Estudo dos fatores de virulencia de amostras de Escherichia coli patogenicas de origem aviaria (APEC) / Study of the virulence factors from avian pathogenic Escherichia coli strains (APEC)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Two pathogenic Escherichia coZi strains isolated from avian (APEC) showing c1inical signs of septicemia (817 and 821), and one isolated from avian showing c1inical signs of 8wollen Head 8yndrome (8H8 1 O), were selected from a total of 49 strains belonging to the Laboratory of Bacterial Molecular Biology, after a biological characterization regarding the presence of adhesion and invasion capacities to HEp-2 and HeLa cells, resistance profile to different antimicrobial drugs, presence of genes (detected by PCR) associated with pathogenicity, and plasmidial DNA profile. REP-PCR assay also was performed for separation of these strains in c10nal groups. Plasmids from these strains were transferred by conjugation assays to the non-pathogenic E. coZi strain HB 1 O 1. The analysis of the obtained recombinants strains, demonstrated that only recombinant strains derived from 817, one of these designated as 817-1, showed adhesion and invasion to these cells, indicating that the genes responsible for these characteristics are located in the transferred plasmid (70 MDa). 8ince the adhesion and invasion capacities of 821 and 8H8 1 O strains were not detected in recombinant strains where the transference of plasmids presents in these two strains occurred, indicates that the genes responsible for these characteristics are not plasmid-mediated. The location of these genes could be chromosomal, or thus plasmidial, but with chromosomal control. The mutation of 817-1 strain, with TnphoA transposon, resulted in the lost of adhesion and/or invasion capacities to HEp-2 and HeLa cells, which indicate that the transposon insertion process had occur at genes associated with the described processo The tsh gene (temperature-sensitive hemagglutinin) from 821 strain, and aerobactin genes from 8H810 ifepC) and 821 (iucA) strains, also were not found in the recombinants strains. These results suggest that these genes could be located in chromosomal regions as well as the adhesion and invasion genes from these strains. This observation could indicate that the presence of possible "pathogenicity islands" in these strains, but other studies must be realized for confirmation of this hypothesis. The production of colicins (Ia, Ib, El, E3, B and K) by strain 8H810 also was transferred to the recipient strain, which indicate that this characteristic is expressed by genes located at the transferred plasmid (120 MDa). Using invasion assays to HEp-2 cells, 8canning Electron Microscopy and FA8 assay, it was possible to observe that the cellular invasion capacity from 817 strain is different of those processes described by others invasive E. coZi, Salmonella spp. and Shigella spp

ASSUNTO(S)

escherichia coli pathogenicity fatores de virulencia adesão adhesion avian ave patogenicidade virulence factors

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