[Research methods of R factors (author's transl)]

After having outlined the routine methods for the study of drug resistance plasmids used at highly specialized centres such as the London Enteric Reference Laboratory, the AA. examine the most practical methods of a pure and simple way of discovering R factors in enterobacteria. A brief reference is made to some of the in vivo transfer techniques before reducing the various possibilities of in vitro survey to essentials. The experimental conditions realized by some AA. for mating in liquid media which represent the most commonly used method for the study of R factors in enterobacteria are pointed out as an example. Finally, a brief reference is made to other technique such as the mating possibilities on membrane filter in solid media and "facilitated mating" in the cellophane device according to Chabbert.