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Strachan NJC, Hunter CJ, Jones CDR, Wilson RS, Ethelberg S, Cross P, Williams AP, MacRitchie L, Rotariu O, Chadwick D. The relationship between lay and technical views of Escherichia coli O157 risk. Philos Trans R Soc Lond B Biol Sci 2011; 366:1999-2009. [PMID: 21624920 DOI: 10.1098/rstb.2010.0393] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Here, we bring together and contrast lay (accessible primarily through social science methodologies) and technical (via risk assessment and epidemiological techniques) views of the risk associated with the Escherichia coli O157 pathogen using two case study areas in the Grampian region of Scotland, and North Wales. Epidemiological risk factors of contact with farm animals, visiting farms or farm fields and having a private water supply were associated with postcode districts of higher than average disease incidence in the human population. However, this was not the case for the epidemiological risk factor of consumption of beef burgers, which was independent of disease incidence in the postcode district of residence. The proportion of the population expressing a high knowledge of E. coli O157 was greatest in high-incidence disease districts compared with low-incidence areas (17% cf. 7%). This supports the hypothesis that in high-disease-incidence areas, residents are regularly exposed to information about the disease through local cases, the media, local social networks, etc. or perhaps that individuals are more likely to be motivated to find out about it. However, no statistically significant difference was found between high- and low-incidence postcode districts in terms of the proportion of the population expressing a high likelihood of personal risk of infection (10% cf. 14%), giving a counterintuitive difference between the technical (epidemiological and quantitative microbiological risk assessment (QMRA)) and the lay assessment of E. coli O157 risk. This suggests that lay evaluations of E. coli O157 risk reflect intuitive and experience-based estimates of the risk rather than probabilistic estimates. A generally strong correspondence was found in terms of the rank order given to potential infection pathways, with environment and foodborne infection routes dominating when comparing public understanding with technical modelling results. Two general conclusions follow from the work. First, that integrative research incorporating both lay and technical views of risk is required in order that informed decisions can be made to handle or treat the risk by the groups concerned (e.g. the public, policy makers/risk managers, etc.). Second, when communicating risk, for example, through education programmes, it is important that this process is two-way with risk managers (e.g. including Food Standards Agency officials and communications team, public health infection control and environmental health officers) both sharing information with the public and stakeholder groups, as well as incorporating public knowledge, values and context (e.g. geographical location) into risk-management decisions.
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Affiliation(s)
- N J C Strachan
- Department of Physics, SUPA, Institute of Biological and Environmental Sciences, School of Biological Sciences, Cruickshank Building, Saint Machar Drive, Aberdeen AB24 3UU, UK.
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Williams AP, Gordon H, Jones DL, Strachan NJC, Avery LM, Killham K. Leaching of bioluminescent Escherichia coli O157:H7 from sheep and cattle faeces during simulated rainstorm events. J Appl Microbiol 2010; 105:1452-60. [PMID: 19146485 DOI: 10.1111/j.1365-2672.2008.03898.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS Development of a novel inoculation technique to improve the current methods of determining the leaching of Escherichia coli O157:H7 from faeces. METHODS AND RESULTS Ruminant faeces were inoculated with a high [c. 10(7) colony forming units (CFU) g(-1)] or low (c. 10(4) CFU g(-1)) load of a lux-marked strain of E. coli O157:H7 via injection, and subjected to four simulated heavy rainfall events. The population density and metabolic activity of E. coli O157:H7 recovered within the leachate was determined following each simulated rain event and compared with the indigenous E. coli population. The concentration of E. coli O157:H7 in the leachates followed a similar trend to that of nonpathogenic E. coli. Significantly greater densities of generic and pathogenic E. coli were recovered in the leachates generated from sheep faeces compared with cattle faeces. Pathogen metabolic activity was also significantly greater in sheep faeces. CONCLUSIONS Our findings show that E. coli O157:H7 may readily leach from ruminant faeces during rain events. The bacterium leaches more freely from sheep faeces than from cattle faeces and displays greater metabolic activity within sheep leachate. SIGNIFICANCE AND IMPACT OF THE STUDY A novel inoculation technique was developed that allowed the determination of both population density and cellular activity of E. coli O157:H7 in leachate derived from faeces.
