Genomic and phenotypic characterization of a Clostridioides difficile strain of the epidemic ST37 type from China

<i>Clostridioides difficile</i> strains of sequence type (ST) 37, primarily including PCR ribotype (RT) 017, are prevalent in mainland China. Our study aimed to compare the major virulence factors of an epidemic <i>C. difficile</i> isolate of ST37 type (Xy06) from China with the well-characterized <i>C. difficile</i> reference strains R20291 (RT027) and CD630E (ST54), as well as a Chinese ST54 strain (Xy07) isolated from the same hospital. The Xy06 genome was predicted to harbor two complete prophages and several transposon-like elements. Comparative analysis of PaLoc revealed a truncated tcdA gene, a functional tcdB gene, a functional tcdC gene, and well-conserved tcdR and tcdE genes. Phenotypic comparisons showed that Xy06 was a robust producer of TcdB, readily sporulated and germinated, and strongly bound to human gut epithelial cells. In a mouse model of <i>C. difficile</i> infection, Xy06 was more virulent than strains CD630E and Xy07 and was comparable to strain R20291 in virulence. Our data suggest the potential threat of the epidemic ST37 strains in China.