Resistance of E. coli from Beef to Decontaminating Treatments/Biocides

Shiga toxin-producing Escherichia coli (STEC), particularly STEC O157, are significant human pathogens, with cattle being identified as an important source. The infectious dose of STEC O157 is believed to be extremely low, such that exposure to a single cell may still represent a significant risk for potential infection. To reduce the contamination of beef with STEC O157, many beef processing plants in North America have employed various antimicrobial interventions, particularly during the carcass dressing process. Consequently, the level of E. coli on beef has been greatly reduced. In addition to decontaminating treatments for meat, biocides are also regularly applied to meat processing equipment as cleaning or sanitizing agents. Some concerns have been raised that these treatments may lead to increased level of resistance in E. coli and/or its persistence in meat processing environment. We investigated the response of E. coli originating from beef processing plants to commonly used decontaminating treatments and biocides for sanitation using a population based approach. No statistically significant difference in reductions by heat, acid or alkaline treatment was observed between E. coli populations originating from a plant where multiple antimicrobial interventions are routinely used and from a plant where no antimicrobial interventions are used. When two populations of E. coli, one persisting and the other transient, were assessed for their response to two sanitizers and one cleaning agent commonly used at food processing plants, the minimal inhibitory concentration and the minimal bactericidal concentration for the persisting group were not significantly higher than those for the transient group. Thus, the application of these treatments at beef processing plants does not seem to lead to elevated resistance in E. coli.