Abstract
Objectives. Epidemiological data concerning third-generation cephalosporin (3GC) resistance in wild fauna are scarce. The aim of this study was to characterize the resistance genes, their genetic context, and clonal relatedness in 17 Escherichia coli resistant to 3GC isolated from wild animals. Methods. The isolates were characterized by short-read whole genome sequencing, and long-read sequencing was used for the hybrid assembly of plasmid sequences. Results. The 3GC resistance gene most identified in the isolates was the extended-spectrum β-lactamases (ESBL)-encoding gene blaCTX-M-1 (82.3%), followed by blaCTX-M-32 (5.9%), blaCTX-M-14 (5.9%), and blaSHV-12 (5.9%). E. coli isolates mainly belonged to the sequence types (STs) rarely reported from humans. The single nucleotide polymorphism (SNP)-based typing showed that most E. coli genomes from wild animals (wild boars, birds of prey, and buzzards) formed clonal clusters (<5 SNPs), showing a clonal dissemination crossing species boundaries. blaCTX-M-1-harboring IncI1-ST3 plasmid was the predominant ESBL-encoding plasmid (76.4%) in wild animal isolates. Plasmid comparison revealed a 110-kb self-transferable plasmid consisting of a conserved backbone and two variable regions involved in antimicrobial resistance and in interaction with recipient cells during conjugation. Conclusion. Our results highlighted the unexpected clonal dissemination of blaCTX-M-1-encoding clones and the complicity of IncI1-ST3 plasmid in the spread of blaCTX-M-1 within wild fauna.
Highlights
This study aimed to characterize a collection of 17 ESBL-producing E. coli isolates collected in distinct regions of Portugal from wild animals with different eating habits to analyze the clonal diversity of isolates and the ESBL genetic context. The results showed both an unexpected clonal dissemination of ESBL-producing E. coli and the epidemic spread of ESBL-encoding plasmids in wild fauna
It emerges from this study that the clonal dissemination of ESBL-producing E. coli strains in wild fauna crosses the species barriers
It is worth noting the moderate diversity of ESBLs detected in our E. coli isolates
Summary
Antibiotics overuse is a key factor in the emergence of antimicrobial resistance (AMR) mechanisms, especially extended-spectrum β-lactamases (ESBL) [1]. ESBLs are enzymes that confer resistance to penicillins and cephalosporins, including third-generation cephalosporins (3GC), classified by the World Health Organization (WHO) as critically important antimicrobial agents in human medicine [2]. Antimicrobial resistance is a complex and multifaceted threat to humans, animals, and the environment. Advanced knowledge on AMR has demonstrated that it affects the human sector but is widely distributed across animals and the environment [3]. A major cause of the AMR burden is the capability of AMR to transmit within and Microbiol.
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