Bacterial Source Tracking (BST)
Brief Overview of BST
WHAT IS BST?
BST or Bacterial Source Tracking is new methodology that is being developed to determine the sources of fecal bacteria from environmental samples (e.g. from human, livestock, or wildlife origins). BST methodology has been described as having the ability to turn nonpoint sources into point sources. In the scientific literature BST is also called fecal sourcing or fecal typing. BST is new and novel, and must be considered very experimental at present.
WHY HAS BST APPEARED ONLY RECENTLY?
Funding for BST research has only become available in the last few years. The recent implementation of the Total Maximum Daily Load (TMDL) concept by EPA is the driving force behind BST development. BST methods represent the best tools available for determining sources of fecal pollution in water, and should be an integral part of any project that involves TMDL development for fecal coliforms, or design and implementation of Best Management Practices (BMP) to reduce fecal loading in water.
WHAT TYPES OF BST METHODS ARE UNDER DEVELOPMENT?
Both molecular (genotype) and biochemical (phenotype) BST methods are under development (see the BST METHODS page). DNA fingerprinting has received the greatest publicity, but to date there are at least ten or so different methods described in the scientific literature that show potential. However, BST development is so new that no research comparing BST methods or identifying their relative strengths and weaknesses has yet been completed. Such comparison research has only recently been started, and results should become available over the next few years. At this point it seems reasonable to assume that some combination of BST methods will be needed to provide the most accurate and reliable source identification answers. It is doubtful that any one BST method will emerge as the "best" method for all situations.
Molecular methods may offer the most precise identification of specific types of sources, but are limited by high per-isolate costs, detailed and time-consuming procedures, and are not yet suitable for assaying large numbers of samples in a reasonable time frame. Biochemical methods may or may not be as precise, but are simpler, quicker, less costly, and allow large numbers of samples to be assayed in a short period of time. Perhaps the best approach at this point is to use a biochemical method to determine sources on large numbers of fecal bacterial isolates, and then confirm (validate) both the method and the results by assaying some smaller subset of isolates with a molecular procedure.
HOW WELL DOES BST WORK?
At present, BST can reliably determine if fecal bacteria are from human or animal sources. If the bacteria are from animal sources, BST can also tell if the animals are livestock or wildlife, but less reliably than the human vs. animal separation. It is unknown at this time if BST can eventually achieve distinctions between different types of livestock (e.g. cattle, horse, swine, poultry, etc.) or wildlife (e.g. deer, waterfowl, racoon, etc.) or pets (dogs, cats, etc.). Many in the molecular biology community believe such fine differentiations are feasible.
HOW WILL BST BE USED BY REGULATORY AGENCIES?
BST will be heavily used by regulatory agencies in the future. For example, in Virginia fecal coliform bacteria are the most widespread pollutant in rivers and streams. Over 60% of the stream segments in Virginia that have been evaluated to date are listed as impaired waters due to fecal coliform populations that exceed water quality standards. Most states face a similar situation. The ability to develop realistic TMDLs for fecal bacteria, and implementation of cost-effective BMPs for watershed restoration will largely depend on using the new BST methodology to accurately identify sources of fecal pollution in water.
THE BOTTOM LINE!
BST methodology is here and it does work, even though it is still must be considered
experimental. Look for BST to be widely used in the near future and to be developed
very rapidly. To get to that "widely used" stage, guess what is lacking?
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| BST OVERVIEW
| BST METHODS
| BST LABS | BST
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BST website maintained by Charles Hagedorn, Professor of Crop and Soil Environmental Sciences, Va Tech.