Are antimicrobial interventions associated with heat-resistant Escherichia coli on meat?

© Crown copyright 2020.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 Escherichia coli in the beef production chain is becoming more heat resistant due to those treatments. Cattle isolates (n=750) included seven serogroups (O157, O103, O111, O121, O145, O26, and O45) which were collected between 2002 and 2017. Beef plant isolates (n=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 E. coli at 60°C (D60C values) ranged from 0 to 7.54 min, with 97.2% of the values being<2 min. The prevalence of E. coli with D60C values of <2 min was not significantly different (P = 0.05) among cattle and meat plant isolates. E. coli from equipment before sanitation (median, 1.03 min) was more heat resistant than that after sanitation (median, 0.9 min). No significant difference in D60C values was observed among E. coli 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 D60C values than the LHR-negative isolates (3.25 versus 0.96 min). No increase in heat resistance in E. coli was observed along the beef production chain or with time.