Marshall J C, Soboleva T K, Jamieson P, French N P
Institute of Fundamental Sciences, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North 4474, New Zealand.
Ministry for Primary Industries, Pastoral House, The Terrace, Wellington 6011, New Zealand.
J Food Prot. 2016 May;79(5):771-80. doi: 10.4315/0362-028X.JFP-15-230.
Zoonotic bacteria such as Campylobacter, Listeria, and Shiga toxin-producing Escherichia coli have been found in bulk tank milk in many countries, and the consumption of raw milk has been implicated in outbreaks of disease in New Zealand. Fecal contamination at milking is probably the most common source of pathogenic bacteria in bulk tank milk. Raw milk was collected from 80 New Zealand dairy farms during 2011 and 2012 and tested periodically for Campylobacter, E. coli O157, Listeria monocytogenes, and Salmonella. Milk quality data such as coliform counts, total bacterial counts, and somatic cell counts also were collected. By treating the total bacterial count as a proxy for fecal contamination of milk and utilizing farm and animal level prevalence and shedding rates of each pathogen, a predictive model for the level of pathogenic bacteria in bulk tank raw milk was developed. The model utilizes a mixture distribution to combine the low level of contamination inherent in the milking process with isolated contamination events associated with significantly higher pathogen levels. By simulating the sampling and testing process, the predictive model was validated against the observed prevalence of each pathogen in the survey. The predicted prevalence was similar to the observed prevalence for E. coli O157 and Salmonella, although the predicted prevalence was higher than that observed in samples tested for Campylobacter.
在许多国家的大罐牛奶中都发现了人畜共患细菌，如弯曲杆菌、李斯特菌和产志贺毒素大肠杆菌，在新西兰，生牛奶的消费与疾病暴发有关。挤奶时的粪便污染可能是大罐牛奶中病原菌最常见的来源。2011年至2012年期间，从80个新西兰奶牛场采集了生牛奶，并定期检测弯曲杆菌、大肠杆菌O157、单核细胞增生李斯特菌和沙门氏菌。还收集了诸如大肠菌群计数、总细菌计数和体细胞计数等牛奶质量数据。通过将总细菌计数作为牛奶粪便污染的指标，并利用每个病原体在农场和动物层面的流行率及排出率，建立了一个大罐原料奶中病原菌水平的预测模型。该模型利用混合分布将挤奶过程中固有的低水平污染与与显著更高病原体水平相关的孤立污染事件结合起来。通过模拟采样和检测过程，根据调查中观察到的每种病原体的流行率对预测模型进行了验证。大肠杆菌O157和沙门氏菌的预测流行率与观察到的流行率相似，尽管弯曲杆菌检测样本的预测流行率高于观察到的流行率。
