主动外排系统acrAB在临床分离肺炎克雷伯菌中的分布和表达

目的：研究临床分离多重耐药肺炎克雷伯菌的耐药机制。检测肺炎克雷伯菌中有无类似大肠埃希菌主动外排系统acrAB的结构基因acrAB的分布和表达。方法：用聚合酶链反应(PCR)检测acrAB基因在临床分离的肺炎克雷伯菌和肺炎克雷伯菌标准菌株(ATCC 10031)中分布。用逆转录(RT)-PCR测定其mRNA表达水平。并对PCR扩增的ATCC 10031的acrAB基因片段进行序列分析。同大肠埃希菌acrAB基因的相应序列进行同源性比较。结果：在所有被检的临床分离肺炎克雷伯菌和ATCC 10031的染色体中均发现有类似大肠埃希菌的acrAB基因；肺炎克雷伯菌多重耐药菌株acrAB的mRNA水平显高于敏感野生株和耐药谱不同的菌株，而耐药谱不同的菌株仅略高于敏感菌株；PCR扩增的ATCC 10031的acrAB基因片段同大肠埃希菌acrAB基因相应片段，在核苷酸序列上具有很高的同源性。结论：本研究表明在肺炎克雷伯菌中有类似大肠埃希菌的acrAB基因存在，其表达水平决定了多重耐药表型。

Distribution and expression of active effux pump acrAB in clinical isolates of Klebsiella Pneumoniae

To study the mechanism of multidrug resistance in c1inical isolates of Klebsiella pneumoniae and detect the dis-tribution and expression of active efflux pump gene acrAB, homologous to that in Escherichia coli. Methods: The distribution ofacrAB in clinical strains and the standard strain (ATCC 10031) of Klebsiella pneumoniae was determined by PCR, and the 1evel ofmRNA expressions of acrAB by RT-PCR. We also analyzed the nucleotide sequence of acrAB section amplified by PCR in K. pneu-moniae ATCC 10031, and compared with the corresponding sequence of acrAB gene in Escherchia coli. Results: arcAB gene ho-mologous to that in Escherichia coli was found in all clinical strains of K. Pneumoniae and ATCC 10031. The levels of mRNA ex-pression of acrAB in multidrug-resistant (MDR) strains were significant1y higher than those in wild susceptible strains and in strainswith different resistance patterns(P < 0.01 ). But those in strains with different resistance patterns were only a little higher thanthose in wild susceptible strains (P< 0.05). There was high degree of homology in nucleotide sequence between the PCR expandedATCC 10031 acrAB gene sections and the corresponding ones in Escherichia coli. Conclusions: The study indicates that acrAB genehomologous to that in Escherchia coli is present in Klebsiellla pneumoniae, and its level of expression determines the multiple-resis-tant phenotype of the bacteria.