鸡蛋表面肠炎沙门氏菌的随机暴露模型构建

Shell egg is the common vehicle of Salmonella Enteritidis and frequently associated with salmonellosis outbreaks. The bacterial growth and/or survival on eggshell and cross-contamination would happen due to the inappropriate home storage and handling methods in kitchen, respectively. In nowadays, the predictive models in different storage conditions and cross-contamination have been recognized as the most important data gap in risk assessment model. In this project, we try to: 1) model the growth and/or survival of Salmonella Enteritidis on eggshell to figure out the dynamic pattern of bacterial contamination when storage in constant temperature and fluctuant temperatures; 2) characterize the probability of cross-contamination and the bacterial transfer rate of various handling scenarios to explore the relationship of cross-contamination probability and bacterial transfer rate with the initial contamination level, contact times and etc.; 3) establish the probabilistic exposure model of “storage, egg crack, hand washing and cutting” in house and simulate with Monte Carlo method to describe the uncertainty and variability of the results. The technical route and research methods are reasonable. We have strong relative background, superior research conditions and well-integrated work assignment. Our research could clearly determine the risk factors in kitchen and propose guidelines of home storage and handling methods for consumers. Beside, our research could provide valuable models and data for risk assessment of Salmonella Enteritidis, which would be of great importance significant in improving the microbial risk assessment in China.

鸡蛋是引起沙门氏菌疾病的最常见食物之一，储藏和处理方式不当会造成蛋壳表面的细菌污染变化和交叉污染，成为食品安全隐患。储藏环节的预测模型和厨房中的交叉污染是目前鸡蛋沙门氏菌风险评估中缺失的重要数据资料。本研究拟构建蛋壳表面肠炎沙门氏菌在不同储藏方式下的预测模型，明确细菌在恒温和温度波动等情况下的污染变化规律，研究各情景中交叉污染的发生概率和细菌迁移率，探索初始污染水平、接触时间、接触次数等与交叉污染概率和细菌迁移率的定量关系，在此基础上建立家庭“储藏、打蛋、洗手、切菜”过程蛋壳表面肠炎沙门氏菌暴露模型，以概率分布定义模型输入量，基于蒙特卡洛分析，描述模型的不确定性和变异性。本研究的技术路线和方法可行，工作基础和条件扎实，人员分工合理。本项目可明确家庭关键风险因子，引导消费者合理储藏和处理鲜蛋，同时为建立鸡蛋沙门氏菌风险评估模型提供数据资料，对推进我国定量微生物风险评估研究具有重要意义。

鸡蛋是引起人群沙门菌疾病的常见食物之一，虽然我国居民具有熟食鸡蛋的消费习惯，但不恰当的储藏和处理方式会造成细菌交叉污染，造成消费隐患，掌握鸡蛋表面沙门氏菌在储藏过程的污染变化和厨房环节的交叉污染规律，明确关键风险因子，对引导消费者正确处理食物、保障消费安全具有重要意义。本研究重点围绕以蛋壳表面沙门氏菌污染，探索不同储藏条件、清洗方式下细菌暴露水平的变化规律，运用预测微生物学、概率分布拟合等手段构建了细菌在各种情景下的生长/衰亡模型；研究了打蛋行为细菌交叉污染的迁移率；在此基础上构建了鸡蛋在“储藏、打蛋、洗手、切菜”过程中沙门氏菌模块式随机暴露评估模型，基于敏感性分析，明确影响细菌暴露水平的显著性因素。评估结果表明，打蛋后迁移至食物表面的沙门菌最终污染平均值仅为7.27E-5 log CFU/g，健康风险低，但手表面的平均污染水平为1.45log CFU/g，健康风险较高；传统恒温储藏条件下构建的预测模型会过高估计风险最大值（是基线模型的1.71倍），波动温度预测模型应被用于暴露评估中；对消费者而言，打蛋后洗手是影响最终食物表面细菌污染水平的最主要因素；对大范围人群而言，打蛋后洗手行为概率和冷藏行为概率，是影响人群食物中毒风险的最重要因素。本项目的研究结果可为科学指导家庭消费提供理论依据。