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Background <p>We investigated a KPC-2-producing Enterobacterales (KPC-2 CPE) outbreak in a Korean hospital from July to September 2019, which subsided following enhanced surveillance and strict infection control. The study aimed to elucidate transmission dynamics using epidemiological and genomic methods.</p> Methods <p>The study period covered the outbreak and a 9-month post-outbreak observation. Investigations included a matched case-control study and whole-genome sequencing (WGS) of isolates, including long-read sequencing for two isolates. Single nucleotide polymorphism (SNP) analysis (≤ 6 SNPs for clonality, ≤ 15 for relatedness) was used to construct transmission networks.</p> Results <p>A total of 42 KPC-2 CPE cases were identified: 34 <i>Klebsiella pneumoniae</i>, 4 <i>Escherichia coli</i>, 1 <i>Enterobacter asburiae</i>, and 3 cases co-colonized with <i>K. pneumoniae</i> and <i>E. coli</i>. Among these, 33 were hospital-linked and 9 were imported. Retrospective tracing indicated that covert transmission began a month before the outbreak, and 13 hospital wards were identified as potential acquisition sites. Genomic analysis revealed all but one <i>K. pneumoniae</i> belonged to ST307, cgMLST 439, which grouped into three clades. Clade 1 was linked to a specific hospital ward, supported by the case-control study (adjusted odds ratio, 3.63; 95% confidence interval, 1.36–9.63); Clade 2 was spread between wards via a haemodialysis unit and shared healthcare personnel. Imported cases had the same clones as early hospital-linked cases, suggesting undetected introduction before enhanced surveillance. Additionally, an IncX3 plasmid carrying <i>bla</i><sub>KPC-2</sub> was found in both <i>K. pneumoniae</i> and <i>E. coli</i>, indicating horizontal gene transfer.</p> Conclusion <p>This study demonstrates that clonal spread of KPC-2 CPE can remain undetected without enhanced active surveillance, underscoring the need for early detection. Genomic analysis clarified ST307 <i>K. pneumoniae</i> transmission through unrecognised epidemiological links and horizontal <i>bla</i><sub>KPC-2</sub> transfer to <i>E. coli</i>.</p>

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Outbreak investigation and genomic analysis reveal hidden transmission networks of KPC-2-producing Enterobacterales in a South Korean hospital

  • 期刊论文

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  • 发表日期：

    2026年2月7日

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  • Sun Hee Park,
  • Seul Ki Ji,
  • Soyoung Shin,
  • Chulmin Park,
  • Jeong-Ih Shin,
  • Seung-Hyun Jung,
  • Jung-Hyun Choi,
  • Dong-Gun Lee

摘要

Background

We investigated a KPC-2-producing Enterobacterales (KPC-2 CPE) outbreak in a Korean hospital from July to September 2019, which subsided following enhanced surveillance and strict infection control. The study aimed to elucidate transmission dynamics using epidemiological and genomic methods.

Methods

The study period covered the outbreak and a 9-month post-outbreak observation. Investigations included a matched case-control study and whole-genome sequencing (WGS) of isolates, including long-read sequencing for two isolates. Single nucleotide polymorphism (SNP) analysis (≤ 6 SNPs for clonality, ≤ 15 for relatedness) was used to construct transmission networks.

Results

A total of 42 KPC-2 CPE cases were identified: 34 Klebsiella pneumoniae, 4 Escherichia coli, 1 Enterobacter asburiae, and 3 cases co-colonized with K. pneumoniae and E. coli. Among these, 33 were hospital-linked and 9 were imported. Retrospective tracing indicated that covert transmission began a month before the outbreak, and 13 hospital wards were identified as potential acquisition sites. Genomic analysis revealed all but one K. pneumoniae belonged to ST307, cgMLST 439, which grouped into three clades. Clade 1 was linked to a specific hospital ward, supported by the case-control study (adjusted odds ratio, 3.63; 95% confidence interval, 1.36–9.63); Clade 2 was spread between wards via a haemodialysis unit and shared healthcare personnel. Imported cases had the same clones as early hospital-linked cases, suggesting undetected introduction before enhanced surveillance. Additionally, an IncX3 plasmid carrying blaKPC-2 was found in both K. pneumoniae and E. coli, indicating horizontal gene transfer.

Conclusion

This study demonstrates that clonal spread of KPC-2 CPE can remain undetected without enhanced active surveillance, underscoring the need for early detection. Genomic analysis clarified ST307 K. pneumoniae transmission through unrecognised epidemiological links and horizontal blaKPC-2 transfer to E. coli.