Abstract
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 blaCTX-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.
Highlights
Antibiotic resistance in bacteria is an emerging problem globally
Two ESBL E. coli PhP types were repeatedly found in wastewater from an urban community in Norway
The metal tolerance did not increase in the isolates collected later in the study. These results indicate that ST648 and sequence type 131 (ST131) in this study are tolerant to copper at a level comparable to the control strains and, while slightly more tolerant to zinc than the controls, the levels in the wastewater are probably not high enough to confer any selective pressure that explains the repeated findings of these sequence types (STs) in the wastewater pump station
Summary
Antibiotic resistance in bacteria is an emerging problem globally. Resistant bacteria are found in human and animal microbiota, as well as in the environment. The emergence of antibiotic resistance, especially E. coli strains producing extended-spectrum -lactamases (ESBLs), has complicated the medical treatment of ExPEC infections [10]. ESBL-producing E. coli sequence type 131 (ST131) is a globally distributed uropathogenic E. coli (UPEC) lineage with higher virulence capacity and antibiotic resistance than other ExPEC clones, which might explain its high occurrence and persistence in urinary and bloodstream infections [10, 13]. The global dissemination of E. coli ST131 has been largely related to the pandemic emergence of the CTX-M-15 group of ESBL enzymes [14]. E. coli ST131 and ST648 producing CTX-M have been reported worldwide, in human infections and in animal samples [13]. CTX-M-producing enterobacteria, including E. coli, are causing highly antibiotic-resistant infections that are difficult to treat [11, 12]
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