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Antimicrob Agents Chemother. 2019 Aug 23;63(9). pii: e00823-19. doi: 10.1128/AAC.00823-19. Print 2019 Sep.

Repeated Isolation of Extended-Spectrum-β-Lactamase-Positive Escherichia coli Sequence Types 648 and 131 from Community Wastewater Indicates that Sewage Systems Are Important Sources of Emerging Clones of Antibiotic-Resistant Bacteria.

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Department of Food Safety and Infection Biology, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Solna, Sweden.
Department of Infectious Diseases, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Solna, Sweden


Antibiotic resistance in bacteria is an emerging problem globally. Resistant bacteria are found in human and animal microbiota, as well as in the environment. Wastewater receives bacteria from all these sources and thus can provide a measurement of abundance and diversity of antibiotic-resistant bacteria circulating in communities. In this study, water samples were collected from a wastewater pump station in a Norwegian suburban community over a period of 15 months. A total of 45 daily samples were cultured and analyzed for the presence of Escherichia coli Eighty E. coli-like colonies were collected from each daily sample and then phenotyped and analyzed for antibiotic resistance using the PhenePlate-AREB system. During the sampling period, two unique E. coli phenotypes with resistance to cefotaxime and cefpodoxime indicating carriage of extended-spectrum β-lactamases (ESBL) were observed repeatedly. Whole-genome sequencing of 15 representative isolates from the two phenotypes identified these as two distinct clones belonging to the two globally spread E. coli multilocus sequence types (STs) ST131 and ST648 and carrying bla CTX-M-15 The number of ESBL-positive E. coli strains in the community wastewater pump station was 314 of 3,123 (10%) analyzed E. coli strains. Of the ESBL-positive isolates, 37% belonged to ST648, and 7% belonged to ST131. Repeated findings of CTX-M-15-positive ST648 and ST131 over time indicate that these STs are resident in the analyzed wastewater systems and/or circulate abundantly in the community.


ESBL E. coli ; Norway; ST131; ST648; antibiotic resistance; antibiotic surveillance; persistence; sewage; wastewater; whole-genome sequencing

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