Clonal structure and virulence factors in strains of Escherichia coli of the classic serogroup O55

Infect Immun. 1996 Jul;64(7):2680-6. doi: 10.1128/iai.64.7.2680-2686.1996.

Abstract

Virulence properties and genetic variation as determined by multilocus enzyme electrophoresis were studied in 70 strains of Escherichia coli 055, a common serogroup of enteropathogenic E. coli (EPEC), a major cause of infantile diarrhea in developing countries. Nearly 40% of the strains were originally isolated in Brazil and represented serotypes 055:H6, 055:H7, and 055:H51 and nonmotile (055:H-) strains. The analysis of electrophoretic variants of 20 enzymes defined seven distinct electrophoretic types (ETs). ET 1 was represented by 41% of the strains, including strains which usually hybridized with DNA probes for the intimin gene (eaeA), the EPEC adherence plasmid (EAF), and the gene for the pilin subunit of the bundle-forming pilus (bfpA). The ET 1 strains were also typically serotype 055:H6, displayed localized adherence (LA) in tissue culture assays, and were positive in the fluorescent-actin staining test for intimate cell adherence. These same characteristics were observed in the closely related ETs 2 to 4, which clustered in the same branch as ET 1. No known virulence marker could be identified in ET 6. ET 5 included 23 strains, all of which carried the eaeA gene but otherwise displayed a striking array of distinct virulence traits. This ET was represented by 055:H7 strains with phenotypes as diverse as the simultaneous expression of LA and diffuse adherence and the ability to form a newly described adherence pattern, called LA-like adherence. The results suggest that ET 5 marks a special pathogenic clone with a propensity to acquire virulence factors which may facilitate the emergence of new pathogenic strains.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Brazil
  • Diarrhea / microbiology
  • Enzymes / genetics
  • Escherichia coli / classification*
  • Escherichia coli / genetics
  • Escherichia coli / pathogenicity*
  • Escherichia coli Infections / microbiology
  • Genes, Bacterial
  • Genetic Variation
  • Humans
  • Infant
  • Polymorphism, Genetic
  • Serotyping
  • Virulence / genetics

Substances

  • Enzymes