The molecular relatedness of R factors in enterobacteria of human and animal origin

The molecular length and DNA homology of R factors isolated from enterobacteria of human and animal origin have been examined. DNA from plasmids of the same compatibility group, whether of human or animal origin is indistinguishable, after allowance has been made for the regions coding for different antibiotic resistances. These results indicate that there is a common pool of R factors in man and ainmals.