BGI completed the sequencing of the E. coli samples within three days, using the relatively new Ion Torrent platform (owned by Life Technologies). This third-generation sequencing platform has the advantage of speed of sequencing and relatively long read lengths, which is useful for sequencing and identifying novel bacterial strains.
Bioinformatics analysis showed that the strain at the center of the latest outbreak is highly infectious and toxic. According to the results of the draft assembly (available at ftp://ftp.genomics.org.cn/pub/Ecoli_TY-2482), the estimated genome size of this new E. coli strain is about 5.2 megabases (Mb). The bacterium is an EHEC (enterohemorrhagic) serotype O104 E. coli strain, but a new serotype that has not been previously associated with any E. coli outbreaks.
Comparative sequence analysis showed that this bacterium has 93% similarity with the EAEC (enteroaggregative) 55989 E. coli strain, previously isolated in the central Africa and linked to cases of serious diarrhea. The new European strain of E. coli also features DNA sequences related to those involved in the pathogenicity of hemorrhagic colitis and hemolytic-uremic syndrome, potentially acquired through horizontal gene transfer. The genome also carries a number of antibiotic resistance genes, including resistance to aminoglycoside, macrolides and beta-lactam antibiotics.
BGI and its collaborators are studying the bacterial virulence genes, expression profiles, drug resistance, and gene transfer mechanisms. It also hopes to develop diagnostic kits. The sequences of this new E. coli strain have been uploaded to NCBI (SRA No: SRA037315.1).
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