Comparison of genotypes of extended-spectrum betalactamases producing Escherichia coli from human and environmental samplesMarič, Leon (Avtor) Janežič, Sandra (Mentor) Rupnik, Maja (Komentor) E. coliAMROne healthenvironmentepidemiologyExtended-spectrum betalactamase (ESBL)-producing Escherichia coli is recognized by the World Health Organization as one of the main priorities for the surveillance of antibiotic-resistant bacteria. Its occurrence has been well studied in human and animal reservoirs, while environmental reservoirs remain less explored. The aim of this study was to compare the genotypes of ESBL-producing E. coli between human and environmental reservoirs across three Slovenian statistical regions. Over one-year period, we collected 561 human and 564 environmental isolates. Environmental samples were obtained from water and sediment of various aquatic environments, including rivers, tributaries, lakes, gravel pits, pond, and wastewater treatment plants influents. Whole-genome sequencing was performed, and multilocus sequence typing (MLST) was used to assign sequence types at the level of housekeeping genes, while the core genome MLST (cgMLST) assessed clonality based on shared genes in core genome. In total, 196 sequence types were identified, of which 24% (representing 77% of all isolates) were present in both reservoirs. Among human isolates, ST131 (45%) and phylogroup B2 (61%) predominated, whereas sequence types among environmental isolates were more diverse and evenly distributed, encompassing phylogroups A (27%), B2 (24%), D (20%) and B1 (20%). Several clonal groups (21%) were identified, comprising isolates from human and/or environmental sources across one or more regions. Most isolates carried ESBL genes on plasmids, with blaCTX-M-15 predominating. In addition, multiple ESBL-associated plasmid replicon types (38%) were present in both human and environmental reservoirs. These results indicate a significant link between human and environmental reservoirs, with both clonal spread and plasmid-mediated transfer contributing to the dissemination of ESBL-producing E. coli.[L. Marič]20262026-06-23 13:09:11Doktorsko delo/naloga183991UDK: 579.25:579.842.1/.2:577.2VisID: 280198COBISS_ID: 282895107sl