Antibiotic resistance genes – a growing health problem around the world – are present in water systems in northern Colorado and should be viewed more seriously as contaminants by the scientific community, a Colorado State University civil engineering professor urges in an upcoming issue of the American Chemical Society’s Environmental Science and Technology journal.
Amy Pruden, an assistant professor of civil and environmental engineering, and her team looked for the occurrence of tetracycline and sulfonamide antibiotic resistance genes in five sampling sites along the Poudre River. As expected, they found higher concentrations in more populated or heavily farmed areas, but still detected antibiotic resistance genes in all sampling areas.
Tetracycline and sulfonamide are commonly used antibiotics in people and animals.
Pruden found that treated water and wastewater also carried the genes.
"Microbes carrying these antibiotic resistance genes are not effectively killed by antibiotics, and the presence of these drugs in the environment may stimulate them to proliferate," Pruden said.
Pruden co-authored the paper with Ken Carlson, a civil engineering professor, and two graduate students, Ruoting Pei and Heather Storteboom. Funding for the research was provided through a $400,000, five-year CAREER grant awarded this year from the National Science Foundation and from the U.S. Department of Agriculture NRI Watersheds program and the USDA Agricultural Experiment Station at Colorado State.
Pruden notes that even if cells carrying the genes have been killed, the DNA still winds up in the environment and may get transferred to other cells. She stressed that testing so far only covers two classes of antibiotic resistance genes – others may also be present in the environment and have varied responses to environmental conditions.
"Antibiotic resistance genes in and of themselves can be considered to be emerging ‘contaminants’ for which mitigation strategies are needed to prevent their widespread dissemination," Pruden said. "This is especially true as the rate of discovery and development of new antibiotics is continually declining while the corresponding development and spread of resistance is occurring at a rapid pace."
More than 2 million Americans are infected each year with resistant pathogens; 14,000 die, according to the World Health Organization. The WHO considers antibiotic resistance to be one of the most pressing health challenges of the next century.
"This is a new class of contaminant that can have a measurable impact on human and environmental health," Pruden said. "I want to know how they’re spread and develop models and find out how to treat them."
The next step of her research is to follow the path of the genes through the watershed and more closely identify the sources. At the same time, she will investigate basic modifications to water treatment to destroy the genes’ DNA.
"We have some evidence of how they spread in the environment, but we need to study it in more detail to confirm the pathways," she said. "Where is it coming from, where does it end up, how does it get there?
"With environmental problems, it’s often when you reach a point of no return that people start thinking about doing something," she said. "We’re hoping to avoid that."
Pruden is teaching an experimental course in molecular biology for engineers this fall. The course is now a permanent part of the engineering curriculum and will help equip engineering students to tackle complex bioenvironmental problems.
She is also working with Carlson to test an early-warning security system designed to alert city utility officials when major pollutants are detected in water supplies. If installed, the real-time monitoring system, integrated by ST-Infonox of California, would help city officials respond quickly to foreign substances in the water distribution system, helping to combat any potential terrorist or natural threats.
ST-Infonox officials are working with city officials in Loveland and Fort Collins to test the technology on municipal water systems.
Pruden joined Colorado State University in 2002. She obtained her bachelor’s and her doctoral degree from the University of Cincinnati.