Genotypic and phenotypic changes in the emergence of Escherichia coli O157:H7

J Infect Dis. 1998 Jun;177(6):1750-3. doi: 10.1086/517438.


Escherichia coli O157:H7 is a foodborne pathogen distinguished from typical E. coli by the production of Shiga toxins (Stx) and the inability to ferment sorbitol (SOR) and to express beta-glucuronidase (GUD) activity. An allele-specific probe for the GUD gene (uidA) and multilocus enzyme electrophoresis were used to elucidate stages in the evolutionary emergence of E. coli O157: H7. A point mutation at +92 in uidA was found only in O157:H7 and its nonmotile relatives, including a SOR+ O157:H clone implicated in outbreaks of hemolytic-uremic syndrome in Germany. The results support a model in which O157:H7 evolved sequentially from an O55:H7 ancestor, first by acquiring the Stx2 gene and then by diverging into two branches; one became GUD- SOR- , resulting in the O157:H7 clone that spread worldwide, and the other lost motility, leading to the O157:H clone that is an increasing public health problem in Europe.

MeSH terms

  • Escherichia coli Infections / microbiology*
  • Escherichia coli O157* / classification
  • Escherichia coli O157* / enzymology
  • Escherichia coli O157* / genetics
  • Genotype
  • Glucuronidase / genetics
  • Humans
  • Phenotype


  • Glucuronidase