Abstract
Pulsed-field gel electrophoresis (PFGE) has been used as a reliable epidemiological tool to identify the possible source and route of infection by Shiga-toxin producing Escherichia coli (STEC) O157. However, it has been found that some strains could not be subjected to the analysis because their DNAs are easily degraded. To produce strain-specific profiles of such strains, we used a method of amplifying DNA sequences flanking infrequent restriction sites (infrequent-restriction-site PCR; IRS-PCR) . Fifty-two strains of E. coli O157 were typed into 12 and 14 types by IRS-PCR patterns from DNAs digested with XbaI and HhaI and those with BlnI and HhaI, respectively. These data suggest that selection of an appropriate set of restriction enzymes will provides more discrimination patterns. In 18 of the 52 strains, that gave individual PFGE patterns, 11 IRS-PCR patterns were shown. Remaining 34 strains that were untypeable by PFGE were classified into 3 IRS-PCR types, indicating that some of those strains were possibly related.
