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Cytolethal distending toxin gene cluster in enterohemorrhagic Escherichia coli O157:H- and O157:H7: characterization and evolutionary considerations.

ABSTRACT: We identified a cytolethal distending toxin (cdt) gene cluster in 87, 6, and 0% of sorbitol-fermenting (SF) enterohemorrhagic Escherichia coli (EHEC) O157:H(-), EHEC O157:H7, and E. coli O55:H7/H(-) strains, respectively. The toxin was expressed by the wild-type EHEC O157 strains and by a cdt-containing cosmid from a library of SF EHEC O157:H(-) strain 493/89. The cdt flanks in strain 493/89 were homologous to bacteriophages P2 and lambda. Our data demonstrate that cdt, encoding a potential virulence factor, is present in the EHEC O157 complex and suggest that cdt may have been acquired by phage transduction.

SUBMITTER: Janka A

PROVIDER: S-EPMC155755 | biostudies-literature | 2003 Jun

REPOSITORIES: biostudies-literature

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Cytolethal distending toxin gene cluster in enterohemorrhagic Escherichia coli O157:H- and O157:H7: characterization and evolutionary considerations.

Janka Andreas A Bielaszewska Martina M Dobrindt Ulrich U Greune Lilo L Schmidt M Alexander MA Karch Helge H

Infection and immunity 20030601 6

We identified a cytolethal distending toxin (cdt) gene cluster in 87, 6, and 0% of sorbitol-fermenting (SF) enterohemorrhagic Escherichia coli (EHEC) O157:H(-), EHEC O157:H7, and E. coli O55:H7/H(-) strains, respectively. The toxin was expressed by the wild-type EHEC O157 strains and by a cdt-containing cosmid from a library of SF EHEC O157:H(-) strain 493/89. The cdt flanks in strain 493/89 were homologous to bacteriophages P2 and lambda. Our data demonstrate that cdt, encoding a potential viru ...[more]

PMID: 12761152

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Project description:BackgroundAlthough serotype O157:H7 is the predominant enterohemorrhagic Escherichia coli (EHEC), outbreaks of non-O157 EHEC that cause severe foodborne illness, including hemolytic uremic syndrome have increased worldwide. In fact, non-O157 serotypes are now estimated to cause over half of all the Shiga toxin-producing Escherichia coli (STEC) cases, and outbreaks of non-O157 EHEC infections are frequently associated with serotypes O26, O45, O103, O111, O121, and O145. Currently, there are no complete genomes for O145 in public databases.ResultsWe determined the complete genome sequences of two O145 strains (EcO145), one linked to a US lettuce-associated outbreak (RM13514) and one to a Belgium ice-cream-associated outbreak (RM13516). Both strains contain one chromosome and two large plasmids, with genome sizes of 5,737,294 bp for RM13514 and 5,559,008 bp for RM13516. Comparative analysis of the two EcO145 genomes revealed a large core (5,173 genes) and a considerable amount of strain-specific genes. Additionally, the two EcO145 genomes display distinct chromosomal architecture, virulence gene profile, phylogenetic origin of Stx2a prophage, and methylation profile (methylome). Comparative analysis of EcO145 genomes to other completely sequenced STEC and other E. coli and Shigella genomes revealed that, unlike any other known non-O157 EHEC strain, EcO145 ascended from a common lineage with EcO157/EcO55. This evolutionary relationship was further supported by the pangenome analysis of the 10 EHEC str ains. Of the 4,192 EHEC core genes, EcO145 shares more genes with EcO157 than with the any other non-O157 EHEC strains.ConclusionsOur data provide evidence that EcO145 and EcO157 evolved from a common lineage, but ultimately each serotype evolves via a lineage-independent nature to EHEC by acquisition of the core set of EHEC virulence factors, including the genes encoding Shiga toxin and the large virulence plasmid. The large variation between the two EcO145 genomes suggests a distinctive evolutionary path between the two outbreak strains. The distinct methylome between the two EcO145 strains is likely due to the presence of a BsuBI/PstI methyltransferase gene cassette in the Stx2a prophage of the strain RM13514, suggesting a role of horizontal gene transfer-mediated epigenetic alteration in the evolution of individual EHEC strains.

Dataset Information

Cytolethal distending toxin gene cluster in enterohemorrhagic Escherichia coli O157:H- and O157:H7: characterization and evolutionary considerations.

Publications

Cytolethal distending toxin gene cluster in enterohemorrhagic Escherichia coli O157:H- and O157:H7: characterization and evolutionary considerations.

Similar Datasets

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