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<p>Increasingly, <i>tcdA</i>/<i>tcdB</i> qPCR is being used to diagnose <i>Clostridioides difficile</i> infections (CDI). Under the hypothesis that toxin genes’ quantification through Ct values could potentially improve clinical accuracy, this study aimed to assess the linearity of the <i>C. difficile</i> assay on the QIAstat-Dx<sup>®</sup> Gastrointestinal Panel 2 (GI2 Panel) and to correlate bacterial to toxins load. Four analytical and thirty-five clinical toxigenic <i>C. difficile</i> isolates were quantified using three validated standard curve qPCR assays targeting <i>adK</i>, <i>tcdA</i> and <i>tcdB</i> genes. Of these, twelve were then tested to characterize the linearity of the <i>C. difficile</i> assay on the QIAstat-Dx<sup>®</sup> GI2 Panel. Statistical analysis of the Ct values of <i>adK</i>, <i>tcdA</i> and <i>tcdB</i> obtained from standard curves presented an excellent linear fit (slopes range of 1.008–1.010 ± 0.001). A dynamic range of 1,000–1,000,000 copies/mL with R<sup>2</sup> ≥ 0.97 was established for the QIAstat-Dx<sup>®</sup> GI2 Panel’s <i>C. difficile</i> assay. The correlation among <i>tcdA</i>/<i>tcdB</i> and <i>adK</i> genes allows extrapolation to pathogen concentration. The QIAstat-Dx<sup>®</sup> GI2 Panel’s <i>C. difficile</i> assay demonstrated a wide linear range, allowing the accurate quantification of gene-encoding toxins A and B. This, in turn, presents a tool that could be key in establishing the relevance of toxin concentration and, potentially, a Ct cutoff at the time of CDI.</p>

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Use of PCR cycle threshold values for toxins A and B quantification in Clostridioides difficile infections

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年5月28日

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  • Rebecca Smith-Aguasca,
  • Nestor Camenforte,
  • Lara Rodríguez,
  • Sergio Herrera,
  • Katariina Vara,
  • Dietrich Lueerssen,
  • Frederick van Deursen,
  • Carla Camprubí-Font,
  • Luis Peñarrubia,
  • Oriol Vidal

摘要

Increasingly, tcdA/tcdB qPCR is being used to diagnose Clostridioides difficile infections (CDI). Under the hypothesis that toxin genes’ quantification through Ct values could potentially improve clinical accuracy, this study aimed to assess the linearity of the C. difficile assay on the QIAstat-Dx® Gastrointestinal Panel 2 (GI2 Panel) and to correlate bacterial to toxins load. Four analytical and thirty-five clinical toxigenic C. difficile isolates were quantified using three validated standard curve qPCR assays targeting adK, tcdA and tcdB genes. Of these, twelve were then tested to characterize the linearity of the C. difficile assay on the QIAstat-Dx® GI2 Panel. Statistical analysis of the Ct values of adK, tcdA and tcdB obtained from standard curves presented an excellent linear fit (slopes range of 1.008–1.010 ± 0.001). A dynamic range of 1,000–1,000,000 copies/mL with R2 ≥ 0.97 was established for the QIAstat-Dx® GI2 Panel’s C. difficile assay. The correlation among tcdA/tcdB and adK genes allows extrapolation to pathogen concentration. The QIAstat-Dx® GI2 Panel’s C. difficile assay demonstrated a wide linear range, allowing the accurate quantification of gene-encoding toxins A and B. This, in turn, presents a tool that could be key in establishing the relevance of toxin concentration and, potentially, a Ct cutoff at the time of CDI.