For nearly a century, scientists have been waging war against antibiotic-resistant microbes. Researchers at Michigan State University say they’ve found a new way to prevent this: by releasing “DNA traps” into wastewater treatment plants.
Syed Hashsham, MSU professor of civil and environmental engineering, and James Tiedje, professor emeritus at the university in the Departments of Plant, Soil and Microbial Sciences, as well as Microbiology and Molecular Genetics, have found an enzyme that breaks down floating strands of antibiotic-resistant DNA in wastewater before bacteria can pick them up and take on their antibiotic-resistant properties.
Hashsham said this could be a powerful, environmentally friendly tool to control the spread of antibiotic resistance in wastewater and keep antibiotics effective.
The two MSU researchers published their findings in Natural water on August 19, together with lecturers from the University of Science and Technology of China. Hashsham plans to continue testing the enzyme and exploring its use as a wastewater disinfectant.
“As with any new discovery, more work needs to be done to optimize the technology,” Hashsham said. “But it really is a very new technique.”
Antibiotic resistance has plagued modern medicine since the invention of penicillin, largely due to misuse and overprescribing. Bacteria are constantly evolving and trying to survive as new antibiotics come onto the market. Each new antibiotic only takes five to eight years for bacteria to adapt, making infections difficult to treat, Hashsham said. This technology could help maintain the effectiveness of current antibiotics
Although doctors are more careful about prescribing antibiotics these days, scientists are also working to prevent the spread of antibiotic-resistant microbes. A hotspot for antibiotic-resistant microbes is in wastewater treatment plants, because infected people release the bacteria in their feces.
Mobile genetic elements carrying antibiotic-resistant genes are also found in wastewater. When picked up by pathogenic bacteria, they inherit the antibiotic resistance gene.
Researchers came up with the idea of ​​using a so-called restriction enzyme. These enzymes work like scissors and cut genetic material into so many pieces that they are useless. They are well known in molecular biology, but have not yet been used in antibiotic resistance.
The researchers cultivated the bacterium Shewanella oneidensis to produce an enzyme called nuclease, or what they call a “DNA scavenger.” This treatment would be economically feasible for wastewater treatment plants, without negatively interacting with the other chemicals already added for wastewater disinfection.
As a DNA cleanup crew, they added the enzyme to the wastewater in concentrated, targeted amounts. Within four hours, almost all four types of mobile genetic elements were destroyed. Within six hours they were completely inactivated.
“More research with larger scale systems and more complex wastewater matrices is needed for this discovery to be optimized, compatible with existing disinfection practices and cost-effective,” Hashsham said.
The next step is to continue testing the effectiveness of the DNA scavenger on other mobile genetic elements. Some researchers think the enzyme could be an alternative to chlorine or other disinfectants in wastewater. Although Hashsham is not ready to recommend it, he is confident that this technique can be a useful tool in the fight against antibiotic resistance.
