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Pathogen Source Tracking
Overview
Scientists are developing novel techniques for rapidly detecting and tracking marine microbes of public health concern including bacteria, viruses, protozoan parasites, and harmful algal bloom (HAB) species. These tools will be useful for rapidly assessing health risks for humans who swim in coastal waters or consume shellfish. This technology will also allow the sources of microbes to be identified, assisting managers in formulating strategies to reduce contamination.
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Background, Approach and Rationale
Many bacterial, viral, and protozoan pathogens, and algal toxins, exist in coastal environments and pose a threat to public health. Some microorganisms of public health concern are indigenous to the oceans, including vibrios, mycobacteria, and toxin-producing algae. Other microorganisms are introduced through fecal material. These foreign microbes include enteric bacteria such as Escherichia coli, Salmonella spp. and Shigella spp., enteric viruses including Noroviruses, Hepatitis A and some Caliciviruses, and protozoan parasites including Cryptosporidium parvum and Giardia lamblia. Foreign microbes enter coastal oceans via agricultural and urban surface runoff, wastewater discharges, storm water drainage systems, and from domestic and wild animals.
Human exposure to these pathogens occurs by ingesting contaminated seafood or seawater, or by exposure of open wounds to contaminated water. The risk of human exposure can be particularly high at beaches, tidal creeks, estuaries, and in brackish stormwater detention ponds, where intimate human exposure occurs through recreational activities such as fishing, crabbing, golfing, boating, waterskiing, and swimming.
Detection methods for most microorganisms of public health concern are inadequate. Traditional methods rely on microscopy or cultivation, both of which are labor intensive and are only applicable to a limited number of organisms. Assays of indicator bacteria, i.e., coliforms or enterococcus, have been adopted as an alternative to direct detection of enteric pathogens. These indicator assays are slow, requiring over 24 hours to obtain results, and they do not provide information about sources of pollution. In 2002, 87% of the more than 12,000 reported beach closings and swim advisories were attributed to high levels of these indicator bacteria. The source of bacteria was listed as unknown in 62% of these instances (NRDC, 2003). Another problem with the indicator system is that their detection may not be indicative of all pathogenic microbes, particularly viruses and protozoa. Pathogenic viruses have been repeatedly isolated from shellfish and coastal waters that were in compliance with standard bacteriological criteria (Croci et al., 2000; Muniain-Mujika et al., 2000, 2003; Dore et al., 2000). Rapid and specific microbial methods are needed to assess pathogen presence in coastal oceans, and to estimate risk of exposure among susceptible persons through recreational water use or shellfish consumption. Methods are also needed to track the sources of microbial pollution so that effective remediation strategies and more accurate risk analyses can be developed.
The main goal of research conducted within the HML OHH microbiology program will be to develop novel molecular techniques capable of rapidly detecting marine microbes that threaten human health. The approach will be collaborative, integrating resources from four NOAA laboratories (Center for Coastal Environmental Health and Biomolecular Research (CEHBR), the Center for Coastal Fisheries and Habitat Research (CCFHR), the NOAA Cooperative Oxford Laboratory, and the Atlantic Oceanographic and Meteorological Laboratory (AOML)); HML academic and state partners (College of Charleston, Medical University of South Carolina, South Carolina Department of Natural Resources, and the National Institute of Standards and Technology); and a National Institute of Health Sciences⁄National Science Foundation Ocean and Human Health Center (the University of Miami Rosenstiel School of Marine and Atmospheric Science), to build the capability of HML⁄CCEHBR to track marine microorganisms of public health significance. An array of organisms will be targeted, including some that are host-specific. Detection of these host-specific organisms will also provide information about pollution sources. The proposed assays will be developed, verified, field tested, and included in ecosystem monitoring and assessment programs. This research will complement current efforts within NOAA to develop microbial source tracking techniques and rapid pathogen detection methods.
Projects
- Pathogen Source Tracking–Library Independent Methods
- Adapting Luminex to Microbial Source Tracking
- PATHSCAN and PATHCAST
- Use of Molecular Techniques to Detect Emerging Pathogens
- HAB Identification Tools
- Development of Novel Technologies to Track Multiple Drug Resistant E. coli
Literature Cited
Croci, L., D. De Medici, C. Scalfaro, A. Fiore, M. Divizia, D. Donia, A.M. Cosentino, P. Moretti, and G. Costantini (2000). Determination of enteroviruses, hepatitis A virus, bacteriophages and Escherichia coli in Adriatic Sea mussels. J Appl Microbiol. 88(2):293-8.
Dore, W.J., K. Henshilwood, and D.N. Lees (2000). Evaluation of F-specific RNA bacteriophage as a candidate human enteric virus indicator for bivalve molluscan shellfish. Appl Environ Microbiol. 66(4):1280-5.
Muniain-Mujika, I., R. Girones, and F. Lucena (2000). Viral contamination of shellfish: evaluation of methods and analysis of bacteriophages and human viruses. J Virol Methods. 89(1-2):109-18.
Muniain-Mujika, I., M. Calvo, F. Lucena, and R. Girones (2003). Comparative analysis of viral pathogens and potential indicators in shellfish. Int J Food Microbiol. 83(1):75-85.
NRDC (2003). Testing the Waters 2003: A Guide to Water Quality at Vacation Beaches. Natural Resources Defense Council Pubications. New York.