[Genetic and molecular characteristics of the conjugative R-plasmids of S. typhimurium].

The molecular genetic properties of R plasmids from 8 strains of S. typhimurium isolated in hospitals of the Far East of the USSR were studied. It was shown that conjugative R plasmids of S. typhimurium were characterized by belonging to the Inc F1 group, rigorous control of replication, the fi+ type and the transfer frequency of 10(-3) to 10(-4) per a donor cell. The plasmid profile of the S. typhimurium strains was represented by 2 plasmids: conjugative with a molecular weight of about 64 MD and nonconjugative with a molecular weight of 2 MD. The conjugative R plasmids of the hospital strain VG 103 of S. typhimurium were characterized by molecular genetic identity. They were derivatives of the pVG 103 plasmid.