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KMID : 0893420080090010075
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Journal of Veterinary Science
2008 Volume.9 No. 1 p.75 ~ p.83
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The expression of plasmid mediated afimbrial adhesin genes in an avian septicemic Escherichia coli strain
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Eliana Guedes Stehling
Tatiana Amabile Campos
Marcelo Brocchi
Vasco Ariston de Carvalho Azevedo
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Abstract
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An Escherichia coli strain (SEPT13) isolated from the liver of a hen presenting clinical signs of septicaemia had a LD50 of 4.0 × 105 CFU/ml in one-day-old chickens, expressed Ia, Ib, E1, E3, K and B colicins and aerobactin. The strain was ampicillin and streptomycin resistant, and found to have fimA, csgA and tsh DNA related sequences; it could adhere to and invade HEp-2 and tracheal epithelial cells, expressed fimbriae (observed by electron microscopy), and had five plasmids of 2.7, 4.7, 43, 56, and 88 MDa. Transposon mutagenesis of strain SEPT13, with transposon TnphoA, resulted in a mutant strain named ST16 that had a LD50 of 1.2 × 1012 CFU/ml. All other biological characteristics of strain ST16 were the same as those detected for strain SEPT13 except for the migration of an 88 MDa plasmid to the 93 MDa position indicating the insertion of the transposon into the 88 MDa plasmid. The 93 MDa plasmid of strain ST16 was transferred, by electroporation assay, to non-pathogenic receptor strains (E. coli strains K12 MS101 and HB101), resulting in transformant strains A and B, respectively. These strains exhibited adhesion properties to in vitro cultivated HEp-2 cells but did not have the capacity for invasion. The adherence occurred despite the absence of fimbriae; this finding suggests that the 88 MDa plasmid has afimbrial adhesin genes.
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KEYWORD
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adhesion, avian, Escherichia coll, plasmids
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