A new study from Chicago-based researchers has found that a confluence of sewage overflows and widespread antibiotic use is causing the proliferation of antibiotic-resistant bacteria in waterways around the Windy City.
Recently published in the journal Environmental Science and Technology, the study looked at the antibiotic triclosan, which is in about half of liquid soaps and functions by slowing or stopping the growth of bacteria, fungi, and mildew. Triclosan frequently gets into streams and rivers through domestic waste-water, leaky sewers and sewage overflows.
“The bacterial resistance caused by triclosan has real environmental consequences,” said study author Emma Rosi-Marshall, an aquatic ecologist at the Cary Institute of Ecosystem Studies in Millbrook, New York. “Not only does it disrupt aquatic life by changing native bacterial communities, but it’s linked to the rise of resistant bacteria that could diminish the usefulness of important antibiotics.”
In the study, researchers collected samples at three sites in the Greater Chicago area: the urban North Shore Channel, the suburban West Branch Dupage River, and the rural Nippersink Creek. The team found a correlation between urbanization and a rise in both triclosan concentrations in sediments and the ratio of bottom-dwelling bacteria resistant to the antibiotic. The rural creek had the lowest levels of triclosan-resistant bacteria, while the urban site sampled downstream of 25 combined sewer overflows had the highest levels.