Erste umfassende quantitative Erhebung von Antibiotikaresistenzen in vier niederösterreichischen Flüssen

Abstract

Increasing attention is being paid to the occurrence of antimicrobial resistance in surface waters and wastewater discharges. In addition to a growing number of scientific publications, the monitoring of wastewater treatment plants with a catchment area > 100,000 PE for antimicrobial resistance has also been included in the new version of the EU Urban Wastewater Treatment Directive. In order to expand the data available on the occurrence of antibiotic resistance in Austrian rivers, quantitative information on the occurrence of antimicrobial resistance in water samples from four Lower Austrian rivers was compiled for the first time. The sampling sites ranged from rather untouched river headwaters to sites downstream of wastewater treatment plants, with partly clinical wastewater in the catchment area. For a robust assessment of the antibiotic resistance status, a dual methodological approach was chosen. It considered both the occurrence of key resistance genes in the whole microbiome (the “resistome”) by direct molecular/genetic diagnostics and the frequency of phenotypic resistance (cultivation-based) in a clinically highly relevant indicator bacterium (Escherichia coli). The concentration of nine genetic antibiotic resistance markers and the phenotypic resistance of 2736 E. coli isolates to 20 antibiotics were additionally linked to modern genetic faecal markers, which also included genetic tracing of the pollution sources (microbial source tracking). Wastewater discharges had a significant influence on the antibiotic resistance situation. Phenotypic and genetic resistance values were significantly higher downstream of wastewater treatment plants, and clinically highly relevant resistance genes such as blaKPC or blaOXA48 as well as phenotypic resistance to imipenem and colistin were found at these sites. Based on these data, the study provides a first quantitative reference level of antibiotic resistance for a part of the Danube catchment area in Lower Austria. Compared to rivers in Europe and other parts of the world, the antibiotic resistance situation in the Lower Austrian rivers studied is at a low to moderate level. Nevertheless, due to the increase in heavy rainfall events caused by climate change, an increase in combined sewer overflows as well as the diffuse entry of antibiotic resistance into rivers is to be expected. At the same time, the advances in wastewater treatment and infrastructure set out in the new EU Wastewater Treatment Directive are expected to lead to a reduction in the amount of antibiotic resistance entering the environment from point sources.