Abstract
Six R-plasmids of Gram negative bacteria isolated from poultry in Karachi region designated as pFK-2, pFK-6, pFK-7, pFK-8a, pFK13 and pFK-20 were studied for various genetic properties such as fi′ character, phage restriction and phage propagation in order to characterize them. Regarding their fi character, two (pFK-2 and pFK-7) were found to fi′ and four (pFK-6, pFK-8a, pFK-13 and pFK20) were found to be fi+ . None of the R plasmids tested neither restrcited phages T6, Plkc, Mucts, ǾX174 and λ of E. coli and P22 of Salmonella nor propagated the phages MS2, M13, f2, If1 and IKe. Frequency of transmission between E. coli strains of these R plasmids was also calculated and was found to be quite high during HFT state.
