title: Characterization of the Escherichia coli O157:H7 outbreak strain whose Shiga toxin 2 gene is inactivated by IS1203v insertion.
abstract: 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 stx1, stx2, eae, and hlyA. However, assessment of the production of the Stx proteins revealed that these isolates produced Stx1 but not Stx2. We determined their stx2 variants such as stx2c and found that the size of the PCR product was much larger than the expected size. Sequencing of the entire stx2 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.
authors.affiliation: Ehime Prefectural Institute of Public Health and Environmental Science, Ehime, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Asano
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Karasudani
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tanaka
authors.forename: Junko
authors.initials: J
authors.lastname: Matsumoto
authors.forename: Masako
authors.initials: M
authors.lastname: Okada
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Nakamura
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Kondo
authors.forename: Hiroto
authors.initials: H
authors.lastname: Shinomiya
mesh_terms: D002675:Child, Preschool; D004251:DNA Transposable Elements; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D005260:Female; D055786:Gene Knockout Techniques; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D058889:Molecular Typing; D016254:Mutagenesis, Insertional; D017422:Sequence Analysis, DNA; D022641:Shiga Toxin 2 / Q000235:genetics* / Q000378:metabolism
chemical_list: D004251:DNA Transposable Elements; D022641:Shiga Toxin 2