An outbreak of human listeriosis associated with frozen sweet corn consumption: Investigations in the UK

• Published in: International journal of food microbiology Vol. 338; p. 108994
• Main Authors: McLauchlin, Jim, Aird, Heather, Amar, Corinne, Barker, Clare, Dallman, Timothy, Lai, Sandra, Painset, Anais, Willis, Caroline
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 02.01.2021; Elsevier BV
• Subjects: Beans; Corn; Disease Outbreaks; Distributors; England; Epidemiology; Food; Food and environmental surveillance; Food chains; Food Microbiology; Food production; Food safety; Foodborne Diseases - epidemiology; Foodborne Diseases - microbiology; Foodborne infection; Freezing; Frozen food; Frozen foods; Frozen products; Gene sequencing; Genomes; Humans; Listeria; Listeria monocytogenes; Listeria monocytogenes - genetics; Listeriosis; Listeriosis - epidemiology; Listeriosis - microbiology; Outbreaks; Sweet corn; Sweetcorn; United Kingdom; Vegetables; Vegetables - microbiology; Whole Genome Sequencing; Zea mays - microbiology; England; United Kingdom; United Kingdom > UK; Listeria monocytogenes; Food safety; Foodborne infection; Whole genome sequencing; Food and environmental surveillance; Sweet corn
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2020.108994

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. •A multi-country listeriosis outbreak was associated with Hungarian sweet corn.•12 cases were detected in the UK between 2015 and 2018.•Contaminated sweet corn was recovered from the freezer of a further case in 2019.•At the importer, 44% of sweet corn were contaminated, 6 strains were recovered.•A second possible sweet corn outbreak of two cases was detected.