This paper deals with the genetic properties of R plasmids in Salmonella originated from pigs and cattle. The plasmid DNA was examined for incompatibility, stability and fertility inhibition(Fi), and gel electrophoresis was performed for isolation of plasmid DNA.
The results obtained were summerized as follows:
1. Among the 66 conjugative R plasmids from 44 pigs and 22 cattle, 61 R plasmids (92.4%) were Fi^- , whereas the remainder were Fi+.
2. The Inc groups of 66 R plasmids were determined with 7 standard plasmids. Twenty-six R plasmids were classified into Inc group Iα, H1, H2 or F1, 40 R plasmids being not classified with standard plasmids used, and the Inc group Iα (57.7%) was most frequent.
3. Inc groups Iα, H1, and F1 were identified in strains from swine, Inc groups H2 and F1 from cattle.
4. The plasmid DNA profiles in 16 Salmonella isolated from pigs and cattle were confirmed as being 1 to 10 fragments by the gel eletrophoresis. Their molecular weight ranged 1.0 to 90 megadalton.
5. The molecular weight of conjugative plasmids ranged 1.0 to 80 megadalton in 4 Salmonella (P-4, P-5, P-7 and P-8) isolated from pigs.
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