TY - CONF A1 - Schulz, Anne-Christine A1 - Schreiber, Frank T1 - Assessing co-selection of biocide and antibiotic resistance in wastewater microbial communities N2 - Biocides are used for a wide range of purposes, including disinfectants or preservatives. Biocides play a major role in the prevention of microbial infections in healthcare and animal husbandry. The use of biocides often leads to the discharge of active biocidal substances into wastewater streams, causing the exposure of wastewater microbial communities to subinhibitory concentrations. In turn, it is known that wastewater treatment plants (WWTP) are hotspots for antibiotic resistant bacteria. Since similar mechanisms confer resistance to biocides and antibiotics, exposure to biocides can result in co-selection of antibiotic resistant bacteria in WWTP due to biocides. Here, we investigate the magnitude and the drivers of co-selection of antibiotic resistance in natural wastewater microbial communities upon biocide exposure. Microbial communities will be sampled at the WWTP Ruhleben in Berlin and characterized regarding their biocide and antibiotic resistance. Changes in the resistance level after exposure to different biocides will be determined by enumerating resistant and non-resistant E. coli and heterotrophic bacteria on selective plates with and without several biocides and antibiotics. Moreover, we are establishing a synthetic community comprising about 100 environmental E. coli isolates each with different antimicrobial resistance traits. Each isolate will be tagged with a unique DNA-barcode. All isolates will be pooled and exposed to different biocides at various concentrations. The barcode labeling enables us to determine the abundance of each isolate at the beginning and end of the experiment by transposon-tag sequencing. The project results will inform risk assessment of the effects of biocidal residues on antimicrobial resistance selection in WWTP. The project is part of the BIOCIDE consortium funded within the call on Aquatic pollutants by JPI-AMR, JPI-OCEANS and JPI-WATER. T2 - 6th International Symposium onn the Environmental Dimension of Antibiotic Resistance - EDAR 6 CY - Gothenburg, Sweden DA - 22.09.2022 KW - Antibiotic resisitance KW - Biocide KW - Wastewater KW - Risk assesment PY - 2022 AN - OPUS4-56796 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schulz, Anne-Christine A1 - Schreiber, Frank T1 - Co-selection for biocide and antibiotic resistance in microbial wastewater communities N2 - Biocides are used for a wide range of purposes, including disinfectants or preservatives. They play a major role in the prevention of microbial infections in healthcare and animal husbandry. The use of biocides often leads to the discharge of active biocidal substances into wastewater streams, causing the exposure of wastewater microbial communities to subinhibitory concentrations. In turn, it is known that wastewater treatment plants (WWTP) are hotspots for antibiotic resistant bacteria. Since similar mechanisms confer resistance to biocides and antibiotics, exposure to biocides can result in co-selection of antibiotic resistant bacteria in WWTP Here, we want to investigate co-selection processes of antibiotic resistance in natural WWTP microbial communities upon biocide exposure. Microbial communities were sampled at the WWTP Ruhleben in Berlin and characterized regarding their susceptibility against different clinically relevant antibiotics. To investigate the link between biocide exposure and antibiotic resistance, changes in the susceptibility level after exposure to environmentally relevant concentrations of the commonly used biocide didecyldimethylammonium chloride (DDAC) will be determined by enumerating resistant and non-resistant E. coli on selective plates with and without antibiotics and DDAC. In case of antibiotics, clinical breakpoint concentrations according to EUCAST will be used to discriminate between susceptible and resistant strains. In case of DDAC (and biocides in general), clinical breakpoints do not exist. Therefore, we determined a cut-off concentration at which the majority of naturally-occurring E. coli strains cannot grow anymore based on (I) the MIC (minimal inhibitory concentration) distribution, and (II) by plating wastewater communities onto selective indicator agar plates loaded with increasing DDAC concentration. Additionally, antibiotic cross-resistance will be determined by spotting single colonies, isolated from DDAC-selective plates onto antibiotic plates. The results of our experiments will help to determine selective concentrations and to estimate the risk of antibiotic co-selection and cross-resistance in microbial WWTP communities upon biocide exposure. T2 - Annual Conference 2023 of the Association for General and Applied Microbiology CY - Göttingen, Germany DA - 10.09.2023 KW - Antibiotic resisitance KW - Biocide KW - Wastewater KW - Risk assesment PY - 2023 AN - OPUS4-58510 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -