Escherichia coli produtora de toxina Shiga ( STEC): marcadores de Virulência e análise clonal

• Ano de defesa: 2006
• Autor(a) principal: Vaz, Tânia Mara Ibelli [UNIFESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• dARK ID: ark:/48912/001300001tq93
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo (UNIFESP)
• Palavras-chave em Português: Escherichia coli produtora de toxina Shiga; STEC/EHEC; PFGE; Escherichia coli; Toxinas Shiga; Eletroforese em Gel de Campo Pulsado; Shiga toxin-producing Escherichia col; serotypes; phenotypical characteristics; virulence markers; Shiga Toxins; Electrophoresis, Gel, Pulsed-Field
• Link de acesso: http://repositorio.unifesp.br/handle/11600/9472

Forty eigth Shiga toxin-producing Escherichia coli (STEC) strains, the majority from human origin, and thirty non-STEC strains carrying eae and belonging to the same serogroups of STEC strains, and isolated between 1976 and 2003 were studied. Phenotypical traits, virulence characteristics and genetic diversity were evaluated. The majority of STEC strains was isolated in two distinct periods: some strains were recovered from a retrospective study (1976-99), and other strains from a prospective study (2000-03). STEC and non-STEC strains from human origin were from sporadic and unrelated cases of infection, except for two strains isolated from one patient. STEC strains belonging to serotypes O111:H8(H-), O26:H11 e O157:H7 prevailed. Differences on the prevalence of serotypes during the two periods were observed; while O111:H8(H-) e O26:H11 STEC strains prevailed during the period 1976-99, only one O111:H- STEC strain was identified during the period 2000-03. The inability to ferment rhamnose and dulcitol was mostly associated with O26 and O118 strains, whereas O111 STEC strains failed to decarboxylate lysine. The majority of the STEC strains was susceptible to all drugs; however, multi-resistant strains were detected mainly among O111:H- and O111:H8 STEC strains. All O157:H7 STEC strains carried stx2. Strains belonging to O93:H19 and O77:H18 harbored stx1 and stx2 sequences, and the remaining STEC strains carried only stx1. Except for O93:H19, O77:H18 e O55:H19 serotypes, all STEC strains carried eae. A close relationship was seen between intimin types, serotypes and diarrheagenic groups of E. coli. The presence of ehxA gene varied according to the serotypes. Multiple PFGE patterns were found among STEC strains of distinct serotypes. Moreover, PFGE restriction patterns of STEC strains differed substantially from those observed among non-STEC strains of the same serogroup except for O26 strains. Based on the indistinguishable PFGE pattern seen in two O157:H7 STEC strains, it can be suggested the first probable occurrence of an O157:H7 outbreak in Brazil. Human infections caused by STEC strains of distinct phenotypical and genotypical features occurred in our setting since the late 1970.