Surveillance and outbreak report Open Access
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There is a need for innovative methods to investigate outbreaks of food-borne infection linked to produce with a complex distribution network. The investigation of a large outbreak of O157 PT34 infection in the United Kingdom in 2016 indicated that catering venues associated with multiple cases had used salad leaves sourced from one supplier. Our aim was to investigate whether catering venues linked to cases were more likely to have used salad leaves from this supplier. We conducted a matched case–control study, with catering venues as the units of analysis. We compared venues linked to cases to those without known linked cases. We included 43 study pairs and obtained information on salad leaf products received by each venue. The odds of a case venue being supplied with salad leaves by Supplier A were 7.67 times (95% confidence interval: 2.30–25.53) those of control venues. This association provided statistical evidence to support the findings of the other epidemiological investigations undertaken for this outbreak. This is a novel approach which is labour-intensive but which addresses the challenge of investigating exposures to food across a complex distribution network.


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  1. Tarr PI, Gordon CA, Chandler WL. Shiga-toxin-producing Escherichia coli and haemolytic uraemic syndrome. Lancet. 2005;365(9464):1073-86. PMID: 15781103 
  2. Adams NL, Byrne L, Smith GA, Elson R, Harris JP, Salmon R, et al. Shiga toxin-producing Escherichia coli O157, England and Wales, 1983-2012. Emerg Infect Dis. 2016;22(4):590-7.  https://doi.org/10.3201/eid2204.151485  PMID: 26982243 
  3. Ihekweazu C, Carroll K, Adak B, Smith G, Pritchard GC, Gillespie IA, et al. Large outbreak of verocytotoxin-producing Escherichia coli O157 infection in visitors to a petting farm in South East England, 2009. Epidemiol Infect. 2012;140(8):1400-13.  https://doi.org/10.1017/S0950268811002111  PMID: 22093751 
  4. Launders N, Locking ME, Hanson M, Willshaw G, Charlett A, Salmon R, et al. A large Great Britain-wide outbreak of STEC O157 phage type 8 linked to handling of raw leeks and potatoes. Epidemiol Infect. 2016;144(1):171-81.  https://doi.org/10.1017/S0950268815001016  PMID: 26041509 
  5. Michino H, Araki K, Minami S, Takaya S, Sakai N, Miyazaki M, et al. Massive outbreak of Escherichia coli O157:H7 infection in schoolchildren in Sakai City, Japan, associated with consumption of white radish sprouts. Am J Epidemiol. 1999;150(8):787-96.  https://doi.org/10.1093/oxfordjournals.aje.a010082  PMID: 10522649 
  6. Söderström A, Österberg P, Lindqvist A, Jönsson B, Lindberg A, Blide Ulander S, et al. A large Escherichia coli O157 outbreak in Sweden associated with locally produced lettuce. Foodborne Pathog Dis. 2008;5(3):339-49.  https://doi.org/10.1089/fpd.2007.0065  PMID: 18767979 
  7. Bell BP, Goldoft M, Griffin PM, Davis MA, Gordon DC, Tarr PI, et al. A multistate outbreak of Escherichia coli O157:H7-associated bloody diarrhea and hemolytic uremic syndrome from hamburgers. The Washington experience. JAMA. 1994;272(17):1349-53.  https://doi.org/10.1001/jama.1994.03520170059036  PMID: 7933395 
  8. Miller BD, Rigdon CE, Ball J, Rounds JM, Klos RF, Brennan BM, et al. Use of traceback methods to confirm the source of a multistate Escherichia coli O157:H7 outbreak due to in-shell hazelnuts. J Food Prot. 2012;75(2):320-7.  https://doi.org/10.4315/0362-028X.JFP-11-309  PMID: 22289593 
  9. Jay MT, Garrett V, Mohle-Boetani JC, Barros M, Farrar JA, Rios R, et al. A multistate outbreak of Escherichia coli O157:H7 infection linked to consumption of beef tacos at a fast-food restaurant chain. Clin Infect Dis. 2004;39(1):1-7.  https://doi.org/10.1086/421088  PMID: 15206044 
  10. Sodha SV, Lynch M, Wannemuehler K, Leeper M, Malavet M, Schaffzin J, et al. Multistate outbreak of Escherichia coli O157:H7 infections associated with a national fast-food chain, 2006: a study incorporating epidemiological and food source traceback results. Epidemiol Infect. 2011;139(2):309-16.  https://doi.org/10.1017/S0950268810000920  PMID: 20429971 
  11. Gobin M, Hawker J, Cleary P, Inns T, Gardiner D, Mikhail A, et al. National outbreak of Shiga toxin-producing Escherichia coli O157:H7 linked to mixed salad leaves, United Kingdom, 2016. Euro Surveill. 2017;23(18):17-00197.
  12. Weiser AA, Thöns C, Filter M, Falenski A, Appel B, Käsbohrer A. FoodChain-Lab: a trace-back and trace-forward tool developed and applied during food-borne disease outbreak investigations in Germany and Europe. PLoS One. 2016;11(3):e0151977.  https://doi.org/10.1371/journal.pone.0151977  PMID: 26985673 
  13. Ackers M-L, Mahon BE, Leahy E, Goode B, Damrow T, Hayes PS, et al. An outbreak of Escherichia coli O157:H7 infections associated with leaf lettuce consumption. J Infect Dis. 1998;177(6):1588-93.  https://doi.org/10.1086/515323  PMID: 9607837 
  14. Buchholz U, Bernard H, Werber D, Böhmer MM, Remschmidt C, Wilking H, et al. German outbreak of Escherichia coli O104:H4 associated with sprouts. N Engl J Med. 2011;365(19):1763-70.  https://doi.org/10.1056/NEJMoa1106482  PMID: 22029753 
  15. Sinclair C, Jenkins C, Warburton F, Adak GK, Harris JP. Investigation of a national outbreak of STEC Escherichia coli O157 using online consumer panel control methods: Great Britain, October 2014. Epidemiol Infect. 2017;145(5):864-71.  https://doi.org/10.1017/S0950268816003009  PMID: 27964764 
  16. Dallman T, Inns T, Jombart T, Ashton P, Loman N, Chatt C, et al. Phylogenetic structure of European Salmonella Enteritidis outbreak correlates with national and international egg distribution network. Microb Genom. 2016;2(8):e000070.  https://doi.org/10.1099/mgen.0.000070  PMID: 28348865 
  17. Regulation (EC) No 178/2002 of the European Parliament and of the Council of 28 January 2002 laying down the general principles and requirements of food law, establishing the European Food Safety Authority and laying down procedures in matters of food safety. Official Journal of the European Communities. 2002. L 31/1. Available from: http://eur-lex.europa.eu/eli/reg/2002/178/oj

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