Snp Genotyping Of Shiga Toxin-producing Escherichia Coli O157:H7Isolates Of China

Shiga toxin-producing Escherichia coli O157:H7is a well-known zoonotic 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, explore the population and evolution and epidemiological relationship of O157:H7. There are few reports of genetic diversity of Chinese O157:H7isolates and their relationships with global isolates.The minimum sets of32SNPs each from Manning et al. and Clawson et al. were used to type325Chinese O157:H7isolates. The total64SNPs divided the Chinese O157:H7isolates into5SNP genotypes (SG-1to SG-5). The most common SGs were SG-5(79.69%) and SG-1(14.46%). Human isolates concentrated in SG-1and SG-5, and there is only1human isolates in SG-3. The47isolates in SG-1were further divided into2subtypes (SG-1.1and SG-1.2) by an additional SNP sourced from Xuzhou21genome. Strains in SG-1.1caused the1999Xuzhou deadly outbreak.Of325Chinese isotates,136isolates were typed by MLST into4types:ST23, ST24, ST96and ST97. MLST results are consistent with SNP typing with the latter offering slightly higher resolution. ST24is divided into SG-2and SG-3while ST23is divided into SG-4and SG-5. However ST96and ST97belonged to the same SG (SG-1). All SG-1.1isolates are ST96while all SG-1.2isolates belong to ST97.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.Thirty-six isolates representing different SGs were included for sequencing and comparative analysis. All the isolates has a total of2486SNPs, including809synonymous mutations and1195non-synonymous mutations,475inter-gene SNPs,7stop mutations.Phylogenetic tree based on SNP concatenation could separate all SG-5strains suggesting the high resolution of SNPs of Chinese O157:H7isolates to capture the genetic diversity of Chinese O157:H7isolates, In addition,3ST24isolates of SG-2and SG-3were divided into the three branches, revealing substantial genomic differences. The outbreak related strains in SG-1.lcan be separated from SG-1using these SNPs.