The investigation of antibiotic residues, antibiotic resistance genes and antibiotic-resistant organisms in a drinking water reservoir system in Germany.

Between August 2018 and June 2019, a river system in Germany that supplies a drinking water reservoir and is subject to the discharge from two sewage treatment plants was monitored for antibiotic residues via liquid chromatography-tandem mass spectrometry, antibiotic resistance genes (including blaNDM, blaVIM, blaOXA-48, blaKPC, blaGIM, blaSME, blaIMI, blaIMP, blaSPM, blaSIM, blaOXA-23, blaOXA-24, blaOXA-51, blaOXA-58, mcr) via qualitative real-time PCR and antibiotic-resistant bacteria [belonging to the ESKAPE-group (Enterococcus faecium, Staphyhlococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter ssp.; with resistance against Carbapenemases, Cephalosporines and Colistin) and Escherichia coli] based on cultivation methods followed by a characterization via MALDI-TOF MS and susceptibility testing applying microdilution. Residues of macrolide antibiotics such as clarithromycin (up to 0.60 µg/L) and residues of sulfamethoxazole (up to 0.40 µg/L) and trimethoprim (up to 0.39 µg/L) were detected downstream of the sewage treatment plants. In addition, no antibiotic residues were detected upstream the respective sewage treatment plants, except for anhydroerythromycin (n = 1,