An outbreak of Shiga toxin-producing Escherichia coli O157:H7 associated with contaminated salad leaves: Epidemiological, genomic and food trace back investigations

A. F.W. Mikhail; Claire Jenkins; Tim Dallman; Thomas Inns; A. I.C. Martín; A. Fox; Paul Cleary; Richard Elson; Jeremy Hawker

doi:10.1017/S0950268817002874

An outbreak of Shiga toxin-producing Escherichia coli O157:H7 associated with contaminated salad leaves: Epidemiological, genomic and food trace back investigations

A. F.W. Mikhail, Claire Jenkins^*, Tim Dallman, Thomas Inns, A. I.C. Martín, A. Fox, Paul Cleary, Richard Elson, Jeremy Hawker

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

56 Citations (Scopus)

Abstract

In August 2015, Public Health England detected an outbreak of Shiga toxin-producing Escherichia coli (STEC) serotype O157:H7 caused by contaminated salad leaves in a mixed leaf prepacked salad product from a national retailer. The implicated leaves were cultivated at five different farms and the zoonotic source of the outbreak strain was not determined. In March 2016, additional isolates from new cases were identified that shared a recent common ancestor with the outbreak strain. A case-case study involving the cases identified in 2016 revealed that ovine exposures were associated with illness (n = 16; AOR 8·24; 95% CI 1·55-39·74). By mapping the recent movement of sheep and lambs across the United Kingdom, epidemiological links were established between the cases reporting ovine exposures. Given the close phylogenetic relationship between the outbreak strain and the isolates from cases with ovine exposures, it is plausible that ovine faeces may have contaminated the salad leaves via untreated irrigation water or run-off from fields nearby. Timely and targeted veterinary and environmental sampling should be considered during foodborne outbreaks of STEC, particularly where ready to eat vegetables and salads are implicated.

Original language	English
Pages (from-to)	187-196
Number of pages	10
Journal	Epidemiology and Infection
Volume	146
Issue number	2
DOIs	https://doi.org/10.1017/S0950268817002874
Publication status	Published - 1 Jan 2018

Bibliographical note

Funding Information:
The authors would like to thank Neil Perry, Vivienne do Nascimento and Marie Chattaway at GBRU, Kate James from PHE WM Centre and colleagues at PHE Food, Water and Environmental Microbiology Laboratories and Preston, Porton and Birmingham. The authors would also like to acknowledge everyone who was part of the Outbreak Control Team including Drazenka Tubin-Delic, Jonathan Lighthill and Joanne Edge the Food Standards Agency, Paul Homes, Alan Wright and Charlotte Featherstone at the Animal and Plant Health Agency and Eamon Rodgers at Worcestershire Regulatory Services County Council. This work was supported by the National Institute for Health Research Health Protection Research Unit in Gastrointestinal Infections. Jeremy Hawker, Richard Elson, Paul Cleary, Tim Dallman and Tom Inns are affiliated to the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Gastrointestinal Infections at University of Liverpool in partnership with PHE, in collaboration with University of East Anglia, University of Oxford and the Institute of Food Research. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, the Department of Health or PHE.

Publisher Copyright:
© 2017 Cambridge University Press .

Keywords

Bacterial typing
Shiga-like toxin-producing E. coli
epidemiology
public health microbiology
zoonotic foodborne diseases

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1017/S0950268817002874

Cite this

Mikhail, A. F. W., Jenkins, C., Dallman, T., Inns, T., Martín, A. I. C., Fox, A., Cleary, P., Elson, R., & Hawker, J. (2018). An outbreak of Shiga toxin-producing Escherichia coli O157:H7 associated with contaminated salad leaves: Epidemiological, genomic and food trace back investigations. Epidemiology and Infection, 146(2), 187-196. https://doi.org/10.1017/S0950268817002874

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abstract = "In August 2015, Public Health England detected an outbreak of Shiga toxin-producing Escherichia coli (STEC) serotype O157:H7 caused by contaminated salad leaves in a mixed leaf prepacked salad product from a national retailer. The implicated leaves were cultivated at five different farms and the zoonotic source of the outbreak strain was not determined. In March 2016, additional isolates from new cases were identified that shared a recent common ancestor with the outbreak strain. A case-case study involving the cases identified in 2016 revealed that ovine exposures were associated with illness (n = 16; AOR 8·24; 95% CI 1·55-39·74). By mapping the recent movement of sheep and lambs across the United Kingdom, epidemiological links were established between the cases reporting ovine exposures. Given the close phylogenetic relationship between the outbreak strain and the isolates from cases with ovine exposures, it is plausible that ovine faeces may have contaminated the salad leaves via untreated irrigation water or run-off from fields nearby. Timely and targeted veterinary and environmental sampling should be considered during foodborne outbreaks of STEC, particularly where ready to eat vegetables and salads are implicated.",

keywords = "Bacterial typing, Shiga-like toxin-producing E. coli, epidemiology, public health microbiology, zoonotic foodborne diseases",

author = "Mikhail, {A. F.W.} and Claire Jenkins and Tim Dallman and Thomas Inns and Mart{\'i}n, {A. I.C.} and A. Fox and Paul Cleary and Richard Elson and Jeremy Hawker",

note = "Funding Information: The authors would like to thank Neil Perry, Vivienne do Nascimento and Marie Chattaway at GBRU, Kate James from PHE WM Centre and colleagues at PHE Food, Water and Environmental Microbiology Laboratories and Preston, Porton and Birmingham. The authors would also like to acknowledge everyone who was part of the Outbreak Control Team including Drazenka Tubin-Delic, Jonathan Lighthill and Joanne Edge the Food Standards Agency, Paul Homes, Alan Wright and Charlotte Featherstone at the Animal and Plant Health Agency and Eamon Rodgers at Worcestershire Regulatory Services County Council. This work was supported by the National Institute for Health Research Health Protection Research Unit in Gastrointestinal Infections. Jeremy Hawker, Richard Elson, Paul Cleary, Tim Dallman and Tom Inns are affiliated to the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Gastrointestinal Infections at University of Liverpool in partnership with PHE, in collaboration with University of East Anglia, University of Oxford and the Institute of Food Research. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, the Department of Health or PHE. Publisher Copyright: {\textcopyright} 2017 Cambridge University Press .",

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Mikhail, AFW, Jenkins, C, Dallman, T, Inns, T, Martín, AIC, Fox, A , Cleary, P, Elson, R & Hawker, J 2018, 'An outbreak of Shiga toxin-producing Escherichia coli O157:H7 associated with contaminated salad leaves: Epidemiological, genomic and food trace back investigations', Epidemiology and Infection, vol. 146, no. 2, pp. 187-196. https://doi.org/10.1017/S0950268817002874

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AU - Cleary, Paul

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N2 - In August 2015, Public Health England detected an outbreak of Shiga toxin-producing Escherichia coli (STEC) serotype O157:H7 caused by contaminated salad leaves in a mixed leaf prepacked salad product from a national retailer. The implicated leaves were cultivated at five different farms and the zoonotic source of the outbreak strain was not determined. In March 2016, additional isolates from new cases were identified that shared a recent common ancestor with the outbreak strain. A case-case study involving the cases identified in 2016 revealed that ovine exposures were associated with illness (n = 16; AOR 8·24; 95% CI 1·55-39·74). By mapping the recent movement of sheep and lambs across the United Kingdom, epidemiological links were established between the cases reporting ovine exposures. Given the close phylogenetic relationship between the outbreak strain and the isolates from cases with ovine exposures, it is plausible that ovine faeces may have contaminated the salad leaves via untreated irrigation water or run-off from fields nearby. Timely and targeted veterinary and environmental sampling should be considered during foodborne outbreaks of STEC, particularly where ready to eat vegetables and salads are implicated.

AB - In August 2015, Public Health England detected an outbreak of Shiga toxin-producing Escherichia coli (STEC) serotype O157:H7 caused by contaminated salad leaves in a mixed leaf prepacked salad product from a national retailer. The implicated leaves were cultivated at five different farms and the zoonotic source of the outbreak strain was not determined. In March 2016, additional isolates from new cases were identified that shared a recent common ancestor with the outbreak strain. A case-case study involving the cases identified in 2016 revealed that ovine exposures were associated with illness (n = 16; AOR 8·24; 95% CI 1·55-39·74). By mapping the recent movement of sheep and lambs across the United Kingdom, epidemiological links were established between the cases reporting ovine exposures. Given the close phylogenetic relationship between the outbreak strain and the isolates from cases with ovine exposures, it is plausible that ovine faeces may have contaminated the salad leaves via untreated irrigation water or run-off from fields nearby. Timely and targeted veterinary and environmental sampling should be considered during foodborne outbreaks of STEC, particularly where ready to eat vegetables and salads are implicated.

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An outbreak of Shiga toxin-producing Escherichia coli O157:H7 associated with contaminated salad leaves: Epidemiological, genomic and food trace back investigations

Abstract

Bibliographical note

Keywords

UN SDGs

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