革兰氏阴性杆菌院内感染菌株的质粒分析

ANALYSIS OF PLASMIDS IN NOSOCOMIAL STRAINS OF GRAM-NEGATIVE BACILLI

对1987年至1989年我院所分离的115株革兰氏阴性杆菌院内感染菌株进行了质粒分析。结果表明除肺炎杆菌、沙雷氏菌和变形杆菌各1株未分离出质粒外。其余菌株均分离出质粒。共分离出质粒367个,平均每株细菌3.19个。367个质粒分属36种不同分子量,介于1.0kb～132kb之间。 5.5kb、3.6kb、2.0kb在我院细菌中出现最为频繁,均各占总菌株的22％以上。这些质粒在绿脓杆菌、大肠杆菌、肺炎杆菌、沙雷氏杆菌和变形杆菌中均有存在,在我院的院内感染中呈流行趋势。 通过质粒消除试验和药敏分析,5.5kb质粒可能与β—内酰胺抗生素的耐药有关;3.6kb质粒可能是编码对链霉素、卡那霉素和庆大霉素联合耐药的基因。2.0kb质粒可能决定氯霉素的耐药。35kb和11kb分别与5.5kb和3.6kb质粒在耐药方面的作用相同。

One hundred and fifteen strains of nosocomial Gram-negative bacilli isolated from 1987 to 1989 were studied. All of these strains demonstrated the presence of plasmids except three isolates. Three hundred and sixty-seven plasmids were demonstrated from these strains, with the average of 3.19 plasmids per strain. The molecular weigh of these plasmids were between 1.0 kb and 132 kb. Totally there were 36 kinds of plasmids with different molecular weight. 5.5 kb, 3.6 kb and 2.0 kb plasmids were more prevalent in our hospital than others.More than 22% of strians possessed these plasmids.They could be found in all the species bacilli which were investigated, including Pseudomonas aerugitiosa, Esch-erichia colit Klebsiella Pneumoniat Serratia spp. and Proteus spp. and seemd to be epidemic in hospital enviroment. The plasmids were analysised by combining plasmid elimination test with drug susceptibility test. 5.5 kb plasmid seemed to be related to resistance to β-lactam antibiotics. Resistance to streptomycin, kanaycin and gentamicm seemed to be mediated by 3.6 kb plasmid and 2.0 kb plasmid may be the plasmid DNA that coded resistance to chloramphenicol. The functions of 35 kb and 11 kb plasmids seemed to be similar to those of 5.5 kb and 3.6 kb plasmids respectively.