Simulating Escherichia coli O157:H7 transmission to assess effectiveness of interventions in Dutch dairy-beef slaughterhouses.

Beef contamination with Escherichia coli O157:H7 (VTEC) is an important food-safety issue. To investigate the effectiveness of interventions against VTEC in Dutch beef industrial slaughterhouses that slaughter 500 dairy cattle per day, a Monte Carlo simulation model was built. We examined seven carcass-antimicrobial interventions, namely: hot-water wash, lactic-acid rinse, trim, steam-vacuum, steam-pasteurization, hide-wash with ethanol and gamma irradiation, and their combinations. The estimated daily prevalence of contaminated beef-carcass quarters as the output of the model was 9.2%. Contaminated was defined as containing one or more CFU on the surface of a carcass quarter at the end of the quartering stage. Single interventions (except irradiation) could reduce the prevalence to from 6.2% to 1.7%, whereas the combination of interventions could lower it to from 1.2% to 0.1%. The most powerful intervention was irradiation, which could reduce the prevalence to <0.1%. The results of this study indicate that application of single interventions might be useful, although not sufficient. Hence, a combination of interventions along the slaughter process is the more promising approach to reduce the prevalence of contaminated beef quarters.