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Background <p>The emergence of <i>tmexCD-toprJ</i>, a plasmid-mediated resistance-nodulation-division efflux pump gene cluster conferring resistance to tigecycline, poses a critical public health threat. While its prevalence among adults and within hospital settings has been extensively studied, its occurrence and epidemiological characteristics in pediatric populations remains scarcely reported and largely unknown.</p> Results <p>In this study, a total of 2,344 clinical <i>Klebsiella</i> isolates collected from pediatric patients (2019–2025) were screened for <i>tmexCD-toprJ</i> using PCR, and five positive isolates were identified. Antibiotic susceptibility via broth microdilution confirmed that all five isolates were multidrug-resistant, including one isolate resistant to almost all tested antimicrobial classes. Whole-genome sequencing and bioinformatics analysis were conducted to determine their genetic contexts. These strains were assigned to four distinct sequence types (STs): ST15, ST571, ST750-1LV, and ST3520-1LV, and exhibited diverse capsular locus types. Beyond <i>tmexCD-toprJ</i>, the five isolates also harbored carbapenemase genes (<i>bla</i><sub>NDM−1</sub>, <i>bla</i><sub>NDM−5</sub>, <i>bla</i><sub>IMP−4</sub>, and <i>bla</i><sub>OXA−1</sub>) and other antimicrobial resistance genes. The <i>tmexCD-toprJ</i> gene cluster was located on plasmids belonging to various incompatibility groups, including IncHI1B/IncFIB/IncR/IncN, IncHI1B/IncFIB, IncX3, and IncHI1B/IncFIB (Mar). However, conjugation assays demonstrated that these <i>tmexCD-toprJ</i>-carrying plasmids were non-transferable to the <i>Escherichia coli</i> recipients under the tested conditions.</p> Conclusions <p>Taken together, this study reports the concerning co-harboring of <i>tmexCD-toprJ</i> with carbapenemase genes and other resistance determinants in <i>Klebsiella</i> spp. isolates recovered from pediatric patients in China. The presence of these resistance mechanisms on diverse genomic backgrounds highlights a significant clinical risk and underscores the urgent need for enhanced genomic surveillance and targeted strategies to preserve tigecycline efficacy in children.</p>

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Characterization of tmexCD-toprJ-positive Klebsiella spp. from pediatric patients in a Chinese hospital

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月23日

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  • Chang Jiang,
  • Xiangkun Zeng,
  • Xinyu Zhang,
  • Lili Huang,
  • Lei Liu,
  • Xiaofan Li,
  • Ying Liu,
  • Ning Dong,
  • Shengwei Zhang,
  • Yuanyuan Li

摘要

Background

The emergence of tmexCD-toprJ, a plasmid-mediated resistance-nodulation-division efflux pump gene cluster conferring resistance to tigecycline, poses a critical public health threat. While its prevalence among adults and within hospital settings has been extensively studied, its occurrence and epidemiological characteristics in pediatric populations remains scarcely reported and largely unknown.

Results

In this study, a total of 2,344 clinical Klebsiella isolates collected from pediatric patients (2019–2025) were screened for tmexCD-toprJ using PCR, and five positive isolates were identified. Antibiotic susceptibility via broth microdilution confirmed that all five isolates were multidrug-resistant, including one isolate resistant to almost all tested antimicrobial classes. Whole-genome sequencing and bioinformatics analysis were conducted to determine their genetic contexts. These strains were assigned to four distinct sequence types (STs): ST15, ST571, ST750-1LV, and ST3520-1LV, and exhibited diverse capsular locus types. Beyond tmexCD-toprJ, the five isolates also harbored carbapenemase genes (blaNDM−1, blaNDM−5, blaIMP−4, and blaOXA−1) and other antimicrobial resistance genes. The tmexCD-toprJ gene cluster was located on plasmids belonging to various incompatibility groups, including IncHI1B/IncFIB/IncR/IncN, IncHI1B/IncFIB, IncX3, and IncHI1B/IncFIB (Mar). However, conjugation assays demonstrated that these tmexCD-toprJ-carrying plasmids were non-transferable to the Escherichia coli recipients under the tested conditions.

Conclusions

Taken together, this study reports the concerning co-harboring of tmexCD-toprJ with carbapenemase genes and other resistance determinants in Klebsiella spp. isolates recovered from pediatric patients in China. The presence of these resistance mechanisms on diverse genomic backgrounds highlights a significant clinical risk and underscores the urgent need for enhanced genomic surveillance and targeted strategies to preserve tigecycline efficacy in children.