Location: Meat Safety & Quality ResearchTitle: Similar levels of antimicrobial resistance in United States foodservice ground beef products with and without a "Raised Without Antibiotics" claim Author
Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2018
Publication Date: N/A
Interpretive Summary: Meat products, including ground beef, are thought to be routes of transmission for antibiotic resistance from animals to humans. Ground beef products produced from cattle "raised without antibiotics" (RWA) are perceived as harboring lower levels of antibiotic resistance than "conventional" (CONV) products which may contain meat from animals that received antibiotics. However, no study has examined antibiotic resistance levels in United States (U.S.) ground beef since a small study published in 2004. This study found that the microbial flora and antibiotic resistance levels of CONV and RWA ground beef were similar. These results demonstrate that RWA ground beef does not deliver its major perceived benefit, lower levels of antibiotic resistance than CONV ground beef. These results were consistent with prior research demonstrating that the long-term antibiotic resistance impacts of antibiotic uses during U.S. beef cattle production are minimal and indicate a need for reevaluation of the claims of the detrimental impact of antibiotic uses during U.S. beef cattle production on human health via ground beef.
Technical Abstract: Meat products, including ground beef, with "Raised Without Antibiotics" (RWA) label claims are believed to harbor less antimicrobial resistance (AMR) than "Conventional" (CONV) products with no such label claim. However, the relative levels of AMR in United States (U.S.) CONV and RWA ground beef have not been recently assessed. A total of 370 ground beef (191 CONV and 179 RWA) samples were collected monthly over 13 months from three foodservice suppliers that provide both CONV and RWA ground beef. The following antibiotic resistant bacteria were cultured: tetracycline-resistant (TETr) Escherichia coli, 3rd-generation cephalosporin-resistant (3GCr) E. coli, TETr Salmonella enterica, 3GCr S. enterica, nalidixic acid-resistant (NALr) S. enterica, erythromycin-resistant (ERYr) Enterococcus spp., TETr Enterococcus spp., and methicillin-resistant Staphylococcus aureus. Only TETr E. coli was more frequently detected in CONV ground beef (CONV = 54.2%, RWA = 35.2%, P < 0.01). Metagenomic DNA was isolated from each sample and equal amounts of metagenomic DNA was pooled by supplier, month, and production system (CONV or RWA) for a total of 75 pooled samples (38 CONV, 37 RWA). The levels of aac(6')-Ie-aph(2")-Ia, aadA1, blaCMY-2, blaCTX-M, blaKPC-2, erm(B), mecA, tet(A), tet(B), and tet(M) were assessed by qPCR. The only differences detected were tet(A) (2.9-log2 fold change, P = 0.04) and tet(B) (5.6-log2 fold change, P = 0.03) were significantly more abundant in RWA ground beef. 16S rRNA gene phylogenetic analyses found that ground beef microbiomes differed more by supplier than by production system.