalosporins are used, while others are not, e.g., carbapenems (World Health Organization, 2011; Food and Drug Administration, 2003). Use of these AMDs is thought to increase the risk of AMR being transmitted to humans through environmental exposures (i.e., air, water and soil), occupational exposures (Levy et al, 1976; Moon et al, 2015), as well as through consumption of beef products (Antibiotic Resistance from the Farm to the Table [Internet], 2014).
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