Impact/Purpose:

Use animal studies to validate molecular-based assays concerning the virulence of microorganisms. Identify pathogenic strains of bacterial species known to include opportunistic pathogens and identify currently unknown opportunistic pathogens among the heterotrophic bacteria that occur in drinking water or biofilms.

Description:

The heterotrophic bacteria that are indigenous to potable water are normally not a threat to the healthy population. However, some strains of Aeromonas hydrophila, Legionella pneumophila and the nontuberculous mycobacteria are opportunistic pathogens that can cause illness and sometimes death in individuals with impaired immune systems. Within a given species there may be virulent and avirulent strains and this distinction is often not easily determined. The in vitro virulence tests currently available are insufficient to correctly identify the virulent strains. Animal models are the best means of correctly classifying strains according to their pathogenic potential. Animal models will be used to identify pathogenic strains of Contaminant Candidate List (CCL) bacteria from the Aeromonas hydrophila group, the genus Legionella and the Mycobacterium avium complex. Strains identified as pathogenic as well as control strains identified as non-pathogenic will be used to validate rapid tests for virulence using DNA microarrays. Animal models will also be used to screen concentrated flora from potable water samples to possibly identify unknown opportunistic pathogens and to analyze some newly discovered organisms that parasitize amoebae for potential pathogenicity. The data obtained on known opportunistic pathogens will be used not only to develop DNA microarray tests for virulence but also to assess the virulence of Aeromonas, Mycobacterium and Legionella strains isolated in occurrence studies and to help determine whether or not these organisms should be considered for future regulations. If any currently unrecognized pathogens are found in the studies of amoeba or the mixed bacterial flora, the organisms will be characterized and will be considered as candidates for future CCL lists.

Record Details:

Record Type:PROJECT

Start Date:01/01/2003

Projected Completion Date:09/01/2008

OMB Category:Other

Record ID: 56095

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Project Information:

Progress :This is one of five tasks in MCEARD for understanding and characterizing the use of virulence factors to predict the hazard that microorganisms may pose to humans. Intraperitoneal exposure studies in mice have been initiated. Dose ranges and virulence capabilities of Aeromonas strains are being determined. Strains of Aeromonas tested have included hydrophila, caviae, veroni/sobria, salmonicida, enchelia, and allosaccharophila. A promising new procedure for monitoring the ability of bacteria to cause diarrhea in mice is currently being studied. This procedure will be very useful in determining virulence capabilities of opportunistic bacterial pathogens for gastrointestinal infections.

Relevance : A database will be developed that will be useful in establishing and evaluating molecular-based assumptions concerning virulence factor activity relationships of current and prospective candidates for the CCL list. The results of this study should allow us to distinguish between virulent and avirulent isolates of CCL pathogens of the Aeromonas hydrophila group and the Mycobacterium avium complex. Ability to distinguish virulent strains of Aeromonas and Mycobacterium avium will be useful to assess the occurrence and the risk of virulent forms of these species in potable water and determine whether it is necessary to regulate them. It is possible that this study will identify currently unknown opportunistic bacterial or fungal pathogens in potable water that may be causing some of the illnesses of unknown etiology that occur every year. Any new pathogens would be potential candidates for the next CCL list.

Clients :Dr. Paul Berger, OGWDW

Project IDs:

ID Code :13336

Project type :OMIS