摘要

多药外排系统有助于细菌中的抗微生物抗性和致病性。在这里，我们报告了转录调节因子AcrR的鉴定和表征，控制尚未表征的多药外排泵，AcrAB在医院不动杆菌中。计算机分析显示AcrR和AcrAB的同源物在许多其他细菌物种的基因组中报道。我们证实编码AcrAB外排泵，acrA和acrB的基因形成多顺反子操纵子，其在acrA上游的acrR基因的控制下。生物信息学分析表明在acrAB操纵子的启动子区域中存在AcrR结合基序，并且通过电泳迁移率变动分析（EMSA）证实了AcrR的特异性结合。 EMSA数据显示AcrR与acrA起始密码子上游的-89bp结合。 mRNA表达分析表明，与野生型相比，缺失突变体中acrA和acrB基因的表达升高，证实AcrR在A.nosocomialis中充当acrAB操纵子的阻遏物。 acrR的缺失导致A.nosocomialis中的运动性，生物膜/薄膜形成和侵入增加。我们使用鼠模型进一步分析了AcrR在体内对A.nosocomialis发病机制中的作用，并且显示acrR突变体是高度毒力的，诱导小鼠的严重感染导致宿主死亡。此外，与野生型相比，acrR突变体的细胞内存活率更高。我们的数据表明AcrR作为AcrAB外排泵的重要调节剂起作用，并且与A.nosocomialis中的几种表型相关，例如运动性，生物膜/薄膜形成和发病机理。

Multidrug efflux systems contribute to antimicrobial resistance and pathogenicity in bacteria. Here, we report the identification and characterization of a transcriptional regulator AcrR controlling the yet uncharacterized multidrug efflux pump, AcrAB in Acinetobacter nosocomialis. In silico analysis revealed that the homologs of AcrR and AcrAB are reported in the genomes of many other bacterial species. We confirmed that the genes encoding the AcrAB efflux pump, acrA and acrB forms a polycistronic operon which is under the control of acrR gene upstream of acrA. Bioinformatic analysis indicated the presence of AcrR binding motif in the promoter region of acrAB operon and the specific binding of AcrR was confirmed by electrophoretic mobility shift assay (EMSA). The EMSA data showed that AcrR binds to -89 bp upstream of the start codon of acrA. The mRNA expression analysis depicted that the expression of acrA and acrB genes are elevated in the deletion mutant compared to that in the wild type confirming that AcrR acts as a repressor of acrAB operon in A. nosocomialis. The deletion of acrR resulted in increased motility, biofilm/pellicle formation and invasion in A. nosocomialis. We further analyzed the role of AcrR in A. nosocomialis pathogenesis in vivo using murine model and it was shown that acrR mutant is highly virulent inducing severe infection in mouse leading to host death. In addition, the intracellular survival rate of acrR mutant was higher compared to that of wild type. Our data demonstrates that AcrR functions as an important regulator of AcrAB efflux pump and is associated with several phenotypes such as motility, biofilm/pellicle formation and pathogenesis in A. nosocomialis.

https://www.ncbi.nlm.nih.gov/pubmed/30131944