Process risk modelling review

Summary

Escherichia coli O157:H7 and Salmonella are both food-borne pathogens of humans that can be found in the gut of healthy livestock. Cattle are considered one of the main reservoirs of E. coli O157:H7 and consumption of under-cooked beef products has been identified as a cause of human disease due to this pathogen. A factor that determines the proportion of humans who become ill after exposure to Salmonella or E. coli O157:H7 in food is the number of viable cells ingested. Thus knowledge of the concentration of the pathogen at various stages of cattle production, beef processing, food preparation and consumption is of critical importance in assessing risk of human disease due to these pathogens.
Methods for accurately enumerating E. coli O157:H7 and Salmonella provide an opportunity to explore the above relationship.The technique involved combining the most probable number method (MPN) with immunomagnetic separation (IMS) 1 ,2.A major advantage of this approach was the ability to quantify the amount of pathogen when only small numbers are present. A disadvantage of this approach was the accuracy of the MPN method itself.
In this work we therefore aimed to describe the relationship between counts of generic E. coli, E. coli O157:H7 and Salmonella spp. in naturally contaminated cattle faeces and on beef carcases during a commercial slaughter process. Where useful relationships are found we attempted to express them in a probabilistic fashion for use in a quantitative risk model. The analysis performed on existing data where the Salmonella and E. coli O157:H7 concentration component were generated by the combination of MPN and IMS.