The use of Whole genome sequencing (WGS) identified a multi-country outbreak of human listeriosis associated with consumption of frozen sweet corn produced in Hungary. The purpose of this report was to summarise information on the cases occurring in the UK which were part of this outbreak and outline investigations on the presence of Listeria monocytogenes in the affected food chain. Prior to the international recall of this product in 2018, 12 UK cases of listeriosis were identified as infected by the outbreak strain between 2015 and 18. Epidemiological and microbiological investigations confirmed these cases as belonging to the outbreak. A further case occurred in 2019 and a contaminated frozen pack from one of the implicated batches of sweet corn was recovered from the patient's domestic freezer. The outbreak strain was also detected in products from a sandwich manufacturer in 2018 which added frozen sweet corn directly to sandwich fillings. The sandwich manufacturer's sweet corn was supplied by a distributor in England which obtained frozen products from the Hungarian manufacturer implicated in the outbreak. Within the distributor's premises, 208 food and environmental samples were taken: L. monocytogenes was detected in 44% of 70 samples of frozen sweet corn and 5% of 79 other foods. The outbreak strain was detected in the frozen sweet corn, in one other frozen food (mixed vegetables) and in the factory environment. The outbreak strain was also recovered from frozen beans on retail sale in the first four months of 2019. Five other L. monocytogenes strains together with two other Listeria species were detected in samples from the importer's premises. One of the L. monocytogenes strains in the importer's factory, which was distinct from the outbreak strain, was also recovered from sweet corn collected from the sandwich manufacturer, sweet corn tested in England in 2013 and 2016 and the blood of two cases of human listeriosis which occurred in England in 2014. This report shows how analysis by WGS provides evidence to understand complex food chains. This report also highlights risks for transmission of human listeriosis from frozen sweet corn and the potential for misuse of this food as a ready-to-eat product.

全基因组测序（WGS）的使用确定了与食用匈牙利生产的冷冻甜玉米有关的多国人类李斯特菌病暴发。本报告的目的是总结此次爆发中在英国发生的病例的信息，并概述对单核细胞增生李斯特菌存在的调查在受影响的食物链中。在2018年该产品国际召回之前，在2015-18年之间，有12例英国李斯特菌病病例被确定为感染了流行毒株。流行病学和微生物学调查证实这些病例属于暴发。2019年又发生了一起病例，并从患者的家用冷冻柜中回收了涉及的一批甜玉米中被污染的冷冻包装。在2018年的三明治制造商的产品中也检测到暴发菌株，该产品将冷冻甜玉米直接添加到三明治馅料中。三明治制造商的甜玉米由英国的一家分销商提供，该分销商从匈牙利制造商那里获得了与爆发有关的冷冻产品。在分销商的场所内，采集了208个食品和环境样本：在70个冷冻甜玉米样品中有44％检出了单核细胞增生李斯特菌，在其他79种食品中检出了5％。在冷冻甜玉米，另一种冷冻食品（混合蔬菜）和工厂环境中检测到暴发菌株。暴发菌株还于2019年前四个月从零售的冷冻豆中回收。在进口商场所的样品中还检测到其他五种单核细胞增生李斯特菌菌株和其他两种李斯特菌。单核细胞增生李斯特菌之一进口商工厂的菌株与暴发菌株不同，还从三明治制造商收集的甜玉米中回收，2013年和2016年在英国测试了甜玉米，2014年在英国发生了两例人李斯特菌病的血液该报告显示了WGS的分析如何为理解复杂的食物链提供证据。该报告着重指出了冷冻甜玉米传播人类李斯特菌病的风险，以及将这种食物误食为即食产品的可能性。