Nofima, Norwegian Institute of Food, Fisheries, and Aquaculture Research, Ås, Norway.
Unit for Food Microbiology, Institute for Food Safety, Food Technology and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria.
Appl Environ Microbiol. 2022 Sep 22;88(18):e0086122. doi: 10.1128/aem.00861-22. Epub 2022 Aug 25.
To investigate the diversity, distribution, persistence, and prevalence of stress survival and resistance genes of Listeria monocytogenes clones dominating in food processing environments in Norway, genome sequences from 769 L. monocytogenes isolates from food industry environments, foods, and raw materials (512 of which were sequenced in the present study) were subjected to whole-genome multilocus sequence typing (wgMLST), single-nucleotide polymorphism (SNP), and comparative genomic analyses. The data set comprised isolates from nine meat and six salmon processing facilities in Norway collected over a period of three decades. The most prevalent clonal complex (CC) was CC121, found in 10 factories, followed by CC7, CC8, and CC9, found in 7 factories each. Overall, 72% of the isolates were classified as persistent, showing 20 or fewer wgMLST allelic differences toward an isolate found in the same factory in a different calendar year. Moreover, over half of the isolates (56%) showed this level of genetic similarity toward an isolate collected from a different food processing facility. These were designated as pervasive strains, defined as clusters with the same level of genetic similarity as persistent strains but isolated from different factories. The prevalence of genetic determinants associated with increased survival in food processing environments, including heavy metal and biocide resistance determinants, stress response genes, and truncation mutations, showed a highly significant increase among pervasive isolates but not among persistent isolates. Furthermore, these genes were significantly more prevalent among the isolates from food processing environments compared to in isolates from natural and rural environments ( = 218) and clinical isolates ( = 111) from Norway. Listeria monocytogenes can persist in food processing environments for months to decades and spread through the food system by, e.g., contaminated raw materials. Knowledge of the distribution and diversity of L. monocytogenes is important in outbreak investigations and is essential to effectively track and control this pathogen in the food system. The present study presents a comprehensive overview of the prevalence of persistent clones and of the diversity of L. monocytogenes in Norwegian food processing facilities. The results demonstrate extensive spread of highly similar strains throughout the Norwegian food system, in that 56% of the 769 collected isolates from food processing factories belonged to clusters of L. monocytogenes identified in more than one facility. These strains were associated with an overall increase in the prevalence of plasmids and determinants of heavy metal and biocide resistance, as well as other genetic elements associated with stress survival mechanisms and persistence.
为了研究在挪威食品加工环境中占主导地位的单核细胞增生李斯特菌克隆的多样性、分布、持久性和流行情况，对来自食品工业环境、食品和原材料的 769 株单核细胞增生李斯特菌分离株的基因组序列（其中 512 株在本研究中进行了测序）进行了全基因组多位点序列分型（wgMLST）、单核苷酸多态性（SNP）和比较基因组分析。该数据集包括来自挪威 9 个肉类和 6 个三文鱼加工工厂的分离株，这些分离株是在过去 30 年中收集的。最常见的克隆复合体（CC）是 CC121，在 10 个工厂中发现，其次是 CC7、CC8 和 CC9，在 7 个工厂中发现。总体而言，72%的分离株被归类为持久性分离株，与同一工厂不同年份发现的分离株相比，其 wgMLST 等位基因差异为 20 个或更少。此外，超过一半的分离株（56%）与来自不同食品加工设施的分离株具有相同水平的遗传相似性。这些被指定为普遍菌株，定义为与持久性菌株具有相同遗传相似性的集群，但分离自不同工厂。在食品加工环境中具有更高生存能力的遗传决定因素（包括重金属和杀生物剂抗性决定因素、应激反应基因和截断突变）的流行率在普遍分离株中显著增加，但在持久性分离株中没有增加。此外，与来自挪威的天然和农村环境（=218）以及临床分离株（=111）相比，这些基因在食品加工环境中的分离株中更为普遍。单核细胞增生李斯特菌可以在食品加工环境中存活数月至数十年，并通过污染的原材料等在食品系统中传播。了解单核细胞增生李斯特菌的分布和多样性对于暴发调查很重要，对于有效跟踪和控制食品系统中的这种病原体至关重要。本研究全面概述了挪威食品加工设施中持久性克隆的流行情况和单核细胞增生李斯特菌的多样性。结果表明，高度相似的菌株在整个挪威食品系统中广泛传播，在所收集的 769 株来自食品加工厂的分离株中，有 56%属于在一个以上工厂中发现的单核细胞增生李斯特菌集群。这些菌株与质粒和重金属及杀生物剂抗性决定因素以及其他与应激生存机制和持久性相关的遗传元件的流行率总体增加有关。
