title: Changes in pulsed-field gel electrophoresis patterns in clinical isolates of enterohemorrhagic Escherichia coli O157:H7 associated with loss of Shiga toxin genes.
abstract: Pulsed-field gel electrophoresis (PFGE) of XbaI-digested DNA fragments of enterohemorrhagic Escherichia coli (EHEC) O157:H7 strains showed disappearance of a 70- or 80-kb fragment in their patterns associated with loss of Shiga toxin genes during maintenance or subcultivation. Hybridization experiments with a DNA probe complementary to Shiga toxin sequences revealed that the Shiga toxin genes in the parental strain were located on fragments the same size as the lost fragments from the toxin-negative derivatives. The evidence indicates that PFGE pattern of EHEC O157:H7 may change due to loss of Shiga toxin genes, which is likely to be associated with curing of Shiga toxin gene carrying phages in vitro.
authors.affiliation: Department of Bacteriology and Pathology, Kanagawa Prefectural Public Health Laboratory, Nakao 1-1-1, Asahi-ku, Yokohama 241-0815, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Murase
authors.forename: S
authors.initials: S
authors.lastname: Yamai
authors.forename: H
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D001427:Bacterial Toxins / Q000032:analysis / Q000235:genetics*; D015139:Blotting, Southern; D004269:DNA, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D019453:Escherichia coli O157 / Q000235:genetics* / Q000254:growth & development; D017353:Gene Deletion; D005798:Genes, Bacterial; D006801:Humans; D022603:Shiga Toxins
chemical_list: D001427:Bacterial Toxins; D004269:DNA, Bacterial; D022603:Shiga Toxins