Genetic and molecular characterization of R plasmids incompatible with R387 (IncK)

More than 70 conjugative R plasmids have been isolated from wild-type strains originating mainly in South-East Europe and identified as incompatible with the reference plasmid R387 of the incompatibility group K. These plasmids, governing different resistance patterns, have been characterized as P1 cotransducible species of between 50 and 60 mega-daltons. In contrast to the genetic similarity between all these plasmids and the reference type R387, their DNA revealed different digestion patterns after EcoRI treatment, although a number of common fragments could be identified. The molecular and genetic properties of these plasmid species demonstrate a phylogenetic relatedness.