Characterization of the Escherichia coli O157:H7 Outbreak Strain Whose Shiga Toxin 2 Gene Is Inactivated by IS1203v Insertion

Abstract

SUMMARY: A total of 12 enterohemorrhagic Escherichia coli (EHEC) O157:H7 strains were isolated during a recent outbreak in a nursery school in Ehime Prefecture, Japan. These isolates were considered to be derived from a common strain when analyzed using an IS-printing method and pulsed-field gel electrophoresis. PCR analysis revealed that the isolates harbor stx 1 , stx 2 , eae, and hlyA. However, assessment of the production of the Stx proteins revealed that these isolates produced Stx1 but not Stx2. We determined their stx 2 variants such as stx 2c and found that the size of the PCR product was much larger than the expected size. Sequencing of the entire stx 2 gene revealed that a 1310-bp fragment was inserted into the coding region of the Stx2A subunit and that the sequences of the insert were identical to those of IS1203v. According to the sequences around the insertion site, additional amino acid residues should be attached at the C-terminus of the A subunit, which may hamper the Stx2 complex formation. Finally, this study also suggested that such an insertion may lead to the misinterpretation of results when screening EHEC isolates for virulence genes by PCR.

Evolution of a zoonotic pathogen: investigating prophage diversity in enterohaemorrhagic Escherichia coli O157 by long-read sequencing

“…A number of studies have demonstrated similar integration and excision into and out of stx genes (Asano et al , 2013; Park et al , 2013; Toro et al , 2015). Under certain conditions the loss of Stx prophages and Stx activity has been demonstrated, indicating that Stx activity may be a negative factor in certain cases and an advantage in others (Park et al , 2013).…”

Bile salts and ferric iron-induced PMRAB dependent resistance to camps in EHEC O157:H7

“…EHEC serotype O157:H7 is the most important pathogen in North America, the United Kingdom and Japan (Kaper et al, 2004). The pathogenic strain is so diverse in nature; twelve EHEC O157:H7 strains were isolated during a recent outbreak in a nursery school in Ehime Prefecture, Japan alone (Asano et al, 2013).…”

Inhibition of verotoxin (VT) 2 absorption into systemic blood from intestine by repeated administration of bovine immune colostral antibody against VT2 in mice

“…Conclusion: These results suggest that absorption of VT2 from the intestine was inhibited by repeated administration of bovine immune colostral antibody against VT2 at early Introduction Food poisoning caused by Escherichia coli O157:H7 continues to occur in Japan. 1,2 Treatment for this type of infection generally does not involve antibiotics, 3e5 as verotoxin 2 (VT2) released from E. coli O157:H7 killed by antibiotics induces serious complications, such as hemolytic uremic syndrome (HUS), thrombotic thrombocytopenic purpura, and brain damage. 6e8 The authors have reported the neutralizing efficacy of bovine immune colostral antibody against VT2 in mice and beagle dogs.…”