Location: Meat Safety & Quality ResearchTitle: Impact of antimicrobial use during beef production on fecal occurrence of antimicrobial resistance Author
|Rovira, Pablo - Colorado State University|
|Bosilevac, Joseph - Mick|
|Morley, Paul - Colorado State University|
|Belk, Keith - Colorado State University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/17/2017
Publication Date: 2/28/2017
Citation: Vikram, A., Rovira, P., Agga, G.E., Arthur, T.M., Bosilevac, J.M., Wheeler, T.L., Morley, P., Belk, K., Schmidt, J.W. 2017. Impact of antimicrobial use during beef production on fecal occurrence of antimicrobial resistance. Meeting Abstract. [Abstract]. Beef Industry Safety Summit, February 28-March 2, 2017, Houston, Texas. Available:http://bifsco.org/search.aspx?qal=2017 abstracts.
Technical Abstract: Objective: To determine the impact of typical antimicrobial use during cattle production on fecal occurrence of antimicrobial resistance by culture, quantitative PCR, and metagenomic sequencing. Experimental Design & Analysis: Feces were recovered from colons of 36 lots of "conventional" (CONV) cattle and 36 lots of "raised without antibiotics" (RWA) cattle at a commercial beef processing plant during monthly visits from February 2014 to January 2015. For each lot, 10 individual samples were cultured to determine the prevalences and concentrations of the following antimicrobial resistant bacteria (ARB): 3rd-generation cephalosporin-resistant (3GCr) Escherichia coli, cotrimoxazole-resistant (COTr) E. coli, tetracycline-resistant (TETr) E. coli, 3GCr Salmonella, and erythromycin-resistant (ERYr) Enterococcus spp. Genomic DNA was isolated from individual samples and pooled by lot. The abundances of aadA1, blaCMY, blaCTX-M, blaKPC-2, ermB, tetA, tetB, and tetM antimicrobial resistance genes (ARGs) were determined by qPCR. Genomic DNA was sequenced with an Illumina Nextseq to a mean depth of 90 million reads. Reads were queried against MEGARes, the Colorado State University database of 3,762 ARG variants. ARG abundances were reported in their ratio to 16s rRNA genes (16s normalized ARG abundance). Key Results: Prevalences of 3GCr E. coli and COTr E. coli were higher in CONV feces but their concentrations were below the limit of quantification for most samples (Table 1). Concentrations of TETr E. coli and ERYr Enterococcus spp. were higher in CONV feces (Table 2). By qPCR, 16s normalized ARG abundances were marginally higher in CONV feces (Table 3). 43 ARGs were detected by metagenomic sequencing. Metagenomic sequencing detected in all samples 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). By metagenomic sequencing, abundances of ARGs were higher in CONV feces than in RWA feces (Table 4). How can this information be applied in the industry? This study quantified the reductions in antimicrobial resistance due to RWA production practices. In general, the magnitudes of the reductions are small relative to the overall occurrences of antimicrobial resistance in cattle feces. These results will contribute to an increased understanding of the impact of antimicrobial uses during cattle production.