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Longitudinal Assessment of Prevalence and Incidence of Salmonella and Escherichia coli O157 Resistance to Antimicrobials in Feedlot Cattle Sourced and Finished in Two Different Regions of the United States.

Colten W DornbachKristin E HalesErin R GubbelsJames E WellsAshley A HoffmanAshlee N HanrattyDalton J LineTaylor M SmockJeff L ManahanZach S McDanielKesley B KohlNicole C Burdick SanchezJeffery A CarrollWarren C RuscheZachary K SmithPaul R Broadway
Published in: Foodborne pathogens and disease (2023)
The objective was to investigate the influence of cattle origin and region of finishing on the prevalence of Salmonella , Escherichia coli O157:H7, and select antimicrobial resistance in E. coli populations. Yearling heifers ( n  = 190) were utilized in a 2 × 2 factorial arrangement. After determining fecal Salmonella prevalence, heifers were sorted into one of four treatments: heifers originating from South Dakota (SD) and finished in SD (SD-SD); heifers originating from SD and finished in Texas (SD-TX); heifers originating from TX and finished in SD (TX-SD); and heifers originating from TX and finished in TX (TX-TX). Fecal, pen, and water scum line samples were collected longitudinally throughout the study; hide swab and subiliac lymph node (SLN) samples were collected at study end. A treatment × time interaction was observed ( p  ≤ 0.01) for fecal Salmonella prevalence, with prevalence being greatest for TX-TX and TX-SD heifers before transport. From day (d) 14 through study end, prevalence was greatest for TX-TX and SD-TX heifers compared with SD-SD and TX-SD heifers. Salmonella prevalence on hides were greater ( p  ≤ 0.01) for heifers finished in TX compared with SD. Salmonella prevalence in SLN tended ( p  = 0.06) to be greater in TX-TX and SD-TX heifers compared with TX-SD and SD-SD. Fecal E. coli O157:H7 prevalence had a treatment × time interaction ( p  = 0.04), with SD-TX prevalence being greater than TX-SD on d 56 and SD-SD and TX-TX being intermediate. A treatment × time interaction was observed for fecal trimethoprim-sulfamethoxazole-resistant and cefotaxime-resistant E. coli O157:H7 prevalence ( p  ≤ 0.01). Overall, these data suggest that the region of finishing influences pathogenic bacterial shedding patterns, with the initial 14 d after feedlot arrival being critical for pathogen carriage.
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