Antimicrobial resistance in U.S. retail ground beef with and without label claims regarding antibiotic use

Authors: Schmidt, John; VIKRAM, AMIT - Intralytix, Inc; DOSTER, ENRIQUE - Colorado State University; THOMAS, KEVIN - Colorado State University; Weinroth, Margaret - Maggie; PARKER, JENNIFER - University Of Texas; HANES, AYANNA - Colorado State University; GEORNARAS, IFIGENIA - Colorado State University; MORLEY, PAUL - Texas A&M University; BELK, KEITH - Colorado State University; Wheeler, Tommy; Arthur, Terrance

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2020
Publication Date: 5/1/2021
Citation: Schmidt, J.W., Vikram, A., Doster, E., Thomas, K., Weinroth, M.D., Parker, J., Hanes, A., Geornaras, I., Morley, P.S., Belk, K.E., Wheeler, T.L., Arthur, T.M. 2021. Antimicrobial resistance in U.S. retail ground beef with and without label claims regarding antibiotic use. Journal of Food Protection. 84(5):827-842. https://doi.org/10.4315/JFP-20-376.
DOI: https://doi.org/10.4315/JFP-20-376

Interpretive Summary: Food-animal production accounts for about 77% of U.S. antibiotic use. Ground beef products with raised without antibiotics label claims are perceived to harbor lower antibiotic resistance levels than conventional products with no label claims regarding antibiotic use. Across six U.S. cities, 299 raised without antibiotics and 300 conventional ground beef samples were obtained at retail stores. Each sample was examined for 15 antibiotic resistances. Three antibiotic resistance levels were higher in conventional ground beef while 4 antibiotic resistance levels were higher in raised without antibiotics ground beef. These results indicate that antibiotic use during U.S. cattle production does not increase human exposure to antibiotic resistance via ground beef.

Technical Abstract: Antibiotics used during food animal production account for approximately 77% of U.S. antimicrobial consumption by mass. Ground beef products labeled as raised without antibiotics (RWA) are perceived to harbor lower levels of antimicrobial-resistant bacteria than conventional (CONV) products with no label claims regarding antimicrobial use. Retail ground beef samples were obtained from six U.S. cities. Samples with an RWA or U.S. Department of Agriculture Organic claim (n=299) were assigned to the RWA production system. Samples lacking these claims (n=300) were assigned to the CONV production system. Each sample was cultured for the detection of five antimicrobial-resistant bacteria. Genomic DNA was isolated from each sample, and a uantitative PCR assay was used to determine the abundance of 10 antimicrobial resistance (AMR) genes. Prevalence of tetracycline-resistant Escherichia coli (CONV, 46.3%; RWA, 34.4%; P < 0.01) and erythromycin-resistant Enterococcus (CONV, 48.0%; RWA, 37.5%; P = 0.01) was higher in CONV ground beef. Salmonella was detected in 1.2% of samples. The AMR gene blaCTX-M (CONV, 4.1 log-normalized abundance; RWA, 3.8 log-normalized abundance; P < 0.01) was more abundant in CONV ground beef. The AMR genes mecA (CONV, 4.4 log-normalized abundance; RWA, 4.9 log-normalized abundance; P = 0.05), tet(A) (CONV, 3.9 log-normalized abundance; RWA, 4.5 log-normalized abundance; P < 0.01), tet(B) (CONV, 3.9 log-normalized abundance; RWA, 4.5 log-normalized abundance; P < 0.01), and tet M) (CONV, 5.4 lognormalized abundance; RWA, 5.8 log-normalized abundance; P < 0.01) were more abundant in RWA ground beef. Although these results suggest that antimicrobial use during U.S. cattle production does not increase human exposure to antimicrobial-resistant bacteria via ground beef, quantitative microbiological risk assessments are required for authoritative determination of the human health impacts of the use of antimicrobial agents during beef production.