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Molecular Characterization of, and Antimicrobial Resistance in, Clostridioides difficile from Thailand, 2017-2018

Korakrit Imwattana1,2, Papanin Putsathit3, Daniel R Knight1,4

  • 1School of Biomedical Sciences, The University of Western Australia, Nedlands, Australia.

Microbial Drug Resistance (Larchmont, N.Y.)
|May 6, 2021
PubMed

Insights

Antimicrobial resistance is a key factor in Clostridioides difficile infection (CDI) spread. This study found common resistance to clindamycin, erythromycin, moxifloxacin, and rifaximin in Thai C. difficile strains, particularly RT 017.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Genomics

Background:

  • Antimicrobial resistance (AMR) significantly contributes to the pathogenesis and global spread of Clostridioides difficile infection (CDI).
  • Inadequately regulated antimicrobial use in regions like Thailand creates a concerning environment for the emergence and dissemination of resistant pathogens.
  • Fluoroquinolones have been previously linked to outbreaks of CDI, highlighting the need for understanding resistance patterns.

Purpose of the Study:

  • To characterize antimicrobial resistance (AMR) profiles of clinical Clostridioides difficile strains isolated in Thailand.
  • To investigate the genotypic basis of observed antimicrobial resistance through whole-genome sequencing and AMR genotyping.
  • To correlate specific genetic markers with phenotypic resistance in C. difficile isolates.

Main Methods:

  • Isolation and culture of C. difficile from stool samples, followed by toxin profiling and PCR ribotyping.
  • Antimicrobial susceptibility testing using the agar incorporation method.
  • Whole-genome sequencing and AMR genotyping on a subset of characterized C. difficile strains.

Main Results:

  • 321 C. difficile strains were analyzed, with RT 017 being the most prevalent (18%), followed by RT 014 (12%) and RT 020 (7%).
  • High rates of resistance were observed for clindamycin, erythromycin, moxifloxacin, and rifaximin, particularly in RT 017 strains.
  • AMR genotyping confirmed strong genotype-phenotype correlations for moxifloxacin and rifaximin resistance. erm-class genes were linked to high-level clindamycin/erythromycin resistance. A specific PBP3 substitution (Y721S) was associated with increased meropenem MIC, though not sufficient for resistance.

Conclusions:

  • Clostridioides difficile strains in Thailand exhibit significant resistance to commonly used antimicrobials like clindamycin, erythromycin, moxifloxacin, and rifaximin.
  • Genetic determinants, including erm-class genes and specific PBP3 mutations, play a role in the observed resistance phenotypes.
  • No resistance was detected against metronidazole, vancomycin, or fidaxomicin, suggesting these remain effective treatment options.
Keywords:
Clostridioides difficileThailandantimicrobial resistanceepidemiologygenotype

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