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. 2022 Oct;27(41):2200316.
doi: 10.2807/1560-7917.ES.2022.27.41.2200316.

Salmonella Typhimurium outbreak associated with frozen tomato cubes at a restaurant in western Finland, January to February 2021

Sohvi Kääriäinen  1   2 , Dorothée Obach  1   2 , Dafni Katerina Paspaliari  1   3 , Marjut Tofferi  4 , Arto Nieminen  5 , Annika Pihlajasaari  6 , Henry Kuronen  7 , Anni Vainio  1 , Ruska Rimhanen-Finne  1
Affiliations

Salmonella Typhimurium outbreak associated with frozen tomato cubes at a restaurant in western Finland, January to February 2021

Sohvi Kääriäinen et al. Euro Surveill. 2022 Oct.

Abstract

Several individuals reported gastrointestinal symptoms following meals consumed in late January 2021 at a restaurant in western Finland. We conducted a retrospective cohort study and defined a case as a person who ate at the lunch restaurant between 27 and 29 January 2021 and had stomach pain, vomiting or diarrhoea and/or a laboratory-confirmed Salmonella Typhimurium infection within 2 weeks after the exposure. We collected faecal and food samples for microbiological analysis. Salmonella isolates were characterised in detail using whole genome sequencing (WGS) and cluster analysis by core genome multilocus sequence typing (cgMLST). Altogether, 393 meals were sold and 101 people (who ate 142 meals) participated in the cohort study. There were 49 cases; 23 were laboratory-confirmed infections with a multidrug-resistant S. Typhimurium. The S. Typhimurium isolates from cases and frozen tomato cubes used uncooked in salads were closely related and clustered together in cgMLST comparison. These salads were consumed by 76% of the cases. Based on the cgMLST clustering, they were the suggested source of the outbreak. Statistical association was not significant between eating the salads and being a case. Following the outbreak investigation, the producer decided to recommend cooking of their frozen tomato products before consumption.

Keywords: Salmonella Typhimurium; cohort study; multi-drug resistance; outbreak; tomato; whole genome sequencing.

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Conflict of interest statement

Conflict of interest: None declared.

Figures

Figure 1
Figure 1
Cases by date of symptom onset, Salmonella Typhimurium outbreak, western Finland, January–February 2021 (n = 47)
Figure 2
Figure 2
Number of cases and non-cases by date of the exposure, Salmonella Typhimurium outbreak, western Finland, January–February 2021 (n =101)
See this image and copyright information in PMC

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