Occurrence of antimicrobial-resistant Escherichia coli and Salmonella enterica in the beef cattle production and processing continuum

Abstract

Specific concerns have been raised that third-generation cephalosporin-resistant (3GCr) Escherichia coli, trimethoprim-sulfamethoxazole-resistant (COTr) E. coli, 3GCr Salmonella enterica, and nalidixic acid-resistant (NALr) S. enterica may be presentin cattle production environments, persist through beef processing, and contaminate final products. The prevalences and concentrationsof these organisms were determined in feces and hides (at feedlot and processing plant), pre-evisceration carcasses,and final carcasses from three lots of fed cattle (n=184). The prevalences and concentrations were further determined for striploins from 103 of the carcasses. 3GCr Salmonella was detected on 7.6% of hides during processing and was not detected on thefinal carcasses or strip loins. NALr S. enterica was detected on only one hide. 3GCr E. coli and COTr E. coli were detected on100.0% of hides during processing. Concentrations of 3GCr E. coli and COTr E. coli on hides were correlated with pre-eviscerationcarcass contamination. 3GCr E. coli and COTr E. coli were each detected on only 0.5% of final carcasses and were not detectedon strip loins. Five hundred and 42 isolates were screened for extraintestinal pathogenic E. coli (ExPEC) virulence-associatedmarkers. Only two COTr E. coli isolates from hides were ExPEC, indicating that fed cattle products are not a significantsource of ExPEC causing human urinary tract infections. The very low prevalences of these organisms on final carcasses andtheir absence on strip loins demonstrate that current sanitary dressing procedures and processing interventions are effectiveagainst antimicrobial-resistant bacteria.