Location: Meat Safety & Quality ResearchTitle: Impact of raised without antibiotics practices on occurrences of antimicrobial resistance Author
|Rovira, Pablo - Colorado State University|
Submitted to: American Society for Microbiology General Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 1/27/2017
Publication Date: 3/22/2017
Citation: Vikram, A., Rovira, P., Miller, E.W., Agga, G.E., Wheeler, T.L., Arthur, T.M., Schmidt, J.W. 2017. Impact of raised without antibiotics practices on occurrences of antimicrobial resistance. [Abstract]. American Society for Microbiology General Meeting. p. 14, S1:5.
Technical Abstract: Background: The increasing occurrence of antimicrobial-resistant human infections has been attributed to the use of antimicrobials in a variety of applications including food-animal production. "Raised without antibiotics" (RWA) meat production has been offered as a practice to reduce antimicrobial-resistant (AR) human infections. The goal of this research was define the impact of RWA practices by comparing the levels of antimicrobial resistance (AMR) in feces of cattle RWA and produced using antimicrobials, termed "conventional" (CONV). We also compared the levels of AMR in ground beef and pork chops from RWA and CONV production systems. Methods: Over 12 months cattle fecal samples (N = 719) were recovered from 36 CONV lots and 36 RWA lots. CONV ground beef (N = 191), RWA ground beef (N = 179), CONV pork chop (N = 190), and RWA pork chop (N = 182) samples were collected from three different suppliers over 13 months. Individual fecal and meat samples were cultured to determine the prevalences and concentrations of AR Enterococcus, Escherichia coli, and Salmonella. AR Staphylococcus aureus was also cultured from meat samples. For fecal samples, genomic DNA was pooled by lot, sequenced with an Illumina Nextseq to a mean depth of 90 million reads, and queried against Colorado State University database of antimicrobial resistance genes (ARGs), MEGARes. Results: AR E. coli were slightly higher in CONV feces, but occurrences were affected more significantly by factors other than antimicrobial use (season, total E. coli concentration). Erythromycin-resistant (ERYr) Enterococcus concentrations were 1.18 log10 CFU/g higher in CONV feces. Tetracycline-resistant E. coli and S. aureus were slightly higher in CONV ground beef, but supplier and season significantly affected their prevalences. ERYr S. aureus was slightly higher in RWA pork chops, but supplier and season significantly affected prevalence. Metagenomic sequencing detected 43 ARGs in feces and all lots harbored ARGs from aminoglycoside, beta-lactam, macrolide-lincosamide-streptogramin (MLS), and tetracycline classes. Overall, slightly more ARGs were in CONV feces (24.4 ARGs/sample) than in RWA feces (21.7 ARGs/sample). Conclusions: Restrictions on antimicrobial use during beef production in the US may not reduce the occurrence of antimicrobial-resistant human infections since the magnitude of AMR reductions in RWA feces and meat products were small relative to the overall occurrences of AMR.