Dissecting the clonality of I1 plasmids using ORF-based binarized structure network analysis of plasmids (OSNAp)

We aimed to elucidate the relationship among blaCTX-M-carrying plasmids and their transmission between humans and domestic animals. Phylogenetic relationship of 90 I1 plasmids harboring blaCTX-M genes encoding extended-spectrum β-lactamase (ESBL) was analyzed using the ORF-based binarized structure network analysis of plasmids (OSNAp). The majority of plasmids carrying blaCTX-M-1 or blaCTX-M-8 belonged to a single lineage, respectively, and were primarily associated with domestic animals especially chickens. On the other hand, plasmids carrying blaCTX-M-14 or blaCTX-M-15, identified from both humans and domestic animals, were distributed in two or more lineages. OSNAp has revealed the phylogenetic relationships and diversity of plasmids carrying blaCTX-M more distinctly than pMLST. The findings suggest that circulation of I1 plasmids between humans and animals may contribute to their diversity.