Fecal pollution routes of antibiotic resistance in rivers

The increase in antimicrobial resistances is a global threat to human and animal health. Every year in the European Union alone, an estimated 25,000 patients die because of a serious resistant bacterial infection acquired in hospitals. Outside of hospitals, the spread of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARG) via wastewater discharge into aquatic ecosystems are of growing importance, affecting humans and animals via drinking water production, irrigation, watering or bathing, especially in large river systems where many people are concerned. In this project, the River Danube - the second longest river in Europe and most international river in the world - shall be investigated along its whole length, as well as its most important tributaries to assess the major sources, propagation pathways and driving factors influencing the occurrence and spreading of ARB and ARG. A new holistic and quantitative concept will be applied to test the following hypotheses: (i) In the water compartment, the abundance of ARB and ARG is coupled to the extent of fecal pollution and further depends on their persistence in the environment and the hydrological conditions. (ii) In biofilms and fine sediments, ARB and ARG abundance are uncoupled from the extent of fecal pollution. Accumulation of ARB and ARG occurs, dependent on specific ecological selection factors and qualitative changes of the fecal pollution input (untreated vs treated wastewater, different antibiotic use patterns in different countries). (iii) The patterns of ARB and ARG abundance may be extremely different even between closely related species and using only one bacterial target leads to a biased image of the occurrence and spread of antibiotic resistances in aquatic environments. The new concept is based on the quantification of ARB and ARG in multiple bacterial targets, determined in the water and biofilm compartment by a combination of cultivation and genetic approaches. This information will be combined with quantitative data on the extent and sources of fecal pollution and with a comprehensive assessment of the environmental conditions, performed during the Joint Danube Survey (JDS), the worlds biggest river research expedition. This river survey will be followed by a one-year survey at selected critical sites. So far, ARB and ARG distribution in aquatic environments has been investigated only at small scales considering a relatively low number of environmental parameters. The proposed quantitative whole- river approach will provide for the first time a comprehensive picture of the main factors driving ARB and ARG occurrence and spreading along the total length of a large river in an international context. This will promote new ideas and possibilities to understand and manage microbial water quality and antibiotic resistance at large rivers.

A press release was launched in May 2024 concerning the occurrence and spread of Antimicrobial Resistance in the Danube River, in relation to the publication Schachner-Groehs et al 2024 (Water Research 252: 121144). At the national and international level, there was a broad response to this release with requests for interview by public radio (ORF, Ö1), newspapers (Der Standard, Die Tageszeitung) and publications ins newspapers and on-line media.