鲍曼不动杆菌错配修复基因mutL的序列及其系统进化关系分析

Molecular phylogenetic relationships of A. baumannii based on sequences of mismatch repair gene mutL

目的探讨中南大学湘雅二医院于2008-2009年临床分离到的不同基因型和耐药型的鲍曼不动杆菌的错配修复基因mutL的系统进化关系。方法以PCR扩增这一时期内5株分离自不同科室,具有不同基因型和耐药表型的鲍曼不动杆菌的错配修复基因mutL,运用软件ClustalX 1.83对mutL序列进行分析,基于该分析运用软件Mega 5.0采用邻接法(N-J法)构建系统进化树分析其系统进化关系。结果 (1)耐药型相同(对临床常用15种抗生素均耐药)的3株菌mutL序列完全一致,遗传距离为0.000;耐药型相似(对临床常用15种抗生素大多数敏感)的2株菌mutL序列相似度为98.95%,遗传距离为0.011,而与前3株的相对遗传距离大约分别为0.013和0.015;(2)序列分析显示这5株菌的mutL序列共发生了16个基因突变,其中有7个简约信息位点和9个自裔位点,这些突变导致了翻译过程中的12个错义突变、3个无义突变和2个同义突变。结论 (1)湘雅二医院2008-2009年发生过多重耐药鲍曼不动杆菌的院内交叉感染;(2)mutL序列中若干位点的基因突变会导致鲍曼不动杆菌耐药性变化,即错配修复基因mutL与鲍曼不动杆菌的耐药性状有关。

Objective To investigate the molecular phylogenetic relationships of A.baumannii with different genetypes and drug-resistant types isolated from August 2008 to 2009in Second Xiangya Hospital of Central South University.Methods Polymerase chain reaction（PCR）was conducted to amplify the mismatch repair gene mutL of 5 A.baumannii isolates with different genetypes and drug-resistant types from different medical departments.The sequences of mutL were analysed by ClustalX 1.83 and their evolutionary relations were built by using Mega 5.0based on Neighbor-Joining.Results The sequences of mutL of 3isolates with the same drug-resistant types（resistant to all the 15 commonly used antibiotics）were identical and the genetic distance was 0.000;the sequence similarity based on mutL of the other 2isolates（sensitive to most of the 15 commonly used antibiotics）was 98.95% and the genetic distance was 0.011,while their relative distances with the former 3isolates were about 0.013 and 0.015 respectively.By comparing the sequences of the 3resistant isolates with the other 2sensitive isolates,we found the same mutation in 7bases which result in 3missense mutations,2nonsense mutations and 2synonymous mutations.Conclusion The finding highly suggests that the hospital cross-infection of multiple drug-resistant A.baumannii existed from 2008 to 2009.Several genetic mutations in the sequence of mutL can result in drug resistance changes,in other words,the mismatch repair gene mutL relates with the drug resistance of A.baumannii.