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<p>The concerted overexpression of multiple efflux pumps in <i>Pseudomonas aeruginosa</i> now represents a key driver of multidrug resistance (MDR), progressively undermining the efficacy of conventional antibiotic therapies. The transferability of plasmid pXM8-2 was assessed by conjugation experiments. The antimicrobial susceptibility of strains P113, P118, T117, and XM8 was determined using the BioMerieux VITEK-2 system in conjunction with the disk diffusion method. β-lactamase or carbapenemase production was detected per CLSI guidelines. Efflux pump gene expression was quantified by quantitative real-time PCR, and O-antigen serotyping was performed phenotypically with specific antisera and genotypically via bioinformatics tools. Whole-genome sequencing using Illumina and nanopore platforms revealed a comprehensive profile of antibiotic resistance genes. Phenotypically, strains P113, P118, and T117 were resistant to all antibiotics tested, consistent with their genotypes. In contrast, strain XM8, which also harbored numerous resistance genes, remained susceptible to colistin. All attempts to transfer the pXM8-2 plasmid via conjugation were unsuccessful. The studied strains exhibited a MDR phenotype, primarily conferred by the overexpression of efflux pumps (e.g., MexAB-OprM, MexCD-OprJ, MexXY, MexEF-OprN) and inactivation of the <i>oprD</i>. Genotypic characterization identified strains P113, P118, and T117 as ST11/O3 (ExoS<sup>+</sup>/ExoU<sup>−</sup>), whereas XM8 was ST385/O6 (ExoS<sup>+</sup>/ExoU<sup>−</sup>). Evolutionary analysis indicated the global dissemination of XM8-like clones, with a pronounced peak in 2023–2024. Crucially, the MDR of XM8 was further exacerbated by antibiotic resistance genes located on its non-transferable plasmid, pXM8-2. Enhanced surveillance and preemptive containment measures are urgently needed to mitigate the public health threat posed by these resistant lineages.</p>

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Genomic characterization of high-level efflux pump overexpression in Pseudomonas aeruginosa clones with epidemic potential

  • 期刊论文

  • 发表日期：

    2025年11月22日

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  • Xiyuan Lin,
  • Zherui Guo,
  • Wenji Wang,
  • Dongguo Wang,
  • Liman Ma

摘要

The concerted overexpression of multiple efflux pumps in Pseudomonas aeruginosa now represents a key driver of multidrug resistance (MDR), progressively undermining the efficacy of conventional antibiotic therapies. The transferability of plasmid pXM8-2 was assessed by conjugation experiments. The antimicrobial susceptibility of strains P113, P118, T117, and XM8 was determined using the BioMerieux VITEK-2 system in conjunction with the disk diffusion method. β-lactamase or carbapenemase production was detected per CLSI guidelines. Efflux pump gene expression was quantified by quantitative real-time PCR, and O-antigen serotyping was performed phenotypically with specific antisera and genotypically via bioinformatics tools. Whole-genome sequencing using Illumina and nanopore platforms revealed a comprehensive profile of antibiotic resistance genes. Phenotypically, strains P113, P118, and T117 were resistant to all antibiotics tested, consistent with their genotypes. In contrast, strain XM8, which also harbored numerous resistance genes, remained susceptible to colistin. All attempts to transfer the pXM8-2 plasmid via conjugation were unsuccessful. The studied strains exhibited a MDR phenotype, primarily conferred by the overexpression of efflux pumps (e.g., MexAB-OprM, MexCD-OprJ, MexXY, MexEF-OprN) and inactivation of the oprD. Genotypic characterization identified strains P113, P118, and T117 as ST11/O3 (ExoS+/ExoU−), whereas XM8 was ST385/O6 (ExoS+/ExoU−). Evolutionary analysis indicated the global dissemination of XM8-like clones, with a pronounced peak in 2023–2024. Crucially, the MDR of XM8 was further exacerbated by antibiotic resistance genes located on its non-transferable plasmid, pXM8-2. Enhanced surveillance and preemptive containment measures are urgently needed to mitigate the public health threat posed by these resistant lineages.