Listeriosis is a foodborne illness characterized by a relatively low morbidity, but a large disease burden due to the severity of clinical manifestations and the high case fatality rate. Increased listeriosis notifications have been observed in Europe since the 2000s. However, the reasons for this increase are largely unknown, with the sources of sporadic human listerioris often remaining elusive. Here we inferred the relative contributions of several putative sources of Listeria monocytogenes strains from listerioris patients in Northern Italy (Piedmont and Lombardy regions), using two established source attribution models (i.e. ‘Dutch’ and ‘STRUCTURE’) in comparative fashion. We compared the Multi-Locus Sequence Typing and Multi-Virulence-Locus Sequence Typing profiles of strains collected from beef, dairy, fish, game, mixed foods, mixed meat, pork, and poultry. Overall, 634 L. monocytogenes isolates were collected from 2005 to 2016. In total, 40 clonal complexes and 51 virulence types were identified, with 36% of the isolates belonging to possible epidemic clones (i.e. genetically related strains from unrelated outbreaks). Source attribution analysis showed that 50% of human listerioris cases (95% Confidence Interval 44-55%) could be attributed to dairy products, followed by poultry and pork (15% each), and mixed foods (15%). Since the contamination of dairy, poultry and pork products are closely linked to primary production, expanding actions currently limited to ready-to-eat products to the reservoir level may help reducing the risk of cross-contamination at the consumer level.

李斯特氏菌病是一种食源性疾病，其特点是发病率相对较低，但由于临床表现的严重性和高病死率而导致疾病负担大。自2000年代以来，在欧洲观察到李斯特菌病的通报有所增加。但是，这种增加的原因在很大程度上尚不清楚，因为零星的人类李斯特氏菌的来源常常难以捉摸。在这里，我们推断李斯特菌的几种推定来源的相对贡献来自意大利北部（皮埃蒙特和伦巴第地区）的李斯特氏菌病菌的菌株，使用两种建立的来源归因模型（即“荷兰”和“结构”）以比较方式进行。我们比较了从牛肉，乳制品，鱼，野味，混合食品，混合肉，猪肉和家禽中收集的菌株的多基因座序列分型和多毒力基因座序列分型。总共634种单核细胞增生李斯特菌从2005年至2016年收集了分离株。总共鉴定出40种克隆复合体和51种毒力类型，其中36％的分离株属于可能的流行克隆（即来自无关疫情的遗传相关菌株）。来源归因分析显示，人类李斯特氏菌病例中有50％（95％的置信区间44-55％）可归因于乳制品，其次是禽肉和猪肉（各占15％）和混合食品（15％）。由于乳制品，家禽和猪肉产品的污染与初级生产密切相关，因此将目前仅限于即食产品的行动扩大到水库一级，可能有助于减少消费者一级的交叉污染风险。