This Article Full Text (PDF) Other Versions of this Article: AEM.00316-07v1 73/20/6360    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cookson, A. L. Articles by Attwood, G. T. Search for Related Content PubMed PubMed Citation Articles by Cookson, A. L. Articles by Attwood, G. T. Agricola Articles by Cookson, A. L. Articles by Attwood, G. T.

 Previous Article  |  Next Article 

Appl. Environ. Microbiol. doi:10.1128/AEM.00316-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Molecular subtyping and genetic analysis of the enterohemolysin (ehxA) gene from Shiga toxin-producing Escherichia coli and atypical Enteropathogenic E. coli

Food, Metabolism & Microbiology Section, Food & Health Group, AgResearch, Grasslands Research Centre, Tennent Drive, Palmerston North, and Enteric Reference Laboratory, ESR Kenepuru Science Centre, Porirua, New Zealand

^* To whom correspondence should be addressed. Email: adrian.cookson{at}agresearch.co.nz.

	Abstract

Analysis of the distribution of virulence factors between different Escherichia coli pathotypes, including Shiga toxin-producing E. coli (STEC), may provide some insight into the mechanisms by which different E. coli cause disease and the evolution of distinct E. coli types. The aim of this study was to examine the DNA sequence of enterohemolysin, a plasmid-encoded toxin that readily causes the hemolysis of washed sheep erythrocytes and to assess the distribution of enterohemolysin subtypes in E. coli isolated from various human and animal sources. The 2997 bp ehxA gene was amplified from 227 of 356 (63.8%) stx- and/or eae-positive E. coli strains isolated from cattle and sheep and from 24 of 25 (96.0%) STEC isolated from human diarrheal disease. Using PCR and restriction fragment length polymorphism (RFLP) analysis of ehxA, six distinct PCR-RFLP types (A to F) were observed with subtypes A and C constituting 91.6% of all the ehxA-positive strains. Subtype A was mainly associated with ovine stx-only strains (P < 0.001) and subtype C was associated with bovine eae-positive strains (P < 0.001). Eleven ehxA alleles were fully sequenced phylogenetic analysis indicated the presence of three closely related (> 95.0%) ehxA sequence groups, one of which included eae-positive strains (subtypes B, C, E and F) and the other two including mainly eae-negative STEC strains (subtypes A and D). In addition to being widespread in STEC, stx-negative eae-positive strains (atypical enteropathogenic E. coli) isolated from cattle and sheep also have similar ehxA subtypes and hemolytic activity.