Análise genética do gene da enterotoxina east1 em amostras de escherichia coli enteropatogênica (epec)

• Ano de defesa: 2014
• Autor(a) principal: Silva, Lucas Emanuel Pinheiro da [UNIFESP]
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• dARK ID: ark:/48912/001300002jv9j
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo (UNIFESP)
• Palavras-chave em Português: enteroaggregative e; coli; escherichia coli enteroagregativa; e; coli diarreiogênica
• Link de acesso: https://sucupira.capes.gov.br/sucupira/public/consultas/coleta/trabalhoConclusao/viewTrabalhoConclusao.jsf?popup=true&id_trabalho=950760; http://repositorio.unifesp.br/handle/11600/46743

The enteroaggregative E. coli heat-stable enterotoxin 1 (EAST1) encoded by astA gene has been found in enteropathogenic E. coli (EPEC) strains. However, it is not sufficient to simply probe strains with an astA gene probe because many astA genes contain a deletion that eliminates the first 8 codons of the protein product. In one study, 100% of O26, O111, O145, and O157 strains examined possessed a mutant astA lacking the first 8 codons, including the initiation codon. In this study, 222 EPEC (70 typical and 152 atypical) isolates were tested for the presence of the astA gene sequence by PCR and sequencing. The astA gene was amplified from 54 strains, 11 typical and 43 atypical. Sequence analysis of the PCR products showed that 25 strains, 7 typical and 18 atypical, had an intact astA gene. A subgroup of 7 atypical strains had a variant type of the astA gene sequence, with four non-synonymous nucleotide substitutions. The remaining 22 strains had mutated astA gene with nucleotide deletions or substitutions in the first 8 codons. The RT-PCR results showed that the astA gene was transcribed only by the strains carrying either the intact or the variant type of the astA gene sequence. Southern blot analysis indicated that astA is located in EAF plasmid in typical strains, and in plasmids of similar size in atypical strains. Strains carrying intact astA genes were more frequently found in diarrheic children (14,3%) than in non-diarrheic children (1,8%) (P = 0.011). In conclusion, our data suggest that the presence of an intact astA gene may represent an additional virulence determinant in both EPEC groups.