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Affiliation(s)
- A P Williams
- School of the Environment and Natural Resources, College of Natural Sciences, Bangor University, Gwynedd, UK
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Urdahl AM, Strachan NJC, Wasteson Y, Macrae M, Ogden ID. Diversity of Escherichia coli O157 in a longitudinal farm study using multiple-locus variable-number tandem-repeat analysis. J Appl Microbiol 2008; 105:1344-53. [PMID: 18631199 DOI: 10.1111/j.1365-2672.2008.03856.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS To perform a longitudinal study of the diversity of Escherichia coli O157 from a ruminant pasture/stream environment using multiple-locus variable-number tandem-repeat analysis (MLVA). METHODS AND RESULTS Samples of faecal droppings from grazing ruminants and from an adjacent stream were tested longitudinally for E. coli O157 by enrichment and immunomagnetic separation (IMS). Using MLVA, 24 different profiles were identified from a total of 231 E. coli O157 isolates, of which 80 were included in a similarity analysis. Four main clusters with several subclusters were observed. Although there was close contact between sheep and cattle during the study period, E. coli O157 was surprisingly not detected from cattle faeces. CONCLUSIONS The cluster analysis indicated both unrelated and closely related E. coli O157 strains. The choice of loci to target in MLVA is important for the subtyping result, as loci with high diversities are essential for discriminating between closely related isolates. SIGNIFICANCE AND IMPACT OF THE STUDY There is a lack of data available on the use of MLVA to describe E. coli O157 diversity and changes over time in the animal reservoirs and the environment. Such data are needed in order to further develop MLVA as a typing method.
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Affiliation(s)
- A M Urdahl
- Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Oslo, Norway.
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Teunis PFM, Ogden ID, Strachan NJC. Hierarchical dose response of E. coli O157:H7 from human outbreaks incorporating heterogeneity in exposure. Epidemiol Infect 2007; 136:761-70. [PMID: 17672927 PMCID: PMC2870861 DOI: 10.1017/s0950268807008771] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The infectivity of pathogenic microorganisms is a key factor in the transmission of an infectious disease in a susceptible population. Microbial infectivity is generally estimated from dose-response studies in human volunteers. This can only be done with mildly pathogenic organisms. Here a hierarchical Beta-Poisson dose-response model is developed utilizing data from human outbreaks. On the lowest level each outbreak is modelled separately and these are then combined at a second level to produce a group dose-response relation. The distribution of foodborne pathogens often shows strong heterogeneity and this is incorporated by introducing an additional parameter to the dose-response model, accounting for the degree of overdispersion relative to Poisson distribution. It was found that heterogeneity considerably influences the shape of the dose-response relationship and increases uncertainty in predicted risk. This uncertainty is greater than previously reported surrogate and outbreak models using a single level of analysis. Monte Carlo parameter samples (alpha, beta of the Beta-Poisson model) can be readily incorporated in risk assessment models built using tools such as S-plus and @ Risk.
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Affiliation(s)
- P F M Teunis
- National Institute of Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, Bilthoven, The Netherlands.
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Ogden ID, MacRae M, Johnston M, Strachan NJC, Cody AJ, Dingle KE, Newell DG. Use of multilocus sequence typing to investigate the association between the presence of Campylobacter spp. in broiler drinking water and Campylobacter colonization in broilers. Appl Environ Microbiol 2007; 73:5125-9. [PMID: 17586665 PMCID: PMC1950966 DOI: 10.1128/aem.00884-07] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The presence of campylobacters in broiler chickens and throughout the broiler water delivery systems of 12 farms in northeastern Scotland was investigated by sensitive enrichment methods and large-volume filtration. Campylobacter presence was independent of the water source and whether the water was treated. The genotypes of Campylobacter jejuni isolates recovered from chickens and various locations within the water delivery systems were compared by multilocus sequence typing. Matching strains in shed header tanks and birds were found at 1 of the 12 farms investigated. However, the sequence of contamination or whether the source was within or outside the shed was not determined. Nevertheless, these data provide evidence that drinking water could be associated with broiler infection by campylobacters.
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Affiliation(s)
- I D Ogden
- Department of Medical Microbiology, School of Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom.
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Abstract
AIMS To study the presence, numbers and virulence profiles of Escherichia coli O157 in sheep faeces and validate the microbiological methods used to attain these data. METHODS AND RESULTS Flock level prevalence was found to be 40% (six from 15) and 6.5% of faecal samples tested were found to be positive. Two farms gave samples defined as high shedding (>10(4) CFU g(-1)), one of which comprised 91% positive samples with 13/33 at the high shedding level. CONCLUSIONS These data confirmed that sheep are an important reservoir of E. coli O157. SIGNIFICANCE AND IMPACT OF THE STUDY Sheep play a significant role in the maintenance and dispersal of E. coli O157 in the farming environment and are an important source of human infection.
