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<p>The transmission of pathogenic bacteria and antimicrobial resistance genes (ARGs) between humans and livestock poses a critical public health challenge within the “One Health” framework. Here, we investigated the transmission dynamics and genomic characteristics of <i>bla</i><sub>CTX-M-</sub> and <i>bla</i><sub>NDM-</sub>positive <i>Escherichia coli</i> strains isolated from farm workers and pigs. From 1,001 fecal samples collected in Sichuan Province, China (2023), 110 <i>E. coli</i> isolates carrying <i>bla</i><sub>CTX-M</sub> and/or <i>bla</i><sub>NDM</sub> were recovered and assigned to 42 distinct sequence types (STs). Phylogenetic analysis revealed 10 intraherd transmission events; no direct evidence of cross-species transmission between humans and pigs was observed. Whole-genome sequencing revealed nine <i>bla</i><sub>CTX-M</sub> variants and three <i>bla</i><sub>NDM</sub> variants. Analysis of statistical correlations and genetic environments revealed distinct mobilization mechanisms: the dissemination of <i>bla</i><sub>CTX-M</sub> was primarily mediated by IS<i>903B</i>, IS<i>Ec9</i>, and IS<i>26</i>, whereas <i>bla</i><sub>NDM</sub> was structurally associated with IS<i>3000</i> and IS<i>26</i>, which were harbored by diverse plasmids, including IncFIB, IncY, IncHI2, and IncX3. Notably, conjugation experiments demonstrated the transferability of IncHI2 and IncX3 plasmids. The high similarity of genetic environments flanking resistance genes in human- and swine-derived isolates suggests that mobile genetic elements play a pivotal role in the horizontal transfer of these resistance determinants. Collectively, our findings indicate that the dissemination of <i>bla</i><sub>CTX-M</sub> and <i>bla</i><sub>NDM</sub> at the human–animal interface is driven primarily by horizontal gene transfer (HGT) rather than clonal expansion.</p>

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Horizontal gene transfer facilitates the dissemination of blaCTX-M and blaNDM in Escherichia coli isolates from humans and pigs in Sichuan Province, China

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月6日

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  • Luya Liu,
  • Xinyue Li,
  • Runmin Kang,
  • Yi Zhou,
  • Qin Wang,
  • Tiejun Zhang,
  • Xiaoqin Wang,
  • Xin Yang,
  • Hongning Wang,
  • Changwei Lei

摘要

The transmission of pathogenic bacteria and antimicrobial resistance genes (ARGs) between humans and livestock poses a critical public health challenge within the “One Health” framework. Here, we investigated the transmission dynamics and genomic characteristics of blaCTX-M- and blaNDM-positive Escherichia coli strains isolated from farm workers and pigs. From 1,001 fecal samples collected in Sichuan Province, China (2023), 110 E. coli isolates carrying blaCTX-M and/or blaNDM were recovered and assigned to 42 distinct sequence types (STs). Phylogenetic analysis revealed 10 intraherd transmission events; no direct evidence of cross-species transmission between humans and pigs was observed. Whole-genome sequencing revealed nine blaCTX-M variants and three blaNDM variants. Analysis of statistical correlations and genetic environments revealed distinct mobilization mechanisms: the dissemination of blaCTX-M was primarily mediated by IS903B, ISEc9, and IS26, whereas blaNDM was structurally associated with IS3000 and IS26, which were harbored by diverse plasmids, including IncFIB, IncY, IncHI2, and IncX3. Notably, conjugation experiments demonstrated the transferability of IncHI2 and IncX3 plasmids. The high similarity of genetic environments flanking resistance genes in human- and swine-derived isolates suggests that mobile genetic elements play a pivotal role in the horizontal transfer of these resistance determinants. Collectively, our findings indicate that the dissemination of blaCTX-M and blaNDM at the human–animal interface is driven primarily by horizontal gene transfer (HGT) rather than clonal expansion.