Identification of Shiga toxin-producing Escherichia coli possessing insertionally inactivated Shiga toxin gene

We have investigated the Shiga toxin genes of Shiga toxin-producing Escheri chia coli (STEC) strains, using polymerase chain reaction (PCR) amplifying the full lengths of these genes. As a result, we found the Shiga toxin 2 ge ne which was insertionally inactivated by an insertion sequence (IS). This IS element mas identical to IS1203V which has been also found in inactivate d Shiga toxin 2 genes, and was inverted at the same site as in the previous paper On the other hand, both Shiga toxin 2 genes were different (98.3% id entity). These suggested that IS1203v independently inserted into each Shig a toxin 2 genes, and STEC strains possessing the insertionally inactivated Shiga toxin genes are most likely to have a wide distribution. Amplificatio n of the full length of the Shiga toxin gene is one of the effective method s to detect the gene no matter where the IS element is included, i.e., the insertion can be reflected in the size of amplicon.