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Affiliation(s)
- I D Ogden
- Department of Medical Microbiology, School of Medicine, University of Aberdeen, Aberdeen, UK
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Affiliation(s)
- N J C Strachan
- School of Biological Sciences, University of Aberdeen, Cruickshank Building, St Machar Drive, Aberdeen AB24 3UU
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Rotariu O, Strachan NJC, Bădescu V. A stochastic model simulating the capture of pathogenic micro-organisms by superparamagnetic particles in an isodynamic magnetic field. Phys Med Biol 2004; 49:3971-8. [PMID: 15470917 DOI: 10.1088/0031-9155/49/17/010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The method of immunomagnetic separation (IMS) has become an established technique to concentrate and separate animal cells, biologically active compounds and pathogenic micro-organisms from clinical, food and environmental matrices. One drawback of this technique is that the analysis is only possible for small sample volumes. We have developed a stochastic model that involves numerical simulations to optimize the process of concentration of pathogenic micro-organisms onto superparamagnetic carrier particles (SCPs) in a gradient magnetic field. Within the range of the system parameters varied in the simulations, optimal conditions favour larger particles with higher magnetite concentrations. The dependence on magnetic field intensity and gradient together with concentration of particles and micro-organisms was found to be less important for larger SCPs but these parameters can influence the values of the collision time for small particles. These results will be useful in aiding the design of apparatus for immunomagnetic separation from large volume samples.
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Affiliation(s)
- O Rotariu
- School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, AB24 3UU UK.
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Miller G, Dunn GM, Smith-Palmer A, Ogden ID, Strachan NJC. Human campylobacteriosis in Scotland: seasonality, regional trends and bursts of infection. Epidemiol Infect 2004; 132:585-93. [PMID: 15310159 PMCID: PMC2870138 DOI: 10.1017/s0950268804002572] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fourier time-series models were constructed to study regional and national seasonality of human campylobacteriosis in Scotland between 1997 and 2001. Strong seasonality was demonstrated with an annual peak of reported cases in late June to early July. The prominence of this peak varied between regions, which was exemplified for the two major population centres: Lothian, with mixed urban/rural population, had a more prominent peak than Greater Glasgow, which has a predominantly urban population. No significant trend of annual cases of campylobacteriosis was found nationally and Fourier models successfully predicted the seasonal pattern of national and regional cases in 2002. During the period studied, the Fourier model identified >20 bursts of infection (potential outbreaks). Multi-regional bursts were also identified in the summers of 1998 and 2000 - the latter comprising the vast majority of the regions in Scotland, which could suggest a national outbreak.
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Affiliation(s)
- G Miller
- School of Biological Sciences, University of Aberdeen, Cruickshank Building, Aberdeen, Scotland, UK.
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Abstract
AIMS To compare immunomagnetic separation (IMS) protocols (enrichment media and temperature) for the isolation of Escherichia coli serotypes O26 and O111 from four different foods. METHODS AND RESULTS Foods (minced beef, cheese, apple juice and pepperoni) spiked with low numbers (<100 g(-1)) of stressed nalidixic mutant E. coli serotypes O26 and O111 were enriched in media based on buffered peptone water (BPW), tryptone soya and EC broths incubated at temperatures of 37 and 42 degrees C to optimize the IMS technique. BPW enrichments gave increased recoveries of both serotypes compared with tryptone soya and EC broths. Elevated temperatures of incubation at 42 degrees C were superior to 37 degrees C. CONCLUSIONS Positive detection of low numbers of stressed target pathogens in all replicate tests was only possible using BPW enrichments. The majority of tests from alternative enrichments resulted in zero or single colonies recovered post-IMS. SIGNIFICANCE AND IMPACT OF THE STUDY The optimum IMS protocol would improve isolation rates of E. coli O26 and O111 from foods and lead to increased safety for the consumer. Sub-optimal IMS protocols could lead to foods being incorrectly labelled free from these pathogens.
