Risk Assessment Of Pathogens Research Articles

A Risk Assessment Framework for Waterborne Pathogens and Requirements for Producing a Complete Protocol

ABSTRACT The U.S. Environmental Protection Agency (USEPA), Office of Water, is developing a risk assessment protocol for determining microbiological pathogen risks in water (drinking, recreational, waste waters, etc.). This effort has been conducted in collaboration with the International Life Sciences Institute. A microbiological risk assessment framework was prepared and has been peer reviewed in the open literature and vetted at the USEPA and other federal government risk assessment venues. Some goals in development of the Framework were to make it comprehensive, easy to understand and to use, since it is recognized that improvements to the framework structure and instructional material would facilitate its use. The USEPA's Office of Water wishes to develop improved tools, methods, and approaches for conducting the analysis phase for risk assessments and would like to evaluate its efficacy for a broad range of waterborne pathogens in water/wastewater media. Improved understanding of microbiological survival, infectivity, and virulence factors is needed, especially at the genomic and proteomic levels to accurately assess the occurrence and fate of pathogens in water and to predict what intrinsic factors allow pathogens to be invasive and virulent. Development of improved dose-response models (including animal models) for pathogen exposures focusing on the dynamic circumstances of immunity, secondary spread, and sensitive subpopulations, would be useful additions to the Framework. In the future, USEPA may consider establishing comprehensive pathogen risk assessment guidelines that all its program offices can use.

Prioritizing watershed pathogen research

Water treatment professionals are generally aware of the issues regarding the fate and transport of pathogens within watersheds. However, not all water treatment professionals are in a scientific field nor do they all have the same level of knowledge of the range of international projects being conducted to address this issue. To counter a current lack of quantitative data on the biophysical and chemical parameters that drive pathogen survival and transport in watersheds, the authors created a conceptual model of a watershed that water suppliers can use as a starting point to create their own pathogen risk assessment and to prioritize their research to target identified knowledge gaps. These findings make it possible to identify the next steps for research and focus on the chemical, physical, and biological processes that underpin pathogen transport and attenuation while avoiding duplicative research efforts.

Verticillium wilt in tree species; elements for integrated and innovative management strategies (EU-Project QLRT-CT99-1523)

Verticillium wilt is of increasing significance in European agriculture, especially in tree hosts such as olive and stone fruits, and in shade tree nurseries. In the period 1997–1998 eight European research groups participated in an EU-funded Concerted Action on this disease. Main results were the publication of “A Compendium on Verticillium wilts in tree species” (HIEMSTRA & HARRIS 1998) and an RTD-proposal submitted for financing to the 5th EU Framework Programme. This proposal was approved by the European Commission and the research started in March 2000. Ten research groups participate in a project that aims to provide essential elements for an efficient and environmentally sound management of Verticillium wilt in trees. The research concentrates on tree key areas: (1) pathogen variability, (2) host resistance, and (3) detection and risk assessment. In addition the project aims at harmonising methods, exchange of experience and continuation of the successful co-operation developed during the previous Concerted Action. The specific achievements of the project include information on genetic variation within the pathogen and on distribution and virulence of its subspecific groups; standardised methods to select for host resistance; resistant selections of olive and maple; molecular methods to detect the pathogen in soil and plants; and improved risk assessment procedures. Details on aims, methods and participating groups will be presented.

Risk Assessment for Enteric Pathogens in the Biosafety Level 2 Laboratory

There is some general confusion regarding when to use a biological safety cabinet (BSC) to minimize risk from aerosol formation in Biosafety Level 2 (BSL'2) laboratories that handle enteric pathogens. A risk assessment was conducted to determine the risk involved in performing some standard microbiological manipulations. Although enteric organisms are not known to be infectious via inhalation, it was felt ingestion of droplets deposited around the work area may cause laboratory-acquired infection. Manipulations of Salmonella spp., Shigella spp., Escherichia coli 0157, and other E. coli have resulted in laboratory-acquired infection due to improper laboratory technique. Routine procedures, for example opening screw-capped bottles and wet petri dish covers, improper use of needle and septum, streaking plates, pipetting, slide agglutination, and microscopic preparations, were found to have potential to cause aerosol formation. Proper microbiological technique in combination with primary containment devices (e.g., biological safety cabinets) has been found to reduce the risk of laboratory-acquired infections when working with enteric pathogens. Laboratory workers must ensure that they use any means available to minimize these risks.

Introduction to special section on sensitivity analysis and summary of NCSU/USDA workshop on sensitivity analysis.

This guest editorial is a summary of the NCSU/USDA Workshop on Sensitivity Analysis held June 11-12, 2001 at North Carolina State University and sponsored by the U.S. Department of Agriculture's Office of Risk Assessment and Cost Benefit Analysis. The objective of the workshop was to learn across disciplines in identifying, evaluating, and recommending sensitivity analysis methods and practices for application to food-safety process risk models. The workshop included presentations regarding the Hazard Assessment and Critical Control Points (HACCP) framework used in food-safety risk assessment, a survey of sensitivity analysis methods, invited white papers on sensitivity analysis, and invited case studies regarding risk assessment of microbial pathogens in food. Based on the sharing of interdisciplinary information represented by the presentations, the workshop participants, divided into breakout sessions, responded to three trigger questions: What are the key criteria for sensitivity analysis methods applied to food-safety risk assessment? What sensitivity analysis methods are most promising for application to food safety and risk assessment? and What are the key needs for implementation and demonstration of such methods? The workshop produced agreement regarding key criteria for sensitivity analysis methods and the need to use two or more methods to try to obtain robust insights. Recommendations were made regarding a guideline document to assist practitioners in selecting, applying, interpreting, and reporting the results of sensitivity analysis.

INFECTIVE DOSE OF FOODBORNE PATHOGENS IN VOLUNTEERS: A REVIEW

ABSTRACT Risk assessment and impact of foodborne pathogens on the health of different populations was one of the goals identified in the Presidential Food Safety Initiative three‐year plan. This entailed estimation of dose‐response relationship for foodborne pathogens to humans, either by feeding studies or from outbreaks. For certain pathogens, such as Listeria monocytogenes and Escherichia coli O157:H7, there are no feeding studies due to ethical reasons, and the results from outbreaks are normally used to estimate the infectious dose. The focus of this review is to compile dose‐response information in volunteers for several foodborne pathogens including Salmonella, Shigella spp., Campylobacter jejuni, Vibrio spp., Escherichia coli, Cryptosporidium parvum and Entamoeba coli. The infectious dose for different serovars of Salmonella and strains of E. coli was quite large (> 105 organisms), while the infectious dose for some Shigella spp. seemed to be as low as less than 10 organisms. Toxigenic V. cholerae (O1 and O139 serotypes) were infective at a dose of 104 organisms; a non‐O1 strain was infective at a much higher dose (106 organisms). C. jejuni, C. parvum and Entamoeba coli appeared to have infectious doses as low as 500 organisms, 10 oocysts, and 1 cyst, respectively. The infectious dose and the dose response are dependent upon the strains used, and the age and physical condition of the individuals, and can therefore show wide variations. In addition, since many of the volunteer studies are carried out by feeding the organisms in a nonfood matrix after neutralizing the stomach acidity, results obtained may not reflect the true dose response.

Susceptibility in Microbial Risk Assessment: Definitions and Research Needs

Research ArticleOpen AccessSusceptibility in microbial risk assessment: definitions and research needs. J Balbus, R Parkin, and M Embrey J Balbus Center for Risk Science and Public Health, The George Washington University School of Public Health and Health Services, Washington, DC 20037, USA. Search for more papers by this author , R Parkin Center for Risk Science and Public Health, The George Washington University School of Public Health and Health Services, Washington, DC 20037, USA. Search for more papers by this author , and M Embrey Center for Risk Science and Public Health, The George Washington University School of Public Health and Health Services, Washington, DC 20037, USA. Search for more papers by this author Published:1 September 2000https://doi.org/10.1289/ehp.00108901Cited by:9AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit FiguresReferencesRelatedDetailsCited by Dunn M (2012) A Complaint from Citizens for Sludge-Free Land, NEW SOLUTIONS: A Journal of Environmental and Occupational Health Policy, 10.2190/NS.22.2.g, 22:2, (213-220), Online publication date: 1-Aug-2012. Balbus J, Parkin R, Makri A, Ragain L, Embrey M and Hauchman F (2004) Defining Susceptibility for Microbial Risk Assessment: Results of a Workshop, Risk Analysis, 10.1111/j.0272-4332.2004.00423.x, 24:1, (197-208), Online publication date: 1-Feb-2004. Modarres R and Parkin R (2004) Cryptosporidiosis Susceptibility and Risk: A Case Study, Risk Analysis, 10.1111/j.0272-4332.2004.00424.x, 24:1, (209-220), Online publication date: 1-Feb-2004. Parkin R (2004) Addressing Susceptibility in Microbial Pathogen Risk Assessment, Human and Ecological Risk Assessment: An International Journal, 10.1080/10807030490281025, 10:1, (135-149), Online publication date: 1-Feb-2004. Krewski D, Balbus J, Butler-Jones D, Haas C, Isaac-Renton J, Roberts K and Sinclair M (2004) MANAGING THE MICROBIOLOGICAL RISKS OF DRINKING WATER, Journal of Toxicology and Environmental Health, Part A, 10.1080/15287390490491909, 67:20-22, (1591-1617), Online publication date: 1-Oct-2004. Parkin R, Soller J and Olivieri A (2003) Incorporating susceptible subpopulations in microbial risk assessment: pediatric exposures to enteroviruses in river water, Journal of Exposure Science & Environmental Epidemiology, 10.1038/sj.jea.7500265, 13:2, (161-168), Online publication date: 1-Mar-2003. Krewski D, Balbus J, Butler-Jones D, Haas C, Isaac-Renton J, Roberts K and Sinclair M (2011) MANAGING HEALTH RISKS FROM DRINKING WATER--A REPORT TO THE WALKERTON INQUIRY, Journal of Toxicology and Environmental Health, Part A, 10.1080/00984100290071711, 65:21, (1635-1823), Online publication date: 20-Oct-2002. Brown M (2002) Exposure assessment Microbiological Risk Assessment in Food Processing, 10.1533/9781855736689.1.100, (100-126), . Privitera G, Porretta A and Panceri M (2001) Pandora's box: Old and new emerging infections in at-risk populations, American Journal of Infection Control, 10.1067/mic.2001.115682, 29:4, (222-224), Online publication date: 1-Aug-2001. Vol. 108, No. 9 September 2000Metrics About Article Metrics Publication History Originally published1 September 2000Published in print1 September 2000 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

The Beta Poisson dose-response model is not a single-hit model.

The choice of a dose-response model is decisive for the outcome of quantitative risk assessment. Single-hit models have played a prominent role in dose-response assessment for pathogenic microorganisms, since their introduction. Hit theory models are based on a few simple concepts that are attractive for their clarity and plausibility. These models, in particular the Beta Poisson model, are used for extrapolation of experimental dose-response data to low doses, as are often present in drinking water or food products. Unfortunately, the Beta Poisson model, as it is used throughout the microbial risk literature, is an approximation whose validity is not widely known. The exact functional relation is numerically complex, especially for use in optimization or uncertainty analysis. Here it is shown that although the discrepancy between the Beta Poisson formula and the exact function is not very large for many data sets, the differences are greatest at low doses--the region of interest for many risk applications. Errors may become very large, however, in the results of uncertainty analysis, or when the data contain little low-dose information. One striking property of the exact single-hit model is that it has a maximum risk curve, limiting the upper confidence level of the dose-response relation. This is due to the fact that the risk cannot exceed the probability of exposure, a property that is not retained in the Beta Poisson approximation. This maximum possible response curve is important for uncertainty analysis, and for risk assessment of pathogens with unknown properties.

Epidemiology, Microbiology, and Risk Assessment of Waterborne Pathogens Including Cryptosporidium

Cryptosporidium is one of a suite of relatively recently emerging pathogens of concern in drinking water. Based on human dose–response tests, guidelines for exposure yielding defined levels of endemic risk have been developed. This risk assessment procedure is grounded in the process used for chemical risk assessment. From outbreak data, critical concentrations in water that may lead to epidemic levels have been postulated. Development of these levels will be discussed. Validation of the information using outbreak reports from the 1993 Milwaukee incident can be made. Use of this approach must be tempered by the existence of substantial waterborne cases in the absence of detectable oocyst levels as in the Las Vegas outbreak, and (apparent) high levels of oocysts without (apparent) significant health effects as in the case of the (at the time of this writing) ongoing incident in Sydney, Australia.

Risk assessment of opportunistic bacterial pathogens in drinking water.

This study was undertaken to examine quantitatively the risks to human health posed by heterotrophic plate count (HPC) bacteria found naturally in ambient and potable waters. There is no clear-cut evidence that the HPC bacteria as a whole pose a public health risk. Only certain members are opportunistic pathogens. Using the four-tiered approach for risk assessment from the National Academy of Sciences, hazard identification, dose-response modeling, and exposure through ingestion of drinking water were evaluated to develop a risk characterization, which estimates the probability of infection for individuals consuming various levels of specific HPC bacteria. HPC bacteria in drinking water often include isolates from the following genera: Pseudomonas, Acinetobacter, Moraxella, Aeromonas, and Xanthomonas. Other bacteria that are commonly found are Legionella and Mycobacterium. All these genera contain species that are opportunistic pathogens which may cause serious diseases. For example, the three nonfermentative gram-negative rods most frequently isolated in the clinical laboratory are (1) Pseudomonas aeruginosa, (2) Acinetobacter, and (3) Xanthomonas maltophilia. P. aeruginosa is a major cause of hospital-acquired infections with a high mortality rate. Aeromonas is sometimes associated with wound infections and suspected to be a causative agent of diarrhea. Legionella pneumophila causes 4%-20% of cases of community-acquired pneumonia and has been ranked as the second or third most frequent cause of pneumonia requiring hospitalization. The number of cases of pulmonary disease associated with Mycobacterium avian is rapidly increasing and is approaching the incidence of M. tuberculosis in some areas. Moraxella can cause infections of the eye and upper respiratory tract. The oral infectious doses are as follows in animal and human test subjects: P. aeruginosa, 10(8)-10(9); A, hydrophila, > 10(10); M. avium, 10(4)-10(7); and X. maltophilia, 10(6)-10(9). The infectious dose for an opportunistic pathogen is lower for immunocompromised subjects or those on antibiotic treatment. These bacteria have been found in drinking water at the following frequencies: P. aeruginosa, < 1%-24%; Acinetobacter, 5%-38%; X. maltophilia, < 1%-2%; Aeromonas, 1%-27%; Moraxella, 10%-80%; M. avium, < 1%-50%; and L. pneumophila, 3%-33%. These data suggest that drinking water could be a source of infection for some of these bacteria. The risk characterization showed that risks of infection from oral ingestion ranged from a low of 7.3 x 10(-9) (7.3/billion) for low exposures to Aeromonas to higher risks predicted at high levels of exposure to Pseudomonas of 9 x 10(-2) (98/100). This higher risk was only predicted for individuals on antibiotics. Overall, the evidence suggests that specific members of HPC bacteria found in drinking water may be causative agents of both hospital- and community-acquired infections. However, the case numbers may be very low and the risks represent levels generally less than 1/10,000 for a single exposure to the bacterial agent. Future research needs include (1) determining the seasonal concentrations of these bacteria in drinking water, (2) conducting adequate dose-response studies in animal subjects or human volunteers, (3) determining the health risks for an individual with multiple exposures to the opportunistic pathogens, and (4) evaluating the increase in host susceptibility conferred by antibiotic use or immunosuppression.