This work monitored the effect of a municipal and a village wastewater treatment plant (WWTP) technology on the fate of beta-lactam resistance genes in bacterial populations in different phases of the wastewater treatment process. In case of the municipal WWTP1, the bacteria possessing a high ampicillin resistance (minimal inhibitory concentration (MIC) values of 20 mg/mL) accumulated in the sedimentation tank, which was accompanied with a higher concentration of ampicillin in the wastewater samples (28.09 ng/L) and an increase in the relative abundance of the blaTEM gene in the bacterial population. However, an opposite trend was revealed with the blaNDM-1 gene, making the sedimentation processes of WWTP1 crucial only for the accumulation of the blaTEM gene. Similarly, the comparison with the WWTP2 showed that the accumulation of the ampicillin resistance in bacterial population probably depended on the WWTP technology and wastewater composition. Out of the four tested resistance genes (blaTEM, blaKPC, blaNDM-1, and blaOXA-48), blaTEM and blaNDM-1 genes were the only two detected in this study. According to NGS analysis of bacterial 16 S rRNA gene, Gammaproteobacteria dominated the ampicillin-resistant bacteria of the WWTP sedimentation tanks. Their relative abundance in the bacterial population also increased during the sedimentation processes in WWTP1. It could indicate the role of the bacterial taxon in ampicillin resistance accumulation in this WWTP and show that only 9.29% of the original bacterial population from the nitrification tank is involved in the documented shifts in beta-lactam resistance of the bacterial population.

Department of Biology and Ecology Faculty of Science University of Ostrava Chittussiho 10 CZ 710 00 Ostrava Czech Republic

Institute of Medical Biochemistry and Laboratory Diagnostics Clinical Microbiology and ATB Center General University Hospital Prague U Nemocnice 2 CZ 128 08 Prague Czech Republic

Institute of Microbiology of the Czech Academy of Sciences Vídeňská 1083 CZ 142 20 Prague Czech Republic; Institute for Environmental Studies Faculty of Science Charles University Benátská 2 CZ 128 01 Prague Czech Republic

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Resistant Genes and Multidrug-Resistant Bacteria in Wastewater: A Study of Their Transfer to the Water Reservoir in the Czech Republic