Comparative Whole Genome Sequence Analysis and Biological Features of Clostridioides difficile Sequence Type 2^‡

Area of Science:

• Microbiology
• Genomics
• Infectious Diseases

Background:

• Clostridioides difficile sequence type 2 (ST2) is a significant genotype in China.
• Genomic characteristics and biological phenotypes of Chinese ST2 strains require detailed investigation.

Purpose of the Study:

• To elucidate the genomic features and biological phenotypes of 182 Clostridioides difficile ST2 strains isolated in China between 2011 and 2017.
• To compare the genetic diversity, antibiotic resistance, toxin production, and sporulation capacity of different ST2 lineages.

Main Methods:

• Whole-genome sequencing and core genome phylogenetic analysis.
• PCR ribotyping (RT), antibiotic resistance profiling, toxin concentration measurement, and sporulation capacity assays.

Main Results:

• ST2 strains segregated into two main lineages (L1 and L2), with L2 further dividing into SL2a and SL2b, predominantly found in China.
• Chinese SL2b strains (RT014 and RT020) showed no significant difference in antibiotic resistance.
• SL2b strains possessed a unique non-synonymous substitution in tcdB (Y1975D) and exhibited significantly lower Toxin B concentrations compared to L1 and SL2a.

Conclusions:

• Chinese Clostridioides difficile ST2 strains, particularly those in the SL2b sub-lineage, are characterized by a specific tcdB mutation and reduced Toxin B production.
• These findings suggest that the genomic and phenotypic traits of Chinese ST2 strains may be associated with milder C. difficile infections.