Location: Meat Safety and QualityTitle: Distribution of extremely heat resistant Escherichia coli in the beef production and processing continuum
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2022
Publication Date: N/A
Interpretive Summary: Some Escherichia coli (E. coli) have genes that allow them to resist high temperatures and other stressful conditions caused by beef processing treatments. Previous results suggested that E. coli like this were seldom found in cattle but present in beef products. To determine their source, E. coli collected from the same cattle at feedlots, at harvest, and after processing into strip loins were studied. Results confirmed the previous observations and found that the resistant E. coli were controlled by beef processing treatments. Their presence in strip loins is likely due to their ability to persist in the chilled environments of processing plants.
Technical Abstract: Understanding the dynamics of stress resistant Escherichia coli (E.coli) across the meat production and processing continuum is important for tracking sources of such microbes and devising effective modes of control. The Locus of Heat Resistance (LHR) is ~14-19Kb genetic element imparting extreme heat resistance (XHR) in Enterobacteriaceae. It has been hypothesized that thermal and antimicrobial interventions applied during meat processing may select for LHR+ E. coli. Thus, our goal was to study the prevalence and molecular biology of LHR+ E. coli amongst lots of beef cattle (n=3) from production through processing. Two hundred thirty-two generic E. coli isolated from the same animals through seven stages of the beef processing continuum (cattle in feedyards to packaged strip loins) were examined. LHR+ E. coli were rare (0.6%; 1 of 180) amongst the early stages of the beef continuum (feces and hides at feedlot, feces and hides at harvest, and pre-evisceration carcasses). Whereas the prevalence of LHR+ E. coli on final carcasses and strip loins was remarkably higher. Half (14 of 28) of the final carcass E. coli possessed the LHR, while 79.2% (19 of 24) of the strip loin E. coli did. Eighty five percent (29 of 34) of the LHR+ E. coli presented with the XHR phenotype. The selection or enrichment of LHR+ E. coli from harvest steps to the final products appeared unlikely as the LHR+ E. coli isolates were effectively controlled by antimicrobial interventions typically used during beef processing. Further, whole genome sequencing of the isolates suggested LHR+ E. coli are persisting in the chilled processing environment and that horizontal LHR transfer among E. coli isolates may take place.