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Affiliation(s)
- M Drysdale
- Department of Medical Microbiology, Grampian University Hospital Trust, Aberdeen, UK
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Iacob G, Rotariu O, Strachan NJC, Häfeli UO. Magnetizable needles and wires--modeling an efficient way to target magnetic microspheres in vivo. Biorheology 2004; 41:599-612. [PMID: 15477667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
The in vivo targeting of tumors with magnetic microspheres is currently realized through the application of external non-uniform magnetic fields generated by rare-earth permanent magnets or electromagnets. Our theoretical work suggests a feasible procedure for local delivery of magnetic nano- and microparticles to a target area. In particular, thin magnetizable wires placed throughout or close to the target area and magnetized by a perpendicular external uniform background magnetic field are used to concentrate magnetic microspheres injected into the target organ's natural blood supply. The capture of the magnetic particles and the building of deposits thereof in the blood vessels of the target area were modeled under circumstances similar to the in vivo situation. This technique could be applied to magnetically targeted cancer therapy or magnetic embolization therapy with magnetic particles that contain anticancer agents, such as chemotherapeutic drugs or therapeutic radioisotopes.
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Affiliation(s)
- Gh Iacob
- University of Medicine and Pharmacy, Faculty of Medical Bioengineering, Iasi, Romania
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Omisakin F, MacRae M, Ogden ID, Strachan NJC. Concentration and prevalence of Escherichia coli O157 in cattle feces at slaughter. Appl Environ Microbiol 2003; 69:2444-7. [PMID: 12732509 PMCID: PMC154535 DOI: 10.1128/aem.69.5.2444-2447.2003] [Citation(s) in RCA: 218] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2002] [Accepted: 02/07/2003] [Indexed: 11/20/2022] Open
Abstract
The concentration and prevalence of Escherichia coli O157 in cattle feces at the time of slaughter was studied over a 9-week period from May to July 2002. Fecal samples (n = 589) were collected from the rectums of slaughtered cattle, and the animal-level prevalence rate was estimated to be 7.5% (95% confidence interval [CI], 5.4 to 9.6%) while the group prevalence was 40.4% (95% CI, 27.7 to 53.2%). Of the 44 infected animals detected, 9% were high shedders that contained E. coli O157 at concentrations of >10(4) CFU g(-1). These 9% represented >96% of the total E. coli O157 produced by all animals tested. All isolates possessed the vt(2) gene, 39 had the eaeA gene, and a further five had the vt(1) gene also. The presence of high-shedding animals at the abattoir increases the potential risk of meat contamination during the slaughtering process and stresses the need for correctly implemented hazard analysis and critical control point procedures.
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Affiliation(s)
- F Omisakin
- School of Biological Sciences, Department of Medical Microbiology, University of Aberdeen, Aberdeen AB24 3UU, Scotland, United Kingdom
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Ogden ID, Hepburn NF, MacRae M, Strachan NJC, Fenlon DR, Rusbridge SM, Pennington TH. Long-term survival of Escherichia coli O157 on pasture following an outbreak associated with sheep at a scout camp. Lett Appl Microbiol 2002; 34:100-4. [PMID: 11849503 DOI: 10.1046/j.1472-765x.2002.01052.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIMS To monitor the decay of E. coli O157 in soil (loamy sand) on a scout campsite following an outbreak in humans. METHODS AND RESULTS Samples of soil and sheep faeces were collected from the campsite and tested for the presence of E. coli O157 by immunomagnetic separation (IMS) after enrichment in buffered peptone water + vancomycin at 42 degrees C for 6 h. Enumeration of target was carried out by direct plating onto sorbitol MacConkey agar plates supplemented with cefixime and tellurite (CTSMAC) incubated at 37 degrees C for 24 h. Low numbers (< 100 g(-1)) were estimated by the most probable number (3-tube MPN) technique. CONCLUSIONS Survival was observed for 15 weeks. SIGNIFICANCE AND IMPACT OF THE STUDY A number of laboratory studies have followed the decay of E. coli O157 in soil, animal faeces and water. This study follows (for the first time) the decay of the organism in soil after an outbreak associated with sheep. It demonstrates the long-term persistence of the organism in the environment and the results will be potentially important in performing risk assessments for both human and animal infection.
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Affiliation(s)
- I D Ogden
- Department of Medical Microbiology, University of Aberdeen, Foresterhill, Aberdeen, UK.
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Strachan NJC, John PG, Millar IG. Application of an automated particle‐based immunosensor for the detection of aflatoxin B1in foods. FOOD AGR IMMUNOL 1997. [DOI: 10.1080/09540109709354948] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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