Pheromone Independent Efficient Transfer System in Conjugative Plasmid of Enterococcus that the Plasmid pKG (65.1kb) was isolated from Enterococcus faecium Clinical Strain

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KT359 was Enterococcus faecium clinical isolate, resistant to kanamycin, gentamicin, erythromycin and tetracycline, and harbors several plasmids. Plasmid pKG (65.1kb) was isolated from KT359 and encoded kanamycin and gentamicin resistance. EcoRI restriction profile of pKG exhibited five fragments A through E,and the molecular size was 50.2,11.5,2.0,0.7, and 0.7kb, respectively. The order of the fragments was clockwise order of ACDEB.The pKG transferred at high frequency in Enterococcus in broth mating. Recipient strains used in conjugative transfer of the plasmid were E.faecalis FA2-2 and JH2SS,or E.faecium KT06RF (rifampin and fuscidic acid resistance) and KT06SS (streptomycin and spectinomycin resistance) strains derived from plasmid free and drug sensitive E.faecium clinical strain of KT06. pKG transferred in E.faecalis, E.faecium strains, or between E.faecium and E.faecalis strains at a frequency of about 10^<-4>,10^<-5>, or 10^<-4> per donor cell after two hours mating, respectively. Plasmid transfers in mating experiments were not induced by exposure of the donor cell to culture filtrates of plasmid free FA2-2 or KT06RF strain. Mating aggregates were not observed visually during broth mating. Small mating aggregates of several cells were observed in the broth mating under microscopic observation, while aggregates of donor cells after being exposed to a culture filtrate of recipient strain, FA2-2 or KT06RF,were not observed even under microscope. These results indicate that there is another efficent transfer system in conjugative plasmids of Enterococcus, which is different from pheromone induced transfer system of E.faecalis plasmids.