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Background <p><i>Capnocytophaga canimorsus</i> (<i>C. canimorsus</i>) is a zoonotic pathogen transmitted by dogs and cats that can cause severe infections in humans. Antimicrobial susceptibility data remain limited, but increasing genomic evidence suggests that functional β-lactamase genes may be more widespread than previously recognized.</p> Methods <p>Three <i>C. canimorsus</i> isolates harboring class D β-lactamase genes were selected by genomic screening from a larger collection of the Global <i>Capnocytophaga</i> Consortium for detailed characterization: two isolates from human clinical infections from Sweden and New Zealand, and a commensal canine isolate from the Czech Republic. We used hybrid Illumina-Nanopore genome assemblies, phylogenetic analysis, and structural modeling to characterize the genomic context and the predicted protein features of the β-lactamase genes. The functional impact of the β-lactamases on antibiotic activity was assessed by minimum inhibitory concentration (MIC) testing and confirmed through recombinant expression in the β-lactamase-negative reference strain <i>C. canimorsus</i> 5 (Cc5).</p> Results <p>We detected <i>bla</i><sub>OXA-347</sub> in a canine isolate and, for the first time, in a clinical <i>C. canimorsus</i> isolate from human infection. Additionally, we identified a previously uncharacterized allele, newly designated <i>bla</i><sub>OXA-1422</sub>, in another clinical isolate. Both β-lactamases were chromosomally encoded without clear mobile genetic elements and were part of a distinct phylogenetic cluster within the OXA family. Structural modeling showed conserved class D β-lactamase architecture. Strains carrying either gene had elevated MICs for multiple β-lactams, and expression of each gene in Cc5 recapitulated these effects.</p> Conclusions <p>The identification and phenotypic characterization of OXA-type β-lactamases in clinical <i>C. canimorsus</i> isolates refine our understanding of β-lactamase diversity in this species and underscore the need for systematic investigations of β‑lactamase prevalence in this zoonotic pathogen.</p>

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β-lactamase genes in clinical isolates of Capnocytophaga canimorsus and description of a novel class D β-lactamase, OXA-1422

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月5日

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  • Zoja Germuskova,
  • Eleonora Pronzini,
  • Fanny Wegner,
  • Tim Roloff,
  • Tianyan Song,
  • Miroslava Barancekova,
  • Alois Cizek,
  • Michael Addidle,
  • Murray Robinson,
  • Marc Dieu,
  • Chaitanya Tellapragada,
  • Christian G. Giske,
  • Kirstine Kobberøe Søgaard,
  • Els M. Broens,
  • Francesco Renzi,
  • Adrian Egli

摘要

Background

Capnocytophaga canimorsus (C. canimorsus) is a zoonotic pathogen transmitted by dogs and cats that can cause severe infections in humans. Antimicrobial susceptibility data remain limited, but increasing genomic evidence suggests that functional β-lactamase genes may be more widespread than previously recognized.

Methods

Three C. canimorsus isolates harboring class D β-lactamase genes were selected by genomic screening from a larger collection of the Global Capnocytophaga Consortium for detailed characterization: two isolates from human clinical infections from Sweden and New Zealand, and a commensal canine isolate from the Czech Republic. We used hybrid Illumina-Nanopore genome assemblies, phylogenetic analysis, and structural modeling to characterize the genomic context and the predicted protein features of the β-lactamase genes. The functional impact of the β-lactamases on antibiotic activity was assessed by minimum inhibitory concentration (MIC) testing and confirmed through recombinant expression in the β-lactamase-negative reference strain C. canimorsus 5 (Cc5).

Results

We detected blaOXA-347 in a canine isolate and, for the first time, in a clinical C. canimorsus isolate from human infection. Additionally, we identified a previously uncharacterized allele, newly designated blaOXA-1422, in another clinical isolate. Both β-lactamases were chromosomally encoded without clear mobile genetic elements and were part of a distinct phylogenetic cluster within the OXA family. Structural modeling showed conserved class D β-lactamase architecture. Strains carrying either gene had elevated MICs for multiple β-lactams, and expression of each gene in Cc5 recapitulated these effects.

Conclusions

The identification and phenotypic characterization of OXA-type β-lactamases in clinical C. canimorsus isolates refine our understanding of β-lactamase diversity in this species and underscore the need for systematic investigations of β‑lactamase prevalence in this zoonotic pathogen.