Integration of blaOXA-48 into a Col156 plasmid drove a carbapenem-resistant Escherichia coli ST131 outbreak in New Zealand: Global genomic evidence for the gene’s multilayered dissemination

Structured Abstract Aims To investigate the genetic diversity in OXA-48-producing Escherichia coli ST131 in a New Zealand community outbreak, and to characterize the mobile genetic elements carrying bla OXA-48 , with emphasis on the gene’s global dissemination. Methods Forty outbreak isolates underwent short-read sequencing; 36 also underwent long-read sequencing. Bayesian phylogenetics reconstructed the emergence and spread of the outbreak. A pangenome graph of 543 Col156 plasmids and 806 global bla OXA-48 -positive contigs were analyzed to assess structural diversity, mobility, and global distribution. Results The outbreak clone likely emerged circa 2017, following a single introduction into New Zealand after acquiring bla OXA-48 on a 7,872 bp Col156 plasmid. It shares ancestry (circa 2009) with Southeast Asian E. coli ST131 genomes. Long-read sequencing and pangenome graph analyses identified a single IS 1 -mediated transposition of bla OXA-48 into a Col156 plasmid backbone, observed across species and continents. Globally, bla OXA-48 is present in diverse plasmid contexts and insertion sequence arrangements and is widely distributed among Enterobacterales. Conclusions This is the first high-resolution genomic reconstruction of a community-associated bla OXA-48 outbreak, identifying a compact Col156 plasmid as a key vector driving carbapenem resistance. Our findings demonstrate the value of complete genome assemblies and pangenome graph analyses in resolving the structural and evolutionary dynamics of antimicrobial resistance.