Caracterização eletretroforetica e expressão das fimbrias Fy e 31A de amostrasde Escherichia coli de origem bovina

AUTOR(ES)
DATA DE PUBLICAÇÃO

1990

RESUMO

Escherichia coli strains associated with diarrhea and septicemic infections of cattle were studied to determine the genetic expression of FY and 31A fimbriae. The strains 31A+: BZ43, BZ2468 and 31A, and FY+: Att25, 54-5, 2147-4 and 11a, were evaluated for enterotoxin production (STI and LT), VT, hemolysin, antibiotic resistance, mannose resistant RBC hemagglutination, and reaction with specific antisera. The characterization of fimbriae involved electron microscopy, SDS-PAGE of total, surface and membrane proteins and Western blotting. Conjugative plasmids in the strains were transferred and analyzed for FY and 31A expression. Hemagglutination, SDS-PAGE of total and surface proteins and reaction with specific antisera allowed the location of the fimbrial subunits at 20 kDa for FY and 17 kDa for 31A. Strain 11a, originally grouped as FY by others, was classified as 31A based on SDS-PAGE of surface proteins and reaction with specific antisera. Strains Att25, BZ2468 and 31A had conjugative plasmids coding antibiotic resistance marks, but transconjugants failed to express the fimbriae, suggesting it could be located in the bacterial chromosome. Strain BZ43 (31A) was mutagenized using TnphoA transposon and mutants with negative hemagglutination of bovine RBC were assayed with specific antiserum, and tested for adhesion to HeLa cells in tissue culture and pathogenicity in the mouse competition assay. Loss of hemagglutinating capacity was related to the lack of the 31A fimbriae subunit (17 kDa) on SDS-PAGE of surface proteins. One mutant strain showed fimbriae under electron microscopy. The absence of fimbriae in the other mutant strain was related to a missing 35 kDa membrane protein. Both mutants reacted positively with absorbed anti-31A antiserum suggesting that fímbrial epithopes were expressed. Loss of bovine RBC hemagglutination did not altered the adhesion patter to HeLa cells (AD), either in the fimbriated or in the non-fimbriated mutant strain. Strain BZ43 and the fimbriated mutant strain were non-pathogenic to 3 day old mice in the competition assay. The lack of hemagglutination seemed not to interfere with adhesion properties of the mutant strain in this assay

ASSUNTO(S)

escherichia coli

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