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Faster Water Quality Results Provide Safer Swimming

Faster Water Quality Results Provide Safer Swimming

DNA-based technique detects bad bacteria in freshwater beaches

Steve Mauro

Thursday, July 12, 2012 - 16:45

Allison Jarrell, Contributor

(Inside Science) -- After a morning of packing swimming gear, applying sunscreen and driving to the nearest beach, the last thing anyone wants to see is a red flag flying high in the sand. Such a warning tells beachgoers that the water is most likely contaminated with E. coli or other pathogens.

Testing for the presence of E. coli bacteria is the current and most common practice for measuring the safety of fresh water. Unfortunately, it can take 24 hours to produce results with normal methods. In other words, the red flag taunting you is most likely an indicator of yesterday's water conditions and is quite possibly no longer relevant. This lag in information opens the possibility that swimmers can enter a contaminated beach that was safe a day ago, or be barred from entering a beach that has since cleared up.

Scientists are working to decimate these delays. This summer, biologist Steven Mauro from Mercyhurst University in Erie, Pa., is testing a new method that takes only a couple of hours to produce water-quality results for freshwater beaches.

Mauro has spent the past few years collaborating on the project with scientists from the Erie-based nonprofit Regional Science Consortium, Pennsylvania's Department of Conservation and Natural Resources, the Erie County Department of Health and Penn State Behrend. He and his team have established a rapid method of testing the quality of beach water at Presque Isle, which often has occurrences of elevated E. coli levels.

"Thus far, we've been over 90 percent accurate in predicting whether E. coli levels would be high or not for this summer," Mauro said.

The new method combines a computer model with a technique called quantitative PCR, which stands for polymerase chain reaction. It's used to detect the DNA of specific bacteria called bacteroides, which indicates the presence of E. coli.

"You can actually count how many original copies of that DNA that you had," Mauro said. "You're able to pull out the particular bacteria that you're looking at from the environmental sample."

Penn State Behrend statistician Michael Rutter developed a predictive computer program that measures real-time water conditions, including wind direction and speed, water temperature and wave height, to predict when conditions are ripe for E. coli contamination.

Mauro monitors the program's calculations every morning and, if contamination is suspected, takes beach water samples and processes the DNA back at his lab using the qPCR technique. If the results confirm a high risk of E. coli contamination, Mauro reports his findings to Presque Isle beach managers who can then issue timely safety warnings.

"Wave action and rain events are big factors in E. coli contamination," Mauro said. "The E. coli is used as a predictor of bad microbes that are commonly associated with gastrointestinal illnesses. Those are the ones we hope to prevent."

Several other researchers and beach managers across the U.S. have been experimenting with similar rapid testing methods. Cathy Breitenbach, director of lakefront operations at the Chicago Park District, has implemented a statistical model for predicting water quality at 15 Chicago beaches this summer while also continuing traditional testing.

Over the past year, Breitenbach’s team has been collecting data including wave height and period, water temperature, rainfall, wind data and turbidity, which is the loss of transparency due to the presence of particles such as silt. During the winter, the district worked with the U.S. Geological Survey to develop statistical models.

"Anecdotally, they're doing better than traditional testing," Breitenbach said. "We haven't caught everything, but we have been able to get advisories up, where last year we would have missed them until the following day."

Mauro and his team hope to broaden their horizons by experimenting at other beaches and testing seawater in the future. Their current method is applicable only to fresh water, because salt water is usually tested for Enterococcus bacteria rather than E. coli.

"I think this will be something that is easy to implement across the nation," Mauro said. "At the end of the day, each beach will have to determine its own levels [of bacteria] that would be predictive of E. coli. It involves some type of pre-work, and that could be costly. But once the system is in place, it's actually very affordable."

Allison Jarrell is a contributing writer to Inside Science News Service.



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