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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
E.coli O157- a rural issue
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
The scale of the problemE. coli O157:H7 can reside in the gut of cattle without any observable effect
1 - 4% of UK cattle herd infected with E. coli O157:H7
High as 16% in certain localities
Faecal excretion rates typically range from 102 - 105 cfu’s g-1 faeces
As little as 100 g faeces required for infection
Pathways for human E. coli O157 infection
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?
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
Key expertise- detection of E. coli O157:H7 in
environmental samples
• Culture based detection methods
• Vero cell culture assay• Immunochemical methods• PCR based methods• Marker/reporter gene methods
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
1g soil / 1 ml water added to 20 ml of TSB
2 ml primary enrichment culture added to 20 ml fresh TSB
15 hr
37oC
Centrifuge cells and extract DNA for PCR analysis
6 hr
37oC
PCR detection sensitivity in different environmental matrices
Environmental material
PCR detection sensitivity
Cruden Bay agricultural soil
Glencorse agricultural soil
River Don water
River Dee water
Private drinking water
3 cfu g-1 oven dry soil
6 cfu ml-1
10 cfu g-1 oven dry soil8 cfu ml-1
1 cfu ml-1
Numbers represent initial cfu added to sample
lux R lux I lux Dlux C lux E
COOHN COOHN
lux Blux A
Luciferase
O2Light
Contaminant biosensors and bioremediation
Pseudomonas
FMNH2 + O2 + Aldehydeluciferase FMN + fatty acid + LIGHT
•(Metabolic and catabolic sensors)
Rhizobium
Soil leaching studies involving a lux-marked construct of E. coli O157:H7 -
different soil types
leachate
re-packed soil leaching column
artificial rainfall
E. coli O157:H7 inoculum (lux marked)
0
1
2
3
4
5
6
7
8
0 - 5 30 - 45 60 - 75
Leaching period (min after inoculation)
Mea
n %
initia
l inocu
lum
Boyndie 3704 Boyndie 3704 pUCD607
Cruden Bay 3704 Cruden Bay 3704 pUCD607
Insch 3704 Insch 3704 pUCD607
In situ tracking of marked pathogens
Interactive Soils: E. A. Fitzpatrick, University of Aberdeen
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
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
A truly multidisciplinary approach
Objectives of Research
The key objectives of this multidisciplinary project are:1. 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.
Critical data on persistence, transmission, infectivity
Predictive modelling across agroclimatic and edaphic ranges
Risk Assessment maps and socio-economic models
Environ-mental
management and policy
change
Environmental and tourism NGAs-SNH, CCW, Natural England, Tourist
boards
Education-Education authorities, Schools
Communicators- Media (TV, newspapers, radio etc), opinion
formers
Consumers – Public
1. Evaluation of E. coli O157 carriage within rural communities
2. Linking E. coli O157 survival with infectivity
3. Risk assessment modelling & initial mitigation strategy
4. Economic costs of impacts and intervention
5. Testing initial risk management strategies: social and economic impacts
6. Evidence-based policy formulation and
dissemination
Regulators- DEFRA, SEERAD, EA, SEPA, DH, FSA, Local Authorities.
Land users- farmers, contractors,foresters, tourists, NFU, NUFL
Food industry- abattoirs, supermarkets, catering contractors, butchers, meat marketing, QMS.
Work Packages Key Deliverables
Communicators- Media (TV, newspapers, radio
etc), opinion formers
Integration
• An integrated, multidisciplinary work programme
Deliverables
1) Using integrated quantitative and qualitative data-gathering, understand the knowledge-forming, attitudinal,
and behavioural processes in key stakeholders to formulate a policy-relevant intervention strategy
2) 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.
