ABSTRACT

Due to its high case fatality rate, foodborne listeriosis is considered a major public health concern worldwide. We describe one of the largest listeriosis outbreaks in Germany with 83 cases of invasive listeriosis between 2013 and 2018. As part of the outbreak investigation, we identified a highly diverse Listeria monocytogenes population at a single producer of ready-to-eat meat products. Strikingly, the extensive sampling after identification of a first match between a cluster of clinical isolates and a food isolate allowed for a linkage between this producer and a second, previously unmatched cluster of clinical isolates. Bacterial persistence in the processing plant and indications of cross-contamination events explained long-term contamination of food that led to the protracted outbreak. Based on screening for virulence factors, a pathogenic phenotype could not be ruled out for other strains circulating in the plant, suggesting that the outbreak could have been even larger. As most isolates were sensitive to common biocides used in the plant, hard to clean niches in the production line may have played a major role in the consolidation of the contamination. Our study demonstrates how important it is to search for the origin of infection when cases of illness have occurred (backtracking), but also clearly highlights that it is equally important to check whether a contamination at food or production level has caused disease (forward checking). Only through this two-sided control strategy, foodborne disease outbreaks such as listeriosis can be minimized, which could be a real improvement for public health.

摘要

由于食源性李斯特菌病的高病死率，被认为是世界范围内主要的公共卫生问题。我们描述了德国最大的李斯特菌病暴发之一，在2013年至2018年之间发生了83例侵袭性李斯特菌病。作为暴发调查的一部分，我们确定了高度多样化的单核细胞增生李斯特菌单一即食肉制品生产商的人口数量。令人惊讶的是，在鉴定出临床分离菌群和食品分离菌之间的首次匹配后，进行了广泛的采样，从而使该生产者与先前未匹配的第二株临床分离菌之间建立了联系。加工厂中的细菌残留和交叉污染事件的迹象解释了食品的长期污染，导致了长期爆发。根据对毒力因子的筛选，不能排除植物中循环传播的其他菌株的致病表型，这表明爆发可能更大。由于大多数分离株对工厂中使用的常用杀生物剂敏感，因此难以清洁生产线中的生态位可能在污染合并中起了主要作用。我们的研究表明，在发生疾病病例时（回溯）寻找感染源非常重要，但也明确强调，检查食品或生产水平的污染是否引起疾病同等重要（向前检查） 。只有通过这种双向控制策略，才能将食源性疾病如李斯特菌病的暴发降至最低，这才是对公共卫生的真正改善。