Antibimicrobial susceptibility of trimethoprim-sulfamethoxazole and 3rd-generation cephalosporin-resistant Escherichia coli isolates enumerated longitudinally...

Authors: LONG, NATHAN - Texas Tech University; HALES, KRISTIN - Texas Tech University; BERRY, ELAINE - Former ARS Employee; LEGAKO, JERRAD - Texas Tech University; WOERNER, DALE - Texas Tech University; Broadway, Paul; Carroll, Jeffery - Jeff Carroll; Sanchez, Nicole; FERNANDO, SAMODHA - University Of Nebraska; Wells, James - Jim

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2023
Publication Date: 7/12/2023
Citation: Long, N.S., Hales, K.E., Berry, E.D., Legako, J.F., Woerner, D.R., Broadway, P.R., Carroll, J.A., Sanchez, N.C.B., Fernando, S.C., Wells, J.E. 2023. Antibimicrobial susceptibility of trimethoprim-sulfamethoxazole and 3rd-generation cephalosporin-resistant Escherichia coli isolates enumerated longitudinally from feedlot arrival to harvest in high-risk beef cattle administered common metaphylactic antimicrobials. Foodborne Pathogens and Disease. 20(7):252-260. https://doi.org/10.1089/fpd.2023.0001.
DOI: https://doi.org/10.1089/fpd.2023.0001

Interpretive Summary: Feedlot cattle that are of a high-risk to develop bovine respiratory disease (BRD) typically receive substantial antibiotic treatments when sick. To reduce the need to treat sick animals later, they often receive antimicrobials upon arrival to the feedlot. Therefore, BRD high-risk cattle are exposed to a variety of antimicrobials within the first month at the feedlot but little is known about antimicrobial resistant (AMR) Escherichia coli in these cattle. Fecal samples were collected over eight months from BRD high-risk cattle that were or were not treated with an antimicrobial at arrival to the feedlot and monitored for AMR in E. coli bacteria. Antimicrobial use at arrival resulted in increased AMR in the E coli populations for up to two months after arrival, but the AMR in E. coli at arrival and harvest were similar.

Technical Abstract: Multidrug resistant (MDR) Escherichia coli threaten the preservation of antimicrobials to treat infections in humans and livestock. Thus, it is important to understand where antimicrobial-resistant E. coli persist and factors that contribute to its their development. Crossbred cattle (n = 249; body weight = 244 kg –25 kg standard deviation) were blocked by arrival date and assigned metaphylactic antimicrobial treatments of sterile saline control, tulathromycin (TUL), ceftiofur, or florfenicol at random. Trimethoprim–sulfamethoxazole (COTR) and third-generation cephalosporin (CTXR)-resistant E. coli were isolated from fecal samples on days 0, 28, 56, 112, 182, and study END (day 252 for block 1 and day 242 for block 2). Then, susceptibility testing was conducted on all confirmed isolates. MDR was detected in both COTR and CTXR E. coli isolates. In COTR isolates, the number of antimicrobials each isolate was resistant to and the minimum inhibitory concentration (MIC) for amoxicillin–clavulanic acid, ceftriaxone, and gentamicin was greatest on day 28 compared with all other days ( p /= 0.07). In CTXR isolates, there was an effect of day for all antimicrobials tested except ampicillin and meropenem ( p