Genomic analysis reveals close genetic similarity between ESBL and other β-lactamase-producing E. coli isolates from humans and dogs, suggesting potential for inter-species transmission

Extended-spectrum β-lactamase-(ESBL)-producing Enterobacteriaceae are emerging in hospital and community settings as important causes of urinary tract infections. These plasmid-mediated enzymes have been identified in human and dog hosts, with bla CTX−M variants being the most prevalent ESBLs worldwide. Our objective was to identify horizontal gene transfer (HGT) events amongst human and dog-derived ESBL-producing bacteria by examining genetic relatedness of plasmid and bacterial whole genome sequences (WGS) associated with ESBLs and other β-lactamase genes. By understanding genetic relatedness, we aimed to provide insight into transmission dynamics of ESBLs and antibiotic resistance among humans and dogs in community-acquired settings. Of 149 plasmids collected from humans ( n = 125) and dogs ( n = 24), 111 (74.5%) carried class A ESBL genes with bla CTX−M−14 (31.6%) predominating in human-derived plasmids and bla CTX−M−1 in dog-derived plasmids (29.6%). In addition, ESBLs and other β-lactamase genes, including bla TEM−1 ,were also identified in both populations. pMLST showed that IncF, IncI1, and IncN plasmids were the main groups contributing to the dissemination of ESBLs amongst human and dog populations. Neighbor-joining analysis revealed clustering of human and dog-derived plasmids carrying similar ESBL genes as well as other antibiotic-resistant genes. The maximum-likelihood tree revealed a high predominance of ST131 carried by E. coli serotypes O25:H4 in humans but not dogs. Virulence gene analysis revealed that ESBL-producing bacteria were not limited to UPEC. The presence of conserved ESBLs, other β-lactamase genes and E. coli clones in both humans and dogs highlights widespread circulation of shared resistance elements. These findings support the need for broader One Health surveillance, particularly involving companion animals, to better track and mitigate ARG spread in community settings.