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BACTERIAL PATHOGENIC RESEARCH IN RESPONSE TO CONTAMINANT CANDIDATE LIST NEEDS
Citation:
McDaniels, A E., T C. Covert, A A. De La Cruz, AND M R. Rodgers. BACTERIAL PATHOGENIC RESEARCH IN RESPONSE TO CONTAMINANT CANDIDATE LIST NEEDS. Presented at EPA Science Forum 2002, Washington, DC, April 30-May 2, 2002.
Impact/Purpose:
Investigate the occurrence of Aeromonas bacteria in potable water derived from both surface and ground water sources. Develop improved method(s) for the detection of culturable H. pylori in environmental samples and investigate the occurrence of H. pylori in potable waters.
Description:
The Safe Drinking Water Act, as amended in 1996, requires EPA to establish a Contaminant Candidate List (CCL) of unregulated microbiological and chemical contaminants to aid in priority setting for the Agency's drinking water program. At predetermined intervals the Agency must select five or more contaminants from the current CCL and determine whether they should be regulated. Information on where these contaminants occur and the extent of exposure in humans, with particular emphasis on the effects that these contaminants have on sensitive subpopulations, such as infants, children, pregnant women, the immunocompromised, and the elderly, will be needed to support any future regulatory decisions.
There are four bacteria on the current CCL: Mycobacterium avium complex, Aeromonas, Helicobacter pylori and cyanobacterial toxins. Each of these is different with regard to the state of the art of the available detection methodologies and therefore our knowledge of their possible occurrence in distribution system drinking water. We know that Mycobacterium avium complex bacteria occur naturally in the environment and are relatively resistant to standard disinfection practices. A typical cultural assay for these organisms can take up to eight weeks to complete and the sensitivity of the assay is low due to the harsh decontamination steps necessary to prevent overgrowth of faster growing competing bacteria. We have developed a molecular DNA method which includes a one week enrichment step. We have demonstrated good agreement between this molecular method and the standard cultural assay. Aeromonas bacteria are also naturally occurring in all fresh waters and have been found in distribution system water, possibly due to their multiplication in biofilm material. Our evaluation, modification and validation studies have resulted in EPA Draft Method 1605. This method will be utilized in the monitoring requirements of the Unregulated contaminant Monitoring Rule. Our work with cyanobacteria, another commonly encountered group of bacteria in environmental waters, is focused on the toxins these organisms produce and we are developing sensitive methods based on the use of bio-sensors. The natural source(s) Helicobacter pylori, the causative agent of most gastric ulcers and the only recognized bacterial carcinogen, are unknown, as are the primary routes of its transmission in humans. We are developing and evaluating both cultural and molecular methods of detection for this important pathogen.