Navegando por Palavras-chave "Escherichia coli produtora de toxina Shiga"

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    Escherichia coli produtora de toxina Shiga ( STEC): marcadores de Virulência e análise clonal
    (Universidade Federal de São Paulo (UNIFESP), 2006-12-31) Vaz, Tânia Mara Ibelli [UNIFESP]; Guth, Beatriz Ernestina Cabilio [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    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.
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    Estudos sobre o potencial de virulência e filogenia de amostras de Escherichia coli do sorotipo O113:H21
    (Universidade Federal de São Paulo (UNIFESP), 2011-02-22) Santos, Luis Fernando dos [UNIFESP]; Guth, Beatriz Ernestina Cabilio [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    In this study 37 O113:H21 Escherichia coli strains isolated from human infections (03 samples), the animal reservoir (33 samples) and food (1 sample) in different regions of Brazil, were analyzed for their genotypic and phenotypic virulence traits and genetic and phylogenetic backgrounds. The presence of the stx gene, defining the STEC pathotype was observed in all samples of non-human origin. Human samples, lacking this gene, were classified as non-STEC. The search for genes related to the production of toxins, adhesins and autotransporter proteins revealed the occurrence of distinct virulence profiles among samples of different origins. Among the STEC strains the profile composed of ehxA, subAB, epeA, espP, lpfO113, iha and saa, associated or not to cdt-V was the most prevalent. Non-STEC isolates harbored only astA, lpfO113 and iha. The genotype stx2dactivatablewas found in most of the STEC samples. High mass plasmids occurred in 25 of the 37 studied strains, but only in STEC group these plasmids could be confirmed as being the STEC O113 megaplasmid pO113. STEC isolates were also investigated for the occurrence of subtypes of genes and ehxA and regarding the enterohemolysin gene only the subtype A was found; in relation to saa, four distinct subtypes of this gene were present among the studied strains. These subtypes corresponded to variants of 500 to 800 base pairs. Cytotoxicity assays revealed the ability for the expression of subAB and cdt-V genes in 13 and 07 STEC strains respectively. Interaction assays using Caco-2 and T84 cell lines demonstrated that 13 strains had the capacity of invading the cells. Ability to form biofilm in different temperatures was observed in the majority of the studied strains. The search for the presence and expression of curli and type I fimbriae related genes were found to give positive results for the majority of the strains; however this fact had no correlation with biofilm production. Transcription of adhesin genes saa, iha and lpfO113 were investigated by RT-PCR, being the majority of the strains positive in such assays. Once more, there was no correlation between the RT-PCR results and the phenotypic virulence properties investigated. Distinct clusters were identified by PFGE analysis among the studied strains. Genetic similarity indices ranged from 65 to 100% among these clusters. MLST demonstrated the existence of phylogenetic relationship among O113:H21 STEC strains of different origins. These results indicate the presence in our settings of O113:H21 STEC isolates carrying virulence properties commonly found only in O113:H21 clones associated with SHU cases in other countries.