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A Protocol to Characterize the Morphological Changes of Clostridium difficile in Response to Antibiotic Treatment
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Haem is crucial for medium-dependent metronidazole resistance in clinical isolates of Clostridioides difficile

Ilse M Boekhoud1, Igor Sidorov1, Sam Nooij1,2

  • 1Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands.

The Journal of Antimicrobial Chemotherapy
|April 20, 2021
PubMed
Abstract

Insights

Heme is crucial for Clostridioides difficile resistance to metronidazole, independent of the pCD-METRO plasmid. This finding explains previously unexplained metronidazole resistance in C. difficile infections.

Area of Science:

  • Microbiology
  • Antimicrobial Resistance
  • Molecular Biology

Background:

  • Metronidazole was a primary treatment for Clostridioides difficile infection, but resistance is emerging.
  • Plasmid pCD-METRO contributes to metronidazole resistance, but does not account for all cases.

Purpose of the Study:

  • To investigate plasmid-independent metronidazole resistance mechanisms in C. difficile.
  • To identify factors contributing to metronidazole resistance in clinical isolates.

Main Methods:

  • Antimicrobial susceptibility testing on various agar media.
  • Whole Genome Sequencing (WGS) of selected C. difficile isolates.
  • Analysis of Minimum Inhibitory Concentrations (MIC) in the presence of heme.

Main Results:

  • Nearly all C. difficile isolates showed increased metronidazole MIC in a heme-dependent manner.
  • A specific single nucleotide polymorphism (SNP) in the hsmA gene was identified in a metronidazole-resistant lineage.
  • This resistant lineage (PCR ribotype 010/MLST ST15) included strains with and without the pCD-METRO plasmid.

Conclusions:

  • Heme plays a critical role in medium-dependent metronidazole resistance in C. difficile.
  • The hsmA gene SNP is associated with a distinct metronidazole-resistant lineage.
  • Understanding these mechanisms is vital for managing C. difficile infections effectively.

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