TRANSPOSON MUTAGENESIS AND MEMBRANE-PROTEIN STUDIES IN AN AVIAN COLISEPTICAEMIC ESCHERICHIA-COLI STRAIN

The pathogenicity, antibiotic resistance, plasmid DNA and membrane pro tein profiles of a colisepticaemic Escherichia coli strain (362) isola ted from chickens was studied. It was verified that this strain harbou red at least five plasmids. One 88.0 MD plasmid is non conjugative and is responsible for the production of colicin V and serum resistance. The 43.0 MD plasmid is responsible for resistance to bactericidal acti vity of serum and ampicilin. Curing of these plasmids did not decrease the pathogenicity of the strain. Transposon mutagenesis (Tnpho A) of strain 362 yielded a non-pathogenic derivative strain which had lost a 40.7 kD membrane protein, which is not correlated to the aerobactin a nd enterochelin systems. We suggest that this protein subunit is invol ved in the pathogenicity process of avian septicaemic E. coli strains.