Genomic Evolution and Virulence Association of Clostridioides difficile Sequence Type 37 in China

Background: Clostridioides difficile sequence type (ST) 37 is one of the most prevalent genotypes circulating in China. However, its genomic evolution and virulence determinants were rarely explored. Results: Here we performed whole-genome sequencing on a collection of 48 ST37 isolates and included additional 277 ST37 genomes from public domain in a phylogenetic analysis. The 325 genomes were clustered into six major clades, with region-dependent distributions, harbouring an array of antibiotic -resistance genes. The ST37 strains from China were divided into four distinct subclades, showing five importation times and international sources. Isolates associated with severe infections exhibited significantly higher toxin productions, tcdB mRNA levels, and sporulation capacities ( P < 0.001). KEGG analysis showed 10 metabolic pathways were significantly enriched in the mutations among isolates associated with severe CDI ( P < 0.05). Gene mutations in glycometabolism, amino acid metabolism and biosynthesis virtually causing instability in protein activity were correlated positively to the transcription of tcdR and negatively to the expression of toxin repressor genes, ccpA and codY . Conclusions: C. difficile ST37 in China formed four distinct genetic subclades with five independent import routes. Gene mutations in certain important metabolic pathways are associated with severe symptoms and correlated with higher virulence in C. difficile ST37 isolates. Funding Statement: This work was supported in part by a Major Science and Technology Medicine and Healthcare in Zhejiang (WKJ-ZJ-2107) and by a Key Research and Development Program of Shandong (2019JZZY011018). Declaration of Interests: All authors declare that they have no competing interests. Ethics Approval Statement: This study was approved by the Ethics Committee of the Hangzhou Medical College.