New Insights Into the Molecular Characteristics of Binary Toxin-Producing Clostridioides difficile Strains in China: A Comparative Genomics Study

Abstract

Abstract Binary toxin (CDT)-producing Clostridioides difficile is associated with severe clinical symptoms and high mortality rates. However, the fundamental genomic factors that underpin the differentiated prevalence of CDT-producing C. difficile strains in China remain to be elucidated. To provide a comprehensive view of the genetic characteristics, this study comprehensively analyzed whole-genome sequences of CDT-producing C. difficile strains from China. The number of unique accessory genes in sequence type (ST)-5 strains, which are predominant in China, increased steadily with the increasing number of genomes sampled, while the accumulation curve for ST-1 strains was shallower. This suggests that ST-5 may have an open pangenome, whereas ST-1 may have a relatively conservative and stable pangenome. The pathogenicity locus (PaLoc) variants of Clades 1, 2 and 5 were found to share a common genetic organization, with the CDT locus (CdtLoc) showing lower variability than PaLoc. PaLoc in Clade 3 exhibits an insertion of transposon Tn6218, which is clade-specific. The flexibility of the C. difficile accessory genome has facilitated the development of divergent lineages characterized by the presence of evolutionarily advantageous genetic traits. This genetic diversification has led to enhanced antimicrobial resistance, increased virulence and improved metabolic capacities, which collectively augment the ability of C. difficile to survive and proliferate.