中文摘要：

为研究16S rRNA甲基化酶rmtB在猪肠道菌中的传播方式,用脉冲场凝胶电泳（PFGE）分别对来源于A、B猪场的48株rmtB阳性大肠埃希氏菌进行基因分型;用膜接合试验研究rmtB基因的水平传播方式;用微量稀释法对rmtB阳性菌及其接合子进行药敏试验。有45株rmtB阳性大肠埃希氏菌（45/48）能进行PFGE分型,可分为28种不同的PFGE基因型。其中来源于A猪场的20株菌可分为12种基因型,来源于B猪场的25株菌可分为16种基因型;46株rmtB阳性菌可以通过接合试验将rmtB基因及其介导的耐药性传递给受体菌E.coliC600和E.coli488 Rifr,接合频率从4.6×10-13-3.0×10-6不等,接合子对卡那霉素、阿米卡星、妥布霉素、西梭米星、萘替米星、庆大霉素6种二脱氧链霉胺类抗生素均高度耐药（MIC≥512μg/mL）。结果表明,rmtB基因位于接合性质粒上,该基因在两猪场的大肠埃希氏菌中既存在克隆传播,又存在水平传播,以水平传播为主。

英文摘要：

To study the transfer mode of rmtB in Enterobacteria isolates from pig farms.Pulse field gel electrophoresis（PFGE） were carried out to study the genotyping of 48 rmtB-positive E.coli isolates from A and B pig farms.Conjugation experiments was carried out to study the horizontal transfer mode of rmtB genes by filter mating method.Broth microdilution method was applied to test susceptibility of rmtB-positive isolates and their transconjugants to antimicrobial agents.Among 48 rmtB-positive E.coli isolates,45 strains were successfully typed by PFGE.Total of 28 different PFGE profiles were obtained,and 12 different PFGE profiles were obtained in 20 isolats from A pig farm,16 different PFGE profiles were acquired in 25 isolats from B pig farm.All the rmtB genes located in 46 rmtB-positive isolates were easily transferred to recipients of E.coli C600 and E.coli 488 Rifr.Conjugative transfer frequencies varied from 4.6×10-13 to 3.0×10-6 cells per recipient cell.And all 46 transconjugants showed extraordinarily high-level resistance to 4,6-substituted deoxystreptamine（MICs512 μg/mL）.It concluded that the rmtB gene was located on a conjugative plasmid in E.coli.Both horizontal gene transfer and clonal expansion were responsible for the dissemination of rmtB gene and horizontal gene transfer was predominant in E.coli isolates from two pig farms.