J Vet Sci.  2012 Jun;13(2):139-144. 10.4142/jvs.2012.13.2.139.

Molecular characterization of Escherichia coli O157:H7 strains isolated from different sources and geographic regions

  • 1Departamento de Ciencias Biologicas, Fundacao Oswaldo Cruz, CEP 21041-210, Rio de Janeiro, Brazil. regua@ensp.fiocruz.br
  • 2Departamento de Bromatologia e, Universidade Federal Fluminense, CEP 24220-008, Rio de Janeiro, Brazil.
  • 3Departamento de Microbiologia e Parasitologia, Universidade Federal Fluminense, CEP 24220-008, Rio de Janeiro, Brazil.
  • 4Departamento de Microbiologia e Imunologia, Universidade do Estado do Rio de Janeiro, CEP 20550-030, Rio de Janeiro, Brazil.


Escherichia (E.) coli serotype O157:H7 is a globally distributed human enteropathogen and is comprised of microorganisms with closely related genotypes. The main reservoir for this group is bovine bowels, and infection mainly occurs after ingestion of contaminated water and food. Virulence genetic markers of 28 O157:H7 strains were investigated and multilocus enzyme electrophoresis (MLEE) was used to evaluate the clonal structure. O157:H7 strains from several countries were isolated from food, human and bovine feces. According to MLEE, O157:H7 strains clustered into two main clonal groups designated A and B. Subcluster A1 included 82% of the O157:H7 strains exhibiting identical MLEE pattern. Most enterohemorrhagic E. coli (EHEC) O157:H7 strains from Brazil and Argentina were in the same MLEE subgroup. Bovine and food strains carried virulence genes associated with EHEC pathogenicity in humans.


enterohemorrhagic Escherichia coli; molecular characterization; O157:H7; virulence

MeSH Terms

Cattle Diseases/epidemiology/*microbiology
Enterohemorrhagic Escherichia coli/genetics/*isolation & purification/pathogenicity
Escherichia coli O157/*genetics/*isolation & purification/pathogenicity
Food Microbiology
Gene Expression Regulation, Bacterial/physiology
Genetic Markers
Polymerase Chain Reaction/veterinary
Shiga Toxin 1/genetics/metabolism
Shiga Toxin 2/genetics/metabolism


  • Fig. 1 Isoenzymatic relationships among the Escherichia coli O157 strains.


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