Escherichia coli Col V plasmids and their role in pathogenicity

Out of 1474 Escherichia coli strains belonging to 70 serogroups and 247 serologically not identified ones, colicin V producers were found in serogroups O78, O1, O7, O18 and also among the not identified strains. The molecular weight of Col V1 plasmid from the standard strain was 70 Mdal. The Col V plasmids carried by E. coli O78 strains isolated from a hospital outbreak in Hungary had a molecular weight of 78 Mdal and also 78 Mdal was the molecular weight of the Col V plasmid carried by Rivier's strain (designated 23), which had caused meningitis in Switzerland. The molecular weight of Col V plasmids of O1: K1, O21, O161 and serologically not identified E. coli strains isolated from sporadic cases was of 94 to 119 Mdal. In the case of three strains the increase of LD50 values, which means the decrease of virulence, resulted in the loss of colicin V production and the loss of Col V plasmid. It was demonstrated by introduction of a transposon, inactivating colicin V production, into a wild type E. coli strain that the production of colicin was not essential for the increase of virulence controlled by Col V plasmid. In the case of one strain the loss of both R and Col V plasmid resulted in a decrease of virulence. No plasmid other than R and Col V was carried by this strain. The virulence determining gene could be eliminated together with both plasmids, which means that this gene could be attached equally to Col V and R plasmid.