crisprcas系统与志贺菌耐药的关系word格式论文.docxVIP

摘要CRISPR2阴性志贺菌均携带oxa，而tetA的携带率较低；IS与oxa、sul2及cat 之间的差异有统计学意义，且相应耐药基因阳性菌株的CRISPR/Cas系统中多存在IS；CRISPR1、CRISPR2的spacer数目与oxa、tetA、sul2、cat之间的差异均有统计学意义，且相应耐药基因阳性的菌株中，CRISPR1、CRISPR2 的spacer多为较少的2 条、1 条。5.10 条spacer共匹配上25 个质粒。与spacer3匹配的质粒pUMNF18_IncFV 上发现耐药基因aph、aadA2、dfrA12、aprR、hph 和tem，spacer3 仅存在于4 株志贺菌，其均携带tem。6. 敏感株和接合转移多耐药志贺菌株中均检测到cas1、cas2及孤立的CRISPR3，接合转移后cas1、cas2及CRISPR3未发生改变。敏感株和诱导耐多药志贺菌株中均检测到CRISPR1、CRISPR2 及cas 基因簇，诱导耐药后，cse1-cas3 基因两端的4 个碱基发生变异。结论1. 59 株志贺菌的多耐药率和耐药基因携带率均较高。2.多耐药志贺菌中，CRISPR1、CRISPR2的间隔序列数目均较少，且其CRISPR/Cas系统中多存在插入序列。CRISPR1间隔序列数目较少的志贺菌携带耐药基因的个数较多。3.接合转移后，志贺菌中孤立的CRISPR3无变化。诱导耐药后，cse1-cas3基因两端的4 个碱基发生变异。关键词志贺菌耐药CRISPRcas 基因IIAbstractShigellaisthemainpathogenofinfectiousdiarrhea,causingbacillarydysentery, itstreatmentmainlydependsonantibiotics,however,variationtookplacefrequently withantibioticsabuse,andmanyresistanceShigellastrainsemerged.Horizontalgene transfer(HGT)isthemainwaythatbacteriaacquireresistancegenes.CRISPRexist widelyinbacteriaandarchaebacteria,composedofrepeatandspacer,togetherwith cas, limit HGT.ObjectiveWeanalyzedtherelationshipbetweenCRISPR/Cassystemandantibiotic resistancethroughdetectingtheCRISPR/Cas,antibioticresistanceandresistance genes.Moreover,weanalyzedchangesofCRISPR/Cassysteminmulti-drug resistanceShigellastrainsstructuredbydruginducedandconjugation,sothatwecan clarifythe regulationofCRISPR/Cas systemto drugresistanceinShigella.MethodsRecoveryandidentification59Shigellastrains,Kirby-Bauerwasusedtodetect thedrugresistance,PCRwasusedtodetectresistancegenesandcas;PCRamplified andsequencedCRISPR,CRISPRtargetandBLASTwereusedtoanalyzethe homologybetweenspacerandplasmids;ClustalX2.1andBioEditwereusedto analyzechanges ofCRISPR/Cassystem in multi-drugresistanceShigellastrains structured bydruginduced and conjugation.ResultsTheresistanceratesofthe59ShigellaisolatestoAM,CF,TE,C,SXTandNOR wererespectively,59.32%,27.12%,72.88%,50.85%,67.80%and16.95%.The multi-drugresistanceratewas 57.63%.The positive rates ofresistancegenes were r