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Detection of genetic and functional diversity of heat labile toxins produced by enterotoxigenic Escherichia coli (ETEC) isolated from humans in São Paulo

M Ang B E C Guth; Luís Carlos de Souza Ferreira; Congresso Instituto Ciências Biomédicas, IV (2002 São Paulo)

Resumos São Paulo: Comissão de Cultura e Extensão Universitária do ICB/USP, 2002

São Paulo Comissão de Cultura e Extensão Universitária do ICB/USP 2002

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  • Título:
    Detection of genetic and functional diversity of heat labile toxins produced by enterotoxigenic Escherichia coli (ETEC) isolated from humans in São Paulo
  • Autor: M Ang
  • B E C Guth; Luís Carlos de Souza Ferreira; Congresso Instituto Ciências Biomédicas, IV (2002 São Paulo)
  • Assuntos: MICROBIOLOGIA
  • É parte de: Resumos São Paulo: Comissão de Cultura e Extensão Universitária do ICB/USP, 2002
  • Descrição: Enterotoxigenic Escherichia coli (ETEC) strains represent one of the most important etiological agents of diarrhea in developing countries and characteristically produce at least one of two enterotoxins: heat-labile toxin (LT) and heat stable toxin (ST). LT, an AB type toxin, is composed of one toxic portion (A subunit), processed into A1 and A2 fragments, and five receptor binding subunits (B subunits), organized in a plasmid-located operon formed by two cistrons, extA and extB. In this work we evaluated the genetic diversity of LT-encoding genes among a group of 20 ETEC strains, including 10 LT/ST strains and 10 LT strains, isolated from diarrheic or non-diarrheic patients in São Paulo city. Restriction fragment length polymorphism (RFLP) of PCR-amplified fragments containing ext operon revealed 5 RFLP profiles following cleavage with Hph I, Hha I, Hinc II and Msp I. Moreover, sequencing of the complete ext operon of 9 polymorphic strains disclosed the presence of several point mutations leading to amino acid changes in 11 and 4 different positions at the A and B subunits, respectively. Affinity to the specific ganglioside receptor (GM1) was reduced in one LT variant carrying three different amino acid substitutions at the B subunit. Six LT variants with single amino acid changes at the A subunit were submitted to cytotoxic tests and at least one of them showed reduced activity on Vero cells with regard to the wild type toxin. The present results reveals extensive
    genetic diversity of the LT-encoding genes found among ETEC strains isolated in natural settings and may contribute to a better understanding of evolutionary patterns of the pathogen
  • Editor: São Paulo Comissão de Cultura e Extensão Universitária do ICB/USP
  • Data de criação/publicação: 2002
  • Formato: 1. (várias paginações) poster 195.; Disponível em CD-ROM.
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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