rmtB阳性猪大肠杆菌及其接合子中Ⅰ类整合子研究

Research on Class Ⅰ Integrons of rmtB Positive Isolated E.coli and Their Transconjugants from Pig Farms

为分析48株猪源16SrRNA甲基化酶基因rmtB阳性大肠杆菌及其接合子中Ⅰ类整合子的流行情况和分子特性,作者采用PCR和DNA序列测定方法对48株猪源rmtB阳性大肠杆菌及其接合子携带的Ⅰ类整合子进行分析,用微量稀释法测定rmtB阳性大肠杆菌及其接合子对20种抗菌药物的敏感性,并分析比较基因盒阳性菌和阴性菌的耐药率。结果:48株猪源rmtB阳性大肠杆菌中,5′-保守端的检出率为100%,3′-保守端检出率为77.1%,基因盒的检出率为58.3%;45株接合子中,5′-保守端的检出率为84.4%,3′-保守端检出率为62.2%,基因盒检出率为42.2%。与原菌株比较,接合子携带的耐药基因盒发生了丢失、获得以及置换等变化。比较基因盒阳性和阴性大肠杆菌对20种抗菌药物的耐药率,除对大观霉素、安普霉素差异显著外,对其他抗菌药物的耐药性无显著差异。研究结果表明,Ⅰ类整合子/基因盒系统在rmtB阳性大肠杆菌及其接合子中广泛存在,其5′-保守端、3′-保守端以及耐药基因盒的检出率存在差异,在质粒接合传递过程中,Ⅰ类整合子出现了基因盒的捕获或重组,基因盒携带率与rmtB阳性大肠杆菌及其接合子的多重耐药性无关。

The objective of this study was to analyze the prevalence and characteristics of class Ⅰ integrons in 48 isolated rmtB positive E.coli and their transconjugants.The Polymerase Chain Reaction and DNA sequencing were used to analyze the detection rate and the conformation characteristics of class Ⅰ integrons in 48 rmtB positive E.coli and their 45 transconjugants.The microdilution method were applied to analyze the resistance of 48 rmtB positive E.coli isolates and their transconjugants against 20 antibacterial agents.And statistical method was used to compare the resistant ratio between cassette-positive and cassette-negative isolated E.coli.Of all 48 rmtB positive E.coli,100%,77.1% and 58.3% strains were positive for 5＇-conserved segment,3＇-conserved segment and the gene cassettes,respectively.And 84.4%,62.2%,42.2% of 45 transconjugants were positive for 5＇-conserved segment,3＇-conserved segment and the gene cassettes,respectively.Missing,acquisition and replacement of gene cassettes were happened in the procedure of transconjugation.Indistinctive deviation of the resistant ratio between gene cassette-positive and gene cassette-negative isolated E.coli to 20 antibacterial agents were demonstrated except for spectinomycin and apramycin.The results indicated that class Ⅰ integrons were widely prevalent in rmtB positive E.coli and their transconjugants.And the detection rates for 5＇-conserved segment,3＇-conserved segment and gene cassettes were different.Gene capture and recombination were taken place in the procedure of transconjugantion.The ratios of gene cassette were unrelated to the multi-drug resistance of rmtB positive E.coli and their transconjugants.