Technology

NIST is working with the EPA to develop standards for improving fecal contamination measurements in recreational waters.

The plasmid DNA of the fecal indicator developed by SRM 2917, EPA is standardized with 13 genetic markers (known DNA sequences) that can be used to identify the source of contamination and to estimate the concentration of fecal contamination in the sample. This is a reference material.

credit:

J. Kralj / NIST

As the summer beach season approaches, you may see a “no trespassing” sign indicating that it is temporarily closed. If fecal contamination is suspected, public health authorities can perform lab tests on water samples to see if it is safe for people to swim in the water.

Results are not always consistent, despite the many lab methods available to health authorities. To help resolve this issue, the National Institute of Standards and Technology (NIST) has been working with the Environmental Protection Agency (NIST).EPA) Develop a reference (known as the EPA-developed SRM 2917 plasmid DNA for fecal indicators) to ensure overall more accurate results for the method used by public health authorities.

“The main purpose of the development of the NIST SRM2917 was to develop tools that could be used to standardize the use of national water quality monitoring methods and establish performance indicators for the methods,” said Orin Shanks, a research geneticist at the EPA. Mr. says. About the development of SRM with NIST researchers. “SRM also helps scientists, managers and the general public evaluate the quality of measurements.”

EPA is responsible for developing monitoring tools Recreational water qualityIncludes beaches, lakes and rivers used for fishing, boating, swimming, surfing and other purposes. According to Shanks, fecal contamination of these waters includes septic tank failures, sewer leaks, stormwater drainage, agricultural spills, merging sewer overflows, improper disposal of wildlife and pet excrement, and illegality. It may be due to the act.

People exposed to fecal contamination by contacting the skin or swallowing water can suffer from mild to potentially fatal illnesses. Children, the elderly, and people with weakened immunity may be at high risk.

Designed to mitigate this problem, NISTSRM2917 contains 13 genetic markers (known DNA sequences) that can be used to identify sources of contamination and estimate fecal contamination concentrations in samples. SRM was constructed from plasmids, which are small, often circular DNA molecules found in bacteria and other cells.

NIST Robotler Machine

When compiling a standard reference material (SRM), researchers use what is called a “robotler.” This is a robot machine programmed to automatically fill test tubes. SRM 2917 (EPA-developed plasmid DNA for fecal indicators) consists of 13 known DNA sequences (gene markers) that can be used to estimate the concentration of fecal contamination in a sample. Here, the SRM tube is filled with a plasmid DNA sample. Credit: J. Kralj / NIST

The EPA has selected a genetic marker for SRM. Some of them rely on more than a decade of collaborative research. Genetic markers on plasmid DNA serve as indicators of fecal contamination. “Fecal indicators are targets such as bacteria and genetic markers that indicate fecal contamination,” said Scott Jackson, a researcher at NIST. “There are a total of 13 genetic markers, some of which detect human feces, cattle, bird and dog feces. Therefore, it is possible to distinguish which fecal source is present in a contaminated water sample. I can do it.”

Each genetic marker in SRM works with a specific qPCR method designed to characterize fecal contamination of water samples. The qPCR assay (quantitative polymerase chain reaction) is a molecular test used to estimate sample target DNA concentrations that rely on references to interpret the results. Three of these test methods have been nationally validated by the EPA.

The qPCR method targets two types of fecal indicators. The first estimates the total amount of feces in the sample and the second identifies the cause of fecal contamination. The two qPCR methods target fecal index bacteria. E. coli When Enterococcus, It is found in the fecal waste of most mammals. The remaining 11 qPCR methods help identify sources such as human, cow, dog, pig, and bird droppings.

“This is a versatile reference. Future laboratories can use this SRM to determine if water can swim safely and identify the source of water for fecal contamination.” Shanks said.

What makes SRM so novel is that all 13 genetic markers are in one physical DNA, says NIST researcher Jason Kralj. This means that researchers can use one standard to evaluate the results of multiple qPCR methods from water samples.

SRM can be used to minimize variability in water quality measurements between laboratories and to assist in the lab certification process. This indicates that the public health lab is running the test correctly. Although the SRM was developed for regular recreational water quality testing, it can also be used to support rainwater management, food production monitoring, wastewater monitoring, and route identification, Shanks said. ..

During the development of SRM, national inter-laboratory research was conducted. In the near future, NIST and EPA will publish findings designed to assess SRM performance nationwide.

“For the future, the success of this collaboration could lead to future collaborations focused on developing new references to support the implementation of methodologies designed to protect environmental health and natural resources. “Shanks said.

NIST SRM 2917 Currently available at NIST through the References Office, organizations wishing to purchase SRM can access the following sites: NISTSRM web page..

https://www.nist.gov/news-events/news/2022/04/nist-collaborates-epa-develop-standard-improve-fecal-pollution-measurements NIST is working with the EPA to develop standards for improving fecal contamination measurements in recreational waters.

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