REDUCING ESCHERICHIA COLI O157 RISK IN RURAL COMMUNITIES

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REDUCING ESCHERICHIA COLI O157 RISK IN RURAL
COMMUNITIES Ken Killham, Gareth Edwards-Jones,
Jenny Roberts, Ada Wossink, Colin Hunter, Dave
Chadwick, Iain Ogden, Davey Jones, Norval
Strachan, Dan Rigby, John Farringdon, Peter
Teunis and Rowena Kosmider

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E.coli O157- a rural issue
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Meet the culprit- E. coli O157

• Gram negative rod shaped bacterium
• Facultative anaerobe
• Produces verocytotoxin encoded by vt1 and vt2
  genes
• Flagella are encoded by the H7 antigen

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The scale of the problem
E. coli O157H7 can reside in the gut of cattle
without any observable effect 1 - 4 of UK
cattle herd infected with E. coli O157H7 High
as 16 in certain localities Faecal excretion
rates typically range from 102 - 105 cfus g-1
faeces As little as 100 ?g faeces required for
infection
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Pathways for human E. coli O157 infection
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Key epidemiological and biological questions
remain unanswered in terms of O157 as a rural
issue

• Why do agricultural workers appear to be less
  susceptible
• to infection than urban populations?
• Do they develop immunity to pathogens as a result
  of low level
• prolonged exposure?
• Although E. coli O157 can persist outside the
  host in a metabolically inactive state (e.g. in
  soil and water), does it still remain infective
  to humans and animals?
• What factors within agricultural environments
  pose the greatest risk to human and animal
  (re)infection?

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How is E. coli O157 risk
currently perceived, communicated and managed
amongst stakeholder groups?What is the actual
cost to the UK economy of E. coli O157, and what
intervention measures will most cost effectively
manage pathogen risk in UK rural
environments?What intervention methods will
provide the most socially acceptable management
regime?
Key socioeconomic questions underpin these issues
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Key expertise- detection of E. coli O157H7 in
environmental samples

• Culture based detection methods
• Vero cell culture assay
• Immunochemical methods
• PCR based methods
• Marker/reporter gene methods

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PCR detection of populations of E. coli O157 in
soil- sensitivity as low as 3 cells g-1

• Primers included in assay to target O157, H7,
  intimin and shiga toxin I and II encoding genes

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PCR detection sensitivity in different
environmental matrices
Environmental material
PCR detection sensitivity
Glencorse agricultural soil
3 cfu g-1 oven dry soil
Cruden Bay agricultural soil
10 cfu g-1 oven dry soil
River Don water
8 cfu ml-1
River Dee water
6 cfu ml-1
Private drinking water
1 cfu ml-1
Numbers represent initial cfu added to sample
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Contaminant biosensors and bioremediation

• Rhizobium

• (Metabolic and catabolic sensors)

FMNH2 O2 Aldehyde luciferase FMN fatty acid
LIGHT
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Soil leaching studies involving a lux-marked
construct of E. coli O157H7 - different soil
types
E. coli O157H7 inoculum (lux marked)
artificial rainfall
re-packed soil leaching column
leachate
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In situ tracking of marked pathogens
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Referencing the soils database is enabling
catchment management of O157 fate

• Data on survival and dispersal through soils is
  being coupled to soil and environmental GIS for
  catchment management

Interactive Soils E. A. Fitzpatrick, University
of Aberdeen
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E.coli O157 and risk assessment

• A number of outbreaks and sporadic cases
  attributed to environmental contact
• Risk Assessment Model (Strachan et al, 2002)
• Compare approximate beta-Poisson model with
  Shigella Model and EPEC Model

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A truly multidisciplinary approach
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Objectives of Research

• The key objectives of this multidisciplinary
  project are
• Discover how stakeholder groups perceive O157
  risk.
• 2. Ascertain and evaluate the persistence and
  asymptomatic carriage of O157.
• 3. Ascertain how O157 maintains environmental
  infectivity.
• 4. Formulate intervention and mitigation
  strategies to better manage O157 risk.
• 5. Assess cost/social acceptability of risk
  management strategies.
• 6. Produce risk management strategies for
  integration into government policy.

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• An integrated, multidisciplinary work programme

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Deliverables1) Using integrated quantitative
and qualitative data-gathering, understand the
knowledge-forming, attitudinal, and behavioural
processes in key stakeholders to formulate a
policy-relevant intervention strategy2) Provide
critical data on persistence, transmission and
infectivity of E. coli O157 in the rural
environment for predictive modelling across the
agroclimatic and edaphic ranges of the UK.3)
Construct reliable risk assessment models and
maps, incorporating socioeconomic and scientific
evidence to underpin policy intervention and
management options for minimisation of O157
transfer of to rural stakeholders/ communities.
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REDUCING ESCHERICHIA COLI O157 RISK IN RURAL
COMMUNITIES Contact Ken Killham
(k.killham_at_abdn.ac.uk)