Patterns of insertion sequence (IS)
629,
norV genotype, and Shiga toxin (Stx) genotype distribution were investigated amongst 203 enterohemorrhagic
Escherichia coli O157 isolates collected in Yamaguchi Prefecture, Japan, between 2004 and 2013. A total of 114 IS
629 patterns were identified; these were divided into eight IS groups (A–H). Ninety isolates carried an intact
norV gene, whereas 113 isolates carried a
norV with a 204-bp deletion. Other than one isolate from IS group G, all isolates with an intact
norV belonged to groups A–F, whereas isolates with a mutant
norV belonged to IS groups G and H. Seven
stx genotypes were identified, and of those,
stx1a/
stx2a was predominant (n=105), followed by
stx2c (n=32) and
stx2a (n=27). The
stx1a/
stx2a genotype was associated with the mutant
norV isolates, whereas isolates with an intact
norV had the
stx2c genotype. Therefore, certain combinations of IS type and
stx genotype appear to be more frequent among O157 clades which may be useful for detection of predominant subtypes in the interest of public health.
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