大肠杆菌超突变子产生的分子基础及其在耐药性发生和转移中的作用

发布时间：2018-01-13 05:34

本文关键词：大肠杆菌超突变子产生的分子基础及其在耐药性发生和转移中的作用　出处：《吉林大学》2007年博士论文　论文类型：学位论文

【摘要】： 超突变子的突变频率是正常菌株突变频率的1000倍以上，超突变子的出现，可能使细菌更适应目前治疗量的抗菌药物浓度，加速耐药性的产生。本研究首先测定了318株不同来源大肠杆菌对环丙沙星等12种抗菌药物的MIC、MPC，抑菌作用最强的是兽医临床上使用较少的AM，耐药率仅为0.94％，AMO、TET耐药率最高，达到90％以上：其中以耐6种抗菌药物的菌株数最多，达到88株；ENR的MPC_(90)与MPC_(90)／MIC_(90)均最小，AM、CIP、OFL次之，说明这几种药物在临床选择耐药突变菌株的能力较小，GEN、NOR、SPE等药物的MPC_(90)／MIC_(90)较大，有较强的选择突变能力。测定24株菌株的突变频率，筛选出3株超突变子，PFGE分型表明，，其带型与其他菌株差异显著。采用长片段PCR、Western-blotting、质粒互补实验对大肠杆菌野生型和超突变子的MMR重要组分MutS进行研究，超突变子mutS基因存在大片段缺失，MutS无表达，无活性，说明大肠杆菌超突变子发生的分子基础是其MMR系统重要组分MutS存在缺陷。耐药基因检测和膜蛋白分析表明，其耐药表型和基因型相符。进行滤膜接合试验表明，以超突变子为受体菌的转接合子的转化频率较高，接合在超突变子中容易发生，超突变子促进了耐药基因在不同菌株之间的转移。
[Abstract]:The mutation frequency of super mutator is normal strain mutation frequency of more than 1000 times, super mutants, may make the bacteria more adapt to the current treatment volume concentration of antibiotics, accelerate resistance. In this study, the determination of 318 different strains of Escherichia coli to ciprofloxacin 12 antibacterial agents such as MIC, MPC, antibacterial the strongest effect is to use fewer veterinary clinical AM, drug resistance rate is only 0.94%, AMO TET, the highest resistant rate reached more than 90%: one to 6 kinds of antimicrobial resistant strains was the most, to reach 88 strains; ENR MPC_ (90) and MPC_ (90) / MIC_ (90) was the smallest. AM, CIP, OFL, showed this kind of drug resistant mutant strains in the clinical ability of small, GEN, NOR, SPE and other drug MPC_ (90) / MIC_ (90), there is a strong selection of mutations ability. The mutation frequency was determined in 24 strains, 3 strains were screened with super mutants. PFGE type table Ming, the belt type and other strains were significantly different. The PCR long fragment, Western-blotting, plasmid complementation of Escherichia coli mutants and wild type super important constituent of MMR MutS were studied. The super mutant mutS gene deletions in MutS, no expression, no activity, said the molecular basis of Escherichia coli from super bright which place is an important group of the MMR MutS system defects. Detection of drug resistance genes and membrane protein analysis showed that the phenotype and genotype of resistance. Conjugation test shows that the membrane, with ultra high frequency of transformation for the mutator conjugations of receptor strain, joint easily occurred in the super mutants, super mutants to promote the transfer of resistance genes between different strains.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2007
【分类号】：S852.61;R378.2

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