Navegando por Palavras-chave "Escherichia coli Proteins/genetics"

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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.