Contaminated waste water often flows into rivers and streams after heavy rains. Antibiotic-resistant bacteria thus also enter the waters. Eawag is researching exactly which ones and in what amounts as part of a national research programme.
Waste water treatment facilities are often overwhelmed by heavy rains and a part of the waste water reaches the water system untreated. Helmut Bürgmann and a group of researchers from the Eawag Federal Institute of Aquatic Science and Technology are investigating how such events influence the amount and composition of antibiotic-resistant bacteria in the water system as part of National Research Project (NRP) 72 “Antimicrobial Resistance”.
Sampling during heavy rains
He and doctoral student Jangwoo Lee have taken water samples from nine bodies of water both upstream and downstream of waste water treatment facilities, during and after heavy rains. Genetic anaylses and flow cytometric measurements determined the amount and type of bacteria and antibiotic resistances in the samples.
It is known that antibiotic-resistant bacteria enter the water not only from waste water plants, but also diffusely from agricultural areas. The first results from the project now show the contribution of each source and how this changes with heavy rain: “The proportion of antibiotic-resistant bacteria downstream of the waste water treatment facilities increases strongly during and after heavy rain,” says Jangwoo Lee. Detailed analyses are still ongoing and will be published during the year.