Li Xian-Zhi, Poole Keith, Nikaido Hiroshi
Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3206, USA.
Antimicrob Agents Chemother. 2003 Jan;47(1):27-33. doi: 10.1128/AAC.47.1.27-33.2003.
Of the six putative small multidrug resistance (SMR) family proteins of Pseudomonas aeruginosa, a protein encoded by the PA4990 gene (emrE(Pae)) shows the highest identity to the well-characterized EmrE efflux transporter of Escherichia coli. Reverse transcription-PCR confirmed the expression of emrE(Pae) in the wild-type strain of P. aeruginosa. Using isogenic emrE(Pae), mexAB-oprM, and/or mexB deletion mutants, the contributions of the EmrE protein and the MexAB-OprM efflux system to drug resistance in P. aeruginosa were assessed by