Quantitative risk assessment for verocytotoxigenic Escherichia coli in ground beef hamburgers in Argentina

SIGNORINI ML, HD TARABLA

Buenos Aires (Argentina)

Simposio; 7th International Symposium on Shiga Toxin (Verocytotoxin) Producing Escherichia coli Infections; 2009

Asociación Argentina de Microbiología

The objetctive of this study was to develop a quantitative risk assessment to model the E. coli VTEC contamination of beef hamburgers in Argentina. This is the first experience in Argentina adopting a far-to-table risk approach. The prevalence and counts of E. coli VTEC bacteria were modeled at various stages along the agri-food beef chain. The assessment considers initial contamination levels (only E. coli VTEC strains associated with HUS were considered); cross-contamination and decontamination events during the cattle slaughter process and the distribution, storage and consumption patterns in Argentina. One distinctive consumption patterns in Argetina was the habit of eating hamburgers prepared at home. The model was created in Microsoft Excel 2007 with the ad-on package @Risk (version 4.0, Palisade Corporation, New York, USA). The average pathogen dose ingested for adults and children were 30.96 CFU/kg hamburgers and 81.30 CFU/kg hamburgers, respectively. The data above were for hamburgers containing E. coli VTEC. The prevalence of hamburgers contaminated with the pathogen predicted by the model was found to be 1.82% (95% IC 2.55 x 10-8% to 14.9%). The model predicted an infection risk of 5.9x10-9 (95% IC 1.0x10-9 - 2.29x10-3), a probability of Hemolytic Uremic Syndrome (HUS) of 4.6x10-8 (95% IC 7.41x10-11 - 1.58x10-4) and a probability of mortality of 5.9x10-9 (95% IC 8.91x10-12 - 1.9x10-5) per meal for adult. The estimates per meal for child were 3.23x10-7 (95% IC 5.75x10-10 - 9.54x10-4), 1.8x10-8 (95% IC 3.23x10-11 - 5.24x10-5), and 6.31x10-10 (95% IC 8.91x10-13 - 2.29x10-6) for infection, HUS and mortality, respectively. The risk of infectin and HUS, were sensitive to the storage at home (r=-0.416), slaughterhouse storage temperature (r=0.240) and bacterial concentration in the cattle hide (r=0.239). The home-prepared hamburgers (r=-0.116) were associated with the risk of illness, although not as a result of their ingtrinsic characteristics but associated with the type of storage at retail (r=-0.110) and at home. The pathogen concentration in the cattle hide destined to slaughter was one of the most important factors associated with the risk of E. coli VTEC infection and HUS. Also, the temperature during the meat processing, and the thermal abuse during storage and food preparation, were determinant in the risk to infection and its consequences. These parameters were different depending on the type of hamburger consumed (comercial or home-prepared) and showed different risk of illness. This model will enable risk managers to adpt risk management measures on the appropiate steps identified in the sensitive analysis with the aim to reduce the E. coli VTEC risk, especially in those population where there is frequent consumtpion of hamburgers prepared at home.