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

KT 359为屎肠球菌临床分离株，对卡那霉素、庆大霉素、红霉素和四环素耐药，携带多种质粒。质粒pKG（65.1kb）是从KT 359中分离得到的，编码卡那霉素和庆大霉素抗性。pKG的EcoR Ⅰ酶切图谱显示A ~ E五个片段，大小分别为50.2，11.5，2.0，0.7和0.7kb。pKG基因片段顺序为ACDEB顺时针方向。用于质粒接合转移的E.faecalis FA 2 -2和JH 2SS，或来自无质粒和药物敏感的屎肠球菌临床菌株KT 06的屎肠球菌KT 06 RF（利福平和梭孢酸抗性）和KT 06 SS（链霉素和壮观霉素抗性）菌株。pKG在粪肠球菌、屎肠球菌菌株中或在屎肠球菌和粪肠球菌菌株之间转移，在两小时交配后，分别以每个供体细胞约10 μ g<-4>、10 μ g<-5>或10 μ g<-4>的频率转移。将供体细胞暴露于无质粒的FA 2 -2或KT 06 RF菌株的培养物中，不会诱导交配实验中的质粒转移。在肉汤交配期间，目视未观察到交配聚集体。在显微镜观察下，在肉汤交配中观察到几个细胞的小交配聚集体，而在暴露于受体菌株FA 2 -2或KT 06 RF的培养滤液后，即使在显微镜下也没有观察到供体细胞的聚集体。这些结果表明，肠球菌接合质粒中存在着不同于粪肠球菌信息素诱导质粒转移系统的另一种有效转移系统。

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.