Quantitative Microbiological Risk Assessment of Nontyphoidal Salmonella in Ground Pork from China and Broiler Chickens from Canada

學生姓名: 蕭淮安
指導教授: 凌明沛
學期: 111上
摘　　要: Foodborne disease caused by nontyphoidal Salmonella (NTS) is one of the most important food safety issues worldwide. Salmonella Heidelberg resistant to ceftiofur (a third-generation cephalosporin antimicrobial agent) posed a risk to public health in Canada. The objectives of this study were to carry out microbial monitoring on the prevalence of NTS in commercial ground pork and S. Heidelberg in broiler chicken, investigate consumption patterns, and conduct a quantitative microbiological risk assessment (QMRA). The results showed that the prevalence of NTS in ground pork purchased in Chengdu was 69.64% (95% confidence interval [CI], 60.2–78.0), with a mean contamination level of −0.164 log CFU/g. After general cooking, NTS in ground pork could be eliminated (contamination level of zero). The estimated probability of causing salmonellosis per day was 9.43E-06 (95% CI: 8.82E-06–1.00E-05), while the estimated salmonellosis cases per million people per year were 3442 (95% CI: 3218– 3666). The risk in Canada was reduced by 90% or 20% when two separate scenarios designed to capture the effect of withdrawing preventive ceftiofur use from poultry production were simulated using different approaches; A 50% reduction in the probability of human prior exposure to antimicrobials, which has a selective and competitive effect for Salmonella spp. following ingestion of contaminated products, reduced the risk by 65%. Other promising measures that could be considered for further risk management included improved cleaning and disinfection between broiler flocks on farm (risk reduction by 26%), exclusive use of air chilling (risk reduction by 34%), and the improvement of meat storage and preparation conditions, e.g., no temperature abuse at retail (risk reduction by 88%). These findings showed the importance of a structured approach to assessing and potentially implementing effective interventions to reduce the risk associated with ceftiofur-resistant S. Heidelberg at different steps along the agri35 food chain.