[Antibiotic resistance plasmids in Salmonella strains isolated from various sources]

Resistance of 60 Salmonella strains to aminoglycoside antibiotics was studied. It was found that 51 strains had a multiple resistance to the antibiotics used. By the antibiotic resistance phenotypes, the strains were divided into three major groups. Analysis of the extrachromosomal DNA revealed the presence of plasmids in 48 antibiotic resistant strains and 6 antibiotic sensitive strains. The plasmids transferred by conjugation to the E. coli recipient from 21 antibiotic resistant strains. The 150-kb plasmids transferred in all the strains. The 100-kb plasmids additionally transferred in 5 strains. The high molecular weight plasmids that transferred to the recipient strain by conjugation encoded resistance to all the aminoglycosides used.