Michael G. Gänzle
Department of Agricultural, Food and Nutritional Science, University of Alberta

Toxin producing and pathogenic bacteria are major contributors to foodborne illness. Foodborne pathogens continue to pose new challenges to agricultural food production, food processing, and public health. The emergence of new pathogens is linked to changing consumer habits, changes in agricultural production, novel technologies in food processing, the centralization of food processing, and the globalization of trade. The local occurrence of pathogenic bacteria or viruses often has global implications for food safety. Examples a recent outbreak of enterohaemorrhagic Escherichia coli in Canada, which resulted 16 cases of foodborne illness, in the recall of over 6000 tons of beef, and the closure of one of the biggest meat processing plant in Canada.
In North American beef processing facilities, commonly used pathogen intervention technologies for control of E. coli include steam pasteurization and carcass washes with lactic acid. However, several beef isolates of E. coli exhibit remarkable heat resistance and survive cooking of beef burger patties to a core temperature of 71°C [1]. Genome-wide transcriptome and proteome analyses demonstrated that heat resistance in E. coli AW1.7 is associated with altered membrane properties, and the over-expression of membrane proteins responsible for the transport of compatible solutes [2]. The heat resistance of E. coli AW1.7 is dependent on the presence of NaCl and the accumulation of compatible solutes, resulting in a higher thermal stability of ribosomes [3]. A large scale screening of enterohaemorrhagic E. coli revealed the presence of beef-associated pathogenic strains with comparable heat resistance. Initial results indicate that heat resistant E. coli also exhibit cross-resistance to high hydrostatic pressure [4] but are sensitive to lactic acid and phenolic acids.
Current pathogen intervention technologies in beef processing are thus not sufficient to eliminate EHEC during beef processing. Improved detection methods, improved plant hygiene and novel intervention technologies or antimicrobial agents will contribute to the control of EHEC on beef.