Location: Meat Safety & Quality ResearchTitle: Antimicrobial resistance at two United States cull cow processing establishments
|VIKRAM, AMIT - Intralytix, Inc|
|BELK, KEITH - (NCE, CECR)networks Of Centres Of Exellence Of Canada, Centres Of Excellence For Commercilization A|
|MORLEY, PAUL - Texas A&M University|
|Weinroth, Margaret - Maggie|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2020
Publication Date: N/A
Interpretive Summary: Culled cows that supply cattle feeding operations with calves and culled dairy cows contribute about 18% of the cattle harvested in the U.S. each year. While published studies have demonstrated that antibiotic use has minimal effect on antibiotic resistance in fed cattle little data exists regarding cows. To address this data gap, carcass samples and feces were obtained from culled beef cows (conventional beef), culled dairy cows (conventional dairy), and culled organic dairy cows produced without using antibiotics (organic dairy) from two beef harvest and processing plants. At one plant, meat trimmings for ground beef also were sampled. Results indicate a few antibiotic resistance levels were higher in feces from conventional cows compared to organic cows. However, sample day had similar impacts on antibiotic resistance levels indicating that antibiotic use had only marginal impacts on antibiotic resistance levels. The impact of these marginally higher levels on human exposures to antibiotic resistance through beef is likely small since production without using antibiotics did not affect the levels of any measured antimicrobial resistance on beef products.
Technical Abstract: Culled beef cows (cows from cow-calf operations that have reached the end of productive life span) and culled dairy cows amount to approximately 18% of the cattle harvested in the U.S. annually. Several published studies have demonstrated that antimicrobial use has minimal effect on AMR levels in fed beef cattle, but data on U.S. cull cattle is extremely limited. To address this data gap, colon contents were obtained from 180 culled beef cows (conventional beef),179 culled dairy cows (conventional dairy), and 176 culled organic dairy cows produced without using antimicrobials (organic dairy). Also, 181 conventional beef, 173 conventional dairy, and 180 organic dairy carcasses were sponge sampled. These samples were obtained on 6 days (3 each at two beef harvest and processing establishments). At one establishment 30 samples of beef manufacturing trimmings (trim) from conventional cows and 30 samples of trim from organic dairy cows were acquired. All 1,129 samples were cultured for Escherichia coli, tetracycline-resistant (TET) E. coli, third-generation cephalosporin-resistant (3GCr) E. coli, Salmonella, and 3GCr Salmonella. Metagenomic DNA was isolated from 535 colon content samples and quantitative PCR was performed to assess the abundances of the following 10 antimicrobial resistance genes: aac(6’)-Ie-aph(2”)-Ia, aadA1, blaCMY-2, blaCTX-M, blaKPC-2, erm(B), mecA, tet(A), tet(B), and tet(M). For colon contents only TETr E. coli (P < 0.01), 3GCr E. coli (P < 0.01), and erm(B) (P = 0.03) levels were higher in conventional than organic cows. Sampling day also significantly (P < 0.01) affected each of these levels. The impact of these marginally higher levels on human AMR exposure through beef products is likely negligible since production system did not affect the levels of any measured antimicrobial resistance on carcasses or trim.