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item Ibekwe, Abasiofiok - Mark

Submitted to: Pathogens in the Environment Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/20/2003
Publication Date: 1/20/2004
Citation: Ibekwe, A.M., Jenkins, M. 2004. Identifying and quantifying sources of bacteria. In: Hargrove, W.L., editor. Pathogens in the Environment Workshop Proceedings, Feb. 23-25, 2004, Kansas City, MO. p. 18-21.

Interpretive Summary: The development of bacterial source tracking is of great interest to many federal, state, and local agencies as this will aid in identification of major sources of water pollution. At present, several methods are being developed and several indicator organisms are used by different researchers. Of the indicator bacteria, USEPA is most interested in Escherichia coli and Enterococci. In our laboratory, we are using E. coli and Enterococci for bacterial source tracking. We are using the two because, E. coli is a known quantity and many studies have been conducted with the bacterium for source tracking. Very few studies have been done with Enterococci for bacterial source tracking. Our studies are performed by monitoring the presence of E. coli, Enterococci, and Bacteroides thetaiotaomicron in water samples obtained from various sites along Santa Ana River that are impacted by wastewater discharge, urban runoff, subsurface water, and agricultural discharge. Data obtained from this study will be part of the national database maintained by USDA for bacterial source identification. Since bacterial source tracking requires large database, a multi-lab effort is required at the moment. At the end of this project, a genetic fingerprinting method in combination with specific DNA markers will be available that will be part of the database.

Technical Abstract: Pathogen contamination is the second leading cause for placing surface waters on the 1998 303(d) list of impairments, second only to sediments. Contamination by pathogens accounts for 13% of all impairments, with a total of 5281 nationwide. Bacterial source tracking (BST) is an essential tool for addressing all aspects of Total Maximum Daily Load (TMDL). When applied to pathogen-impaired waters, it can be used to define water-quality problems in watersheds across the nation. These methods monitor the levels of fecal coliforms and bacteria that live in the gastrointestinal tract of animals and survive in the environment when expelled with feces. While some of these techniques are promising, most are still in the early stages of development. Many of these techniques have been tested in a limited number of watersheds and with a limited number of possible sources. Recently, the U.S EPA released a report that calls for a sustained nationwide study to test, compare, and improve bacterial source tracking methods. Bacterial source tracking (BST) is a term that was first coined by Hagedorn and Wiggins of Virginia Tech. It includes various sub-typing methods, such as antibiotic resistance analysis, pulsed-field gel electrophoresis, ribotyping, restriction fragment length polymorphism, and amplified fragment length polymorphism, to differentiate between the sources of indicator bacteria in natural waters and their host origins. The issue in water-quality assessment depends upon knowledge of the source (human, dog, cattle, wild animals, etc) of contamination. Information from these methods can be used for accurate risk analysis, effective remediation, and valid total maximum daily load assessment.