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<p>Plasmids are key vectors in the dissemination of antibiotic resistance genes. Within <i>Escherichia coli</i>, IncI1 plasmids carrying <i>bla</i><sub>CTX-M-1</sub> significantly contribute to extended-spectrum beta-lactamase (ESBL) resistance. To investigate their zoonotic dissemination potential, we compared the conjugative transfer rates, post-transfer stability, and short-term evolution of two IncI1-<i>bla</i><sub>CTX-M-1</sub> plasmids transferred from their original chicken <i>E. coli</i> host to a panel of chicken and human <i>E. coli</i> isolates. In vitro conjugation assays revealed that transfer rates were not affected by recipient host origin or temperature and were primarily governed by recipient genotype. However, post-transfer plasmid loss rates were host-dependent, with four-fold higher loss rates in human than chicken-derived transconjugants. Genomic analyses revealed substantial numbers of mutations accumulated post-acquisition, which was largely determined by the identity of the specific plasmid rather than the host origin, with both plasmids showing distinct parallel deletions in chicken and human-derived transconjugants. Specifically, the loss of genes associated with plasmid stability was observed more frequently in human than in chicken strains, while the loss of part of the conjugation machinery was observed in transconjugants from both hosts. These findings suggest that, although these plasmids transfer easily between bacteria from chicken to human isolates, they are less stable in their new host environment, which may restrict their overall spread. A comprehensive One Health risk assessment must consider these critical downstream dynamics of plasmid stability and host-specific evolution.</p>

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Post-transfer instability, not initial transfer, limits dissemination of IncI1-blaCTX-M-1 plasmids between chicken and human Escherichia coli

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年8月4日

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  • M. Buffoni,
  • E. A. J. Fischer,
  • J. DelaFuente,
  • A. San Millan,
  • A. C. Schürch,
  • R. J. L. Willems,
  • J. A. G. M. de Visser

摘要

Plasmids are key vectors in the dissemination of antibiotic resistance genes. Within Escherichia coli, IncI1 plasmids carrying blaCTX-M-1 significantly contribute to extended-spectrum beta-lactamase (ESBL) resistance. To investigate their zoonotic dissemination potential, we compared the conjugative transfer rates, post-transfer stability, and short-term evolution of two IncI1-blaCTX-M-1 plasmids transferred from their original chicken E. coli host to a panel of chicken and human E. coli isolates. In vitro conjugation assays revealed that transfer rates were not affected by recipient host origin or temperature and were primarily governed by recipient genotype. However, post-transfer plasmid loss rates were host-dependent, with four-fold higher loss rates in human than chicken-derived transconjugants. Genomic analyses revealed substantial numbers of mutations accumulated post-acquisition, which was largely determined by the identity of the specific plasmid rather than the host origin, with both plasmids showing distinct parallel deletions in chicken and human-derived transconjugants. Specifically, the loss of genes associated with plasmid stability was observed more frequently in human than in chicken strains, while the loss of part of the conjugation machinery was observed in transconjugants from both hosts. These findings suggest that, although these plasmids transfer easily between bacteria from chicken to human isolates, they are less stable in their new host environment, which may restrict their overall spread. A comprehensive One Health risk assessment must consider these critical downstream dynamics of plasmid stability and host-specific evolution.