零膨胀模型在散装熟肉制品中单核细胞增生李斯特氏菌定量暴露评估中的应用

针对散装熟肉制品中单核细胞增生李斯特氏菌（简称单增李斯特菌）监测数据普遍存在的零膨胀和过度离散现象，探讨不同左删失数据处理方法对定量暴露评估的影响。2017年2—12月从上海市某区各大型超市、农贸市场及餐饮环节采集254 份散装熟肉制品进行单增李斯特菌定量检测。将检测结果与标准统计分布及其零膨胀模型相结合，利用R 2.0软件进行数据拟合，根据最优分布结果，确定零售阶段散装熟肉制品中单增李斯特菌的暴露情况。对于单增李斯特菌左删失数据的处理，优先构建零膨胀对数正态分布或零膨胀泊松对数正态分布。零膨胀模型的参数估计结果表明，散装熟肉制品中单增李斯特菌的阳性检出率为2%。本研究结果可为单增李斯特菌左删失数据的处理提供理论依据，并为完整的风险评估体系提供参考。

Application of Zero-Inflated Models in Quantitative Exposure Assessment of Listeria monocytogenes in Bulk Cooked Meat

In many cases, measured contamination levels of Listeria monocytogenes in bulk cooked meat are characterized by zero-inflation and over-dispersion features. The effect of different left-censored data processing methods on quantitative exposure assessment was discussed in this work. The contamination level of L. monocytogenes in bulk cooked meat products was determined using 254 samples collected from supermarkets, farmers’ markets and catering links in a certain district of Shanghai from February to December 2017. As an illustration, traditional statistical distributions and their zero-inflated models were used to assess the concentration of L. monocytogenes in bulk cooked meat products. The models were compared and validated for their performance using R 2.0 software. The L. monocytogenes concentration data consisting of a considerable number of left-censored data could be appropriately represented by zero-inflated lognormal distribution or zero-inflated Poisson lognormal distribution. The parameter estimates of the zero-inflated models indicated that the prevalence of L. monocytogenes in bulk cooked meat products was 2%. This work provides a theoretical basis for the statistical analysis of left-censored L. monocytogenes concentration data and serves as the essential starting point for a complete risk assessment framework.