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Title: Clonal structure and virulence factors in strains of Escherichia coli of the classic serogroup O55
Authors: Rodrigues, Josias
Scaletsky, Isabel Cristina Affonso [UNIFESP]
Campos, Leila Carvalho [UNIFESP]
Gomes, Tania Aparecida Tardelli [UNIFESP]
Whittam, Thomas S.
Trabulsi, Luiz Rachid [UNIFESP]
Universidade de São Paulo (USP)
Universidade Federal de São Paulo (UNIFESP)
Issue Date: 1-Jul-1996
Publisher: Amer Soc Microbiology
Citation: Infection And Immunity. Washington: Amer Soc Microbiology, v. 64, n. 7, p. 2680-2686, 1996.
Abstract: Virulence properties and genetic variation as determined by multilocus enzyme electrophoresis were studied in 70 strains of Escherichia coli O55, 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 O55:H6, O55:H7, and O55:H51 and nonmotile (O55: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 O55: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 O55: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.
ISSN: 0019-9567
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