New test for bacterial contamination

Tuesday, April 13, 2010 @ 06:04 PM gHale


There is now a process to analyze bacterial concentrations in the water at a beach and get results in under one hour, through the development of a new in-field, rapid-detection method.

The analysis process now takes a minimum of 24 hours and since bacteria levels can change quickly in the water column, a one-day turnaround time simply isn’t fast enough to adequately protect swimmers or prevent unnecessary beach closures, the engineers say.

Jenny Jay, associate professor of civil and environmental engineering at UCLA’s Henry Samueli School of Engineering and Applied Science, and Ph.D. student Christine Lee advanced and tested a rapid method in marine and freshwater samples from beaches in Malibu and Santa Monica. It is among the first viable in-field methods for rapid, portable fecal bacteria analysis.

Even for areas like the Southern California coast, which are close to state-of-the-art laboratories, transportation time, coupled with lab work, may mean that results often are not ready until the next day. With such a delay between sampling and results, the results may no longer be relevant due to the dynamic nature of water quality in beach environments.

The new rapid method represents a field-portable alternative to more expensive procedures, particularly where larger-scale, expensive equipment is not readily accessible. To decrease the time to determine results, the researchers outfitted a portable kit to test samples for bacterial concentrations.

“We envision a tool that can be used by lifeguards to collect and analyze water samples throughout the day, providing beachgoers with up-to-date, near-real-time data on water conditions,” Lee said. “This could also be useful in determining persistence of a bacterial contaminant after a pollution event, such as a sewage spill or a septic tank leaking.”

“We are currently applying this method, in a new approach, to identifying contamination sources in which we can adaptively sample the environment in order to hone in on hotspots,” Jay said.

The process uses magnetic beads conjugated to specific antibodies that identify and bind fecal bacteria used as standards for determining the safety of recreational waters, such as E. coli and Enterococcus.

After a few filtration and isolation steps, researchers break down the sample organisms and treat them with an enzyme that catalyzes a light-emitting reaction with target ATP, the energy currency of a cell. Cells break down ATP to obtain energy important for cellular processes.

Scientists can then determine bacterial concentrations based on how much released light there is by using a luminometer, a device that detects light emissions.

The process is covalently linked immunomagnetic separation/adenosine triphosphate quantification technique (Cov-IMS/ATP).

For the Southern California coast, using this detection method would be a big boost for the region.

“It could result in faster notification of the public on the health risks of swimming at contaminated beaches and better protection of public health,” said Mark Gold, D.Env., president of the environmental group Heal the Bay.

In California, where gastrointestinal illness that can result from contact with contaminated beach water, estimates show it could cost Orange and Los Angeles county beach visitors between $21 million and $51 million per year in sick days and related issues.

Furthermore, California coastlines are subject to chronic water pollution problems due to sewage spills and urban runoff. Rainstorms in Southern California can further exacerbate this problem, as pollutants accumulated over time on street surfaces suddenly flush into the ocean.



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