SNP genotyping of enterohemorrhagic Escherichia coli O157:H7 isolates from China and genomic identity of the 1999 Xuzhou outbreak

- 64 SNPs were used to type 325 Chinese O157:H7 isolates into 5 SNP genotypes (SGs).
- SG-1 was further divided into 2 subtypes with SG-1.1 subtype associated with the 1999 Xuzhou outbreak.
- The most potent stx2 subtype, stx2a, is only carried by SG-1 which caused the Xuzhou outbreak.
- Parallel spread of a limited number of SGs in China.

Enterohemorrhagic Escherichia coli O157:H7 is a well-known pathogen as a cause of diarrhea, hemorrhagic colitis (HC), and hemolytic uremic syndrome (HUS). Single nucleotide polymorphisms (SNPs) have been widely used to determine genetic relatedness and epidemiological relationship of O157:H7. Little is known of genetic diversity of Chinese O157:H7 isolates and their relationships with global isolates.The minimum sets of 32 SNPs each from Manning et al. and Clawson et al. were used to type 325 Chinese O157:H7 isolates. The 64 SNPs divided the Chinese O157:H7 isolates into 5 SNP genotypes (SG-1-SG-5). The most common SGs were SG-5 (79.69%) and SG-1 (14.46%). Human isolates concentrated in SG-1 and SG-5, and there is only 1 human isolates in SG-3. The 47 isolates in SG-1 were further divided by an additional SNP sourced from Xuzhou21 genome into 2 subtypes (SG-1.1 and SG-1.2). Strains in SG-1.1 caused the 1999 Xuzhou deadly outbreak. Our Chinese isolates have been found to belong to a limited number of SNP genotypes and are represented by distantly related clades in Manning et al. and lineages in Claswon et al., suggesting parallel spread of these SNP genotypes in China.