Are Antimicrobial Interventions Associated with Heat-Resistant Escherichia coli on Meat?

Decontamination practices, which often involve thermal treatments, are routinely performed in beef packing plants and have generally improved the safety of meat in North America. We investigated whether in the beef production chain is becoming more heat resistant due to those treatments. Cattle isolates ( = 750) included seven serogroups (O157, O103, O111, O121, O145, O26, and O45) which were collected between 2002 and 2017. Beef plant isolates ( = 700) from carcasses, fabrication equipment, and beef products were included. Heat resistance was determined in Luria-Bertani broth at 60°C and by PCR screening for the locus of heat resistance (LHR). The decimal reduction for at 60°C ( values) ranged from 0 to 7.54 min, with 97.2% of the values being <2 min. The prevalence of with values of >2 min was not significantly different (0.05) among cattle and meat plant isolates. from equipment before sanitation (median, 1.03 min) was more heat resistant than that after sanitation (median, 0.9 min). No significant difference in values was observed among isolates from different years, from carcasses before and after antimicrobial interventions, or from before and during carcass chilling. Of all isolates, 1.97% harbored LHR, and the LHR-positive isolates had greater median values than the LHR-negative isolates (3.25 versus 0.96 min). No increase in heat resistance in was observed along the beef production chain or with time. The implementation of multiple hurdles in the beef production chain has resulted in substantial improvement in the microbial safety of beef in Canada. In this study, we characterized a large number of isolates ( = 1,450) from various sources/stages of beef processing to determine whether the commonly used antimicrobial interventions would give rise to heat-resistant on meat, which in turn may require alternatives to the current control of pathogens and/or modifications to the current cooking recommendations for meat. The findings show that the degree and rate of heat resistance in did not increase along the production chain or with time. This furthers our understanding of man-made ecological niches that are required for the development of heat resistance in .