Genetic studies of virulence factors of avian Escherichia coli strains

Abstract

Ten pathogenic E. coli strains were examined for plasmid types and pathogenicity. Some strains were found to produce colicin and to have drug resistance determinants on a single conjugative plasrnid while others harbored apart Col V and H plasmids. These plasmids were derepressed with a transfer frequency of around 10-6 and 10-1 and did not induce serum resistance or virulence in the recipient ceils of E. coli K₁₂ and of normal flora E. coli strains of chickens, it was the verified that, in the strains studied, the serum resistance and the determinants for virulence are coled by cromossomal genes or have their expression dependant on chromossomal genes.