【作者】 田静；

【导师】 刘秀梅；

【作者基本信息】 中国疾病预防控制中心 ， 营养与食品卫生学， 2010， 博士

【摘要】 目的：单增李斯特菌是一种能引起人畜共患病的食源性致病菌。由于该菌污染食品种类较多,在冷藏温度下能够生长繁殖且引发疾病严重等特点,引起了世界范围内的广泛关注。本研究通过建立熟肉制品中单增李斯特菌的风险评估模型,对我国由熟肉制品中单增李斯特菌导致的疾病风险进行了半定量和定量评估,从而为国家主管机构建立针对单增李斯特菌的风险管理措施提供科学建议。方法：1.采用Risk Ranger方法对熟肉制品、非发酵豆制品及蔬菜沙拉中单增李斯特菌的风险进行半定量评估。2.采用@Risk软件建立了零售-消费阶段熟肉制品中单增李斯特菌的定量风险评估模型。分别对0-4岁、5-64岁及65岁以上人群消费散装熟肉制品和定型包装熟肉制品的患病风险进行了评估。3.应用定量风险评估中的剂量反应关系,对当熟肉制品中的单增李斯特菌设定不同的限量值时对患病风险的影响进行了假设性研究。4.根据风险评估结果和假设性研究结果,提出我国风险管理措施的建议。结果：1.采用Risk Ranger软件对熟肉制品、蔬菜沙拉和非发酵豆制品中单增李斯特菌的风险评分结果分别为61、52和57。熟肉制品／单增李斯特菌的风险最高,蔬菜沙拉／单增李斯特菌的风险最低。按照风险的相对值每增加6,风险的绝对值相当于增加10倍计算,由熟肉制品中单增李斯特菌导致的患病风险是非发酵豆制品的10倍,是蔬菜沙拉的32倍。2.定量评估的模型预测结果显示：0-4岁、5-64岁及65岁以上人群食入每份散装熟肉制品导致食源性李斯特氏菌病概率的中位数分别为6.50×10-11、2.13×10-12、9.05×10-11；每年引起每百万人患病的病例数的中位数分别为5.53×10-3、1.72×10-4、7.57×10-3。0-4岁、5-64岁及65岁以上人群食入每份定型包装熟肉制品引起李斯特菌病患病概率的中位数分别为：6.51×10-7、1.96×10-8、8.63×10-7；每年引起每百万人患病的病例数的中位数分别为55.9、1.69、71.2。3.敏感性分析结果显示：零售时熟肉制品中单增李斯特菌的污染状况、每份熟肉制品的摄入量、家庭贮存时间、家庭贮存温度及5℃的EGR与患病风险的关系均是正相关。对于散装熟肉制品,零售时产品中致病菌的污染情况对风险的影响最大；对于定型包装熟肉制品,人群食入每份产品的量对风险的影响最大。4.贮存温度和时间对模型结果影响的研究显示：在夏季室温放置三天后,散装熟肉制品中单增李斯特菌增长的中位数为5.75 log CFU/g(0.62 log CFU/g-17.53 log CFU/g),摄入每份食品患病概率的中位数为1.97×10-5(1.02×101-10～1.24×10-2)；在春秋季室温放置三天后,散装熟肉制品中单增李斯特菌增长的中位数为3.44 log CFU/g(0.36 log CFU/g-10.871og CFU/g),摄入每份食品患病概率的中位数为1.01×10-7 (4.20×10-11-6.43×10-3)。比较不同季节室温放置熟肉制品的结果可见,夏季室温放置熟肉制品引起的单增李斯特菌增长及患病概率要高于春秋季(高出2个数量级)。5.对熟肉制品中单增李斯特菌限量值的假设性研究结果显示：在假定的非阈值模型情况下对熟肉制品中的单增李斯特菌进行分析时,随着污染率或污染程度的增加,其风险和预计的李斯特氏菌的病例数也相应增加。理论上讲,10万份单增李斯特菌的污染程度达100 CFU／g食品的患病风险,与1份污染程度达107CFU／g的食品的致病结果是一样的。当将标准限量设定为<0.04 CFU／g和100CFU／g时,在产品不同缺陷比例下引起的患病例数基本相同。结论：1.采用Risk Ranger软件对熟肉制品／单增李斯特菌、非发酵豆制品／单增李斯特菌及蔬菜沙拉单增李斯特菌三种即食食品／单增李斯特菌组合的风险分级结果显示,熟肉制品是发生李斯特菌病的高危食品。2.采用@Risk软件的评估结果显示,无论是对于定型包装熟肉制品还是散装熟肉制品,0-4岁和65岁以上两组人群比5-64岁人群更为易感,每份食品引起的患病概率比普通人群高一个数量级。从评估结果的概率分布图可以看出,消费者摄入的李斯特菌的数量与风险评估结果成正比。因此,有理由认为任何能降低暴露的战略措施均可降低风险。3.贮存温度和时间对模型结果影响的探讨性研究结果显示,无论夏季还是春秋季,如果将熟肉制品放置在室温下,单增李斯特菌将呈几何倍数快速增长。进一步证明了低温冷藏可以显著降低单增李斯特菌的生长繁殖。热处理对模型结果影响的研究显示,70℃加热几分钟就可以杀灭熟肉制品中的李斯特菌。提示消费者通过消费前热处理可以有效地降低或防止李斯特氏菌病的发生。4.定量评估模型的不确定性分析结果显示,由于数据的不完善以及检测方法的限制,在评估过程中有可能高估了消费定型包装熟肉制品引起的李斯特氏菌病的概率。5.根据定量评估结果,提示风险管理者参考评估结果,结合散装熟肉制品和定型包装熟肉制品在加工方式、消费模式等方面的特点,制定不同的风险管理措施。6.对熟肉制品中单增李斯特菌的风险管理措施包括：(1)制定微生物限量标准,建议将定型包装熟肉制品中单增李斯特菌的限量标准定为n=5,c=0,m=0／25g,散装熟肉制品暂不制定限量标准；(2)修订、整合与熟肉制品相关的规范；(3)加强过程控制,对原料、加工过程、包装前、包装后、消费前产品中的单增李斯特菌进行控制；(4)对监管人员、医务工作者、食品加工者及消费者开展教育培训。通过这些管理措施降低产品中的单增李斯特菌含量,最终达到保护消费者健康的目的。更多还原

【Abstract】 Objective:Listeria monocytogenes is a foodborne pathogen which can cause zoonotic disease. The pathogen could contaminate many types of foods, grow and reproduce in cold temperatures and lead to severe disease. In view of these characteristics of the bacteria, it caused widespread concern around the world. In this study, risk assessment model of Listeria monocytogenes in cooked meat products has been established. The semi-quantitative and quantitative assessment for Listeria monocytogenes in cooked meats in China have been conducted through the models, so as to provide national authorities with the scientific advice on risk management measures of controlling risk caused by Listeria monocytogenes.Method:1.Using Risk Ranger software to conduct the semi-quantitative assessment of Listeria monocytogenes in the cooked meats, vegetables salads and non-fermented soybean products.2.Using @Risk software to build a quantitative risk assessment model of Listeria monocytogenes in cooked meats at the retail-consumption step. The risk of listeriosis caused by consuming deli meats and packaged meats for different sub-population (0-4 years old,5-64 years old, and 65 years and older) was estimated respectively.3.Based on the dose-response relationship in quantitative risk assessment, the hypothetical scenario study was conducted in order to explore the impact of disease risk when setting different limits for Listeria monocytogenes in the cooked meats.4.Considering the risk assessment and hypothetical research results, propose the suggestions on risk management measures in China.Results:1.Relative risk for Listeria monocytogenes in cooked meats, vegetable salads and non-fermented soybean products is 61,52 and 57,respectively. Cooked meats/ Listeria monocytogenes pairs is at the highest risk, vegetable salad/Listeria monocytogenes pairs is at the lowest risk. When the relative risk increases 6,the absolute risk will increase 10 times.According to this conversion relationship, risk from cooked meats/Listeria monocytogenes is 10 times than risk from non-fermented soybean products and is 32 times than that of the vegetables salads.2.The model prediction results from quantitative risk assessment show that:estimated probability (median) of listeriosis incidence caused by deli meats per serving in young (0-4 years old),intermediate age (5-64 years old) and elderly (65 years and older) is 6.50×10-11,2.13×10-12 and 9.05×10-11,respectively;estimated number of cases (median) of listeriosis each year per million people for deli meats in young, intermediate age and elderly population is 5.53×10-3,1.72×10-4 and 7.57×10-3.For the package cooked meats, estimated probability (median) of listeriosis incidence in young, intermediate age, elderly and total population is 6.51×10-7,1.96×10-8 and 8.63×10-7; estimated number of cases (median) of listeriosis each year per million for corresponding sub-population is 55.9,1.69 and 71.2,respectively.3.Results of sensitivity analysis show that:contamination level at retail, serving size of cooked meat, storage time at home,storage temperature and EGR at 5℃are positive factors for the risk of listeriosis. For deli meats, contamination level at retail is the most relative factor. As for the packaged cooked meats, serving size will significantly affect the risk results.4.The impact of model resulted from storage temperature and time show that:when the deli meats are at the environment in the summer, concentration of Listeria monocytogenes will increase 5.75 log CFU/g (0.62 log CFU/g-17.531og CFU/g) after three days, probability of listeriosis incidence caused by deli meats per serving is 1.97×10-5 (1.02×10-10-1.24×10-2);if these deli meats are placed at environment in the spring and autumn, concentration of Listeria monocytogenes would increase 3.44 log CFU/g (0.36 log CFU/g-10.87 log CFU/g) after three days, probability of listeriosis incidence caused by deli meats per serving is 1.01×10-7 (4.20×10-11-6.43×10-3).By the comparison, results from the former (in the summer) are two orders of magnitude higher than the latter (in the spring and autumn). 5.Hypothetical research results for Listeria monocytogenes in cooked meat products show that:in the supposed non-threshold model, when the concentrations of Listeria monocytogenes in the cooked meats increase, the risk and expected number of cases of Listeriosis also increase.In theory, the effect of introducing into the food supply 10 0000 servings contaminated with Listeria monocytogenes at a level of 100 CFU/g could be compensated by removing from the food supply a single serving contaminated at level of 107 CFU/g.When the microbiological limit is set at<0.04 CFU/g and 100 CFU/g, the number of cases of listeriosis are the similar at the different defective percentage for packaged cooked meats.Conclusion:1.Using Risk Ranger software, we could obtain the results for risk ranking from cooked meat/Listeria monocytogenes, non-fermented soybean products/Listeria monocytogenes and vegetable salads/Listeria monocytogenes.The results show that cooked meat is a high risk food for listeriosis.2.Predicted results by using @ Risk software show that:the risk caused by packaged cooked meat products is higher than that of the deli meats. For deli meats and packaged cooked meat, young group and elder group are more susceptible than the intermediate-age group. Probability of foodborne illness caused by per serving food in these two groups is one order of magnitude higher than that of intermediate-age group. From the probability distribution of the evaluation results, it could obtain the conclusion that the consumer intake level of Listeria monocytogenes is proportional to the results of risk assessment. Therefore, we could believe that any strategic measures which could reduce exposure will reduce the risk.3.Result from study on storage temperature and time show that, regardless of the summer or fall, if the cooked meat left at room temperature, Listeria monocytogenes will show multiple rapid growths. Further evidences show that cold storage can significantly reduce growth and reproduction of Listeria monocytogenes.Influence of heat treatment on results of assessment model show, if heat treatment process at 70℃could last a few minutes, it will kill Listeria monocytogenes in cooked meats. It reminders that it is possible for consumers to effectively reduce or prevent the foodborne lisiteriosis by the heat treatment before consumption.4.Uncertainty analysis results of model from quantitative assessment reveal that, due to incomplete data and the detection limit of method, it may overestimate risk caused by consuming the packaged cooked meats in the assessment process.5.According to the risk assessment results, we suggest that risk managers should confirm the different risk management measures for deli meats and packaged cooked meats, with considering the different processing ways, consumption patterns and other characteristics.6.The suggestion on risk management measures for the listeria monocytogenes in the cooked meats are as follows:(1)Establish microbiological limits in finish products. We propose that standard of Listeria monocytogenes in packaged cooked meats is n= 5,c=0, m=0/25g and not to establish the standard for this pathogen in deli meats.(2) Revise and integrate the cooked meat-related code of practice; (3)Strengthen process control, and especially control listeria monocytogenes at the following steps (raw materials, processing, pre-packing, post-packing and pre-consumption); (4) Carry out education and training for supervision personnel, medical workers, food processors and consumers.Reduce the levels of listeria monocytogenes and ultimately protect consumer health by these management measures.更多还原