Isogenic strain of Escherichia coli 0157 : H7 that has lost both Shiga toxin 1 and 2 genes

Citation
P. Feng et al., Isogenic strain of Escherichia coli 0157 : H7 that has lost both Shiga toxin 1 and 2 genes, CL DIAG LAB, 8(4), 2001, pp. 711-717
Citations number
22
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Immunology
Journal title
CLINICAL AND DIAGNOSTIC LABORATORY IMMUNOLOGY
ISSN journal
1071-412X → ACNP
Volume
8
Issue
4
Year of publication
2001
Pages
711 - 717
Database
ISI
SICI code
1071-412X(200107)8:4<711:ISOEC0>2.0.ZU;2-D
Abstract
An Escherichia coli O157:H7 strain isolated from a patient with hemorrhagic colitis was found to exhibit two slightly different colony morphology type s on differential medium, Each morphological type, designated TT12A and TT1 2B, was isolated, and serological testing using various assays confirmed th at both strains carried the O157 and the H7 antigens, Biochemical testing s howed that the strains had identical profiles on AP120E analysis and, like typical O157:H7 strains, did not ferment sorbitol or exhibit P-glucuronidas e activity. Analysis with a multiplex PCR assay showed that TT12B did not c arry the gene for either Shiga toxin 1 (Stx1) or Stx2, whereas these genes were present in TT12A and the toxins were produced. Apart from that, both s trains carried the +93 gusA mutation, the duster I ehxA gene for enterohemo lysin, and the eae gene for gamma -intimin, which are all characteristics o f the O157:H7 serotype. Phenotypic assays confirmed that both strains exhib ited enterohemolysin activity and the attachment and effacing lesion on HeL a cells. Multilocus enzyme electrophoresis analysis showed that the strains are closely related genetically and belong in the same clonal group. Pulse d-field gel electrophoresis (PFGE) typing of XbaI-digested genomic DNA reve aled that the two strains differed by two bands but shared 90% similarity a nd clustered in the same clade, All other non-Stx-producing O157:H7 strains examined clustered in a major clade that was distinct from that of Stx-pro ducing O157:H7 strains. The findings that TT12B was identical to TT12A, exc ept for Stx production, and its PFGE profile is also more closely related t o that of Stx-producing O157:H7 strains suggest that TT12B was derived from TT12A by the loss of both stx genes.