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Exposure Research

EPA scientists collaborate in development of rapid methods to identify and measure specific pathogens in drinking water

EPA microbiology scientists are working with NanoLogix, Inc. — a U.S.-based company specializing in live-cell rapid diagnostics — to develop new, rapid, sensitive cost-effective methods for detecting and identifying protozoan and bacterial pathogens in drinking water systems. Such methods would be used by epidemiologists to investigating drinking water pathogen outbreaks.

Current culture-based methods, used to identify and measure specific pathogens during an outbreak, can take up to 2 to 3 days to get results. These new methods would be especially helpful in detecting Cryptosporidium and also E. coli O157:H7 — a strain that can cause serious diarrhea.

The microbiologists are collaborating to improve recoveries of Crypotosporidium oocysts in source waters that feed drinking water systems. They’re using a new immunomagnetic separation procedure being developed by NanoLogix. Increasing recovery rates and establishing greater consistency in results over time can allow more accurate quantification of Cryptosporidium oocysts, which can provide more reliable scientific information on which to base water treatment decisions. This research is part of a Cooperative Research and Development Agreement signed in July 2010.

Currently, EPA and NanoLogix scientists are entering the second phase of research in which scientists are seeking to improve recoveries of E. coli O157:H7 from source water using the same immunomagnetic separation technology, followed by growth on a solid medium using the company’s patented membrane procedure. This procedure promotes rapid growth of bacterial pathogens, due to the increased permeability of the patented filters.

The scientists expect that the membrane procedure will enable them to identify their strain of E. coli more rapidly than current methods allow. Improved recoveries and rapid identification of this type of E. coli will provide scientists with more accurate data on the occurrence of these organisms in drinking water sources, and will enhance EPA’s ability to conduct quantitative microbial risk assessments.

“We believe we will be able to come up with a method for E. coli O157:H7 that will allow us to skip the enrichment step and reduce detection time to less than 24 hours,” said EPA microbiologist Dr. Gerard Stelma. “Eliminating the enrichment step will also make the method more quantitative.”

“In the near future, we would like to have a couple of papers ready for publication, as well as a complete method for the environmental community to use,” Stelma said. “Due to the promising results we have seen thus far, it is possible that we may have more than one method available.”

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