[Genetic map and structure in "Escherichia coli" K12 of a resistance plasmid isolated from "Salmonella ordonez" (author's transl)].

A resistance plasmid called R IP173 has been transferred into E. coli K12 from a multiresistant strain of S. ordonez isolated during an epidemic in Dakar. This plasmid mediates for colicine Ib production and resistance to ampicillin, streptomycin, spectinomycin, kanamycin, chloramphenicol, tetracycline and sulfonamides. It is transducible "en bloc" by the phage P1-kc between strains of E. coli K12. Compatibility studies have shown that R IP173 belongs to the fi- class, I1 group. It is transferred "en bloc" in conjugation experiments between E. coli K12 strains. But during transfers from S. ordonez into E. coli, incomplete variants are obtained, lacking different markers. A deletion map was obtained after analysis of 19 different variants, and it is suggested that the loss of markers results from the loss of genetic material during transfer. In this particular case, the deletions observed in transduction or conjugation experiments lead to identical genetic maps.