Molluscan Shellfish Aquaculture by Sandra Shumway;

Author:Sandra Shumway;
Language: eng
Format: epub
Publisher: International Specialized Book Services
Published: 2021-02-15T00:00:00+00:00

Microbial Source-Tracking (MST)

Simply stated, the goal of MST is to determine the host specie, or species, associated with fecal contamination. This information would be of value in the identification and remediation of pollution sources associated with the host species of concern and would improve the assessment of public health risk. At present, MST is an evolving and complicated science that presents numerous challenges to its use in sanitary surveys. Unlike the traditional, more general indicator organism assays (for example, fecal coliform [FC]), there is not yet a standard method for MST or one agreed upon approach that is available for use. The various experimental methods have used a variety of microbiological species as the indicator organism, including FC, E. coli, fecal streptococci, enterococci, anaerobic enteric bacteria in the Bacteroidales order, adenovirus, and coliphage, a virus that infects E. coli. A variety of molecular and biochemical detection methods continue to be investigated as well, including several forms of polymerase chain reaction (PCR), antibiotic resistance, biochemical fingerprinting, and ribotyping. Microbial source-tracking (MST) methodologies further divide into library-dependent and library-independent methods. The former relies on the development of a large collection of genetic fingerprints for the various potential fecal sources in the area, against which the genetic information from samples are matched using sophisticated statistical techniques (for example, discriminant analysis). The library-independent methods rely on the use of indicator organisms that are thought to be specific to a particular animal host (for example, cattle); method comparison studies have shown the library-independent methods to perform better than the library-dependent methods and the former are now the focus of most MST research. The current MST approaches are essentially qualitative, lacking the ability to determine the relative pollution load associated with each animal or human source. Although still in the research and development phase, there may be some useful applications of a qualitative MST method as an adjunct to the traditional sanitary survey process. Ultimately, however, there will be the need to determine the relative contribution of each source if the goal is to identify the major pollution sources and achieve a significant reduction in fecal contamination through prioritized remediation activities.

Microbial source-tracking is also a costly technology and often well beyond the financial resources of the SCA or a broader stakeholder group interested in determining sources of fecal contamination. In most cases a thorough shoreline and sanitary survey will be successful in discovering and assessing the various pollution sources, allowing the SCA to estimate their relative contribution to the overall pollution load reaching the proposed growing area. Conversely, there are occasional circumstances when the sanitary survey process identifies water quality impacts in the growing area that may not be consistent with observations and water quality data for the watershed and surrounding shoreline. In these cases, there is an argument for exploring the use of MST to potentially gain a better understanding of the host organisms contributing fecal contamination to the area. There is a steep learning curve involved with MST and it is advised that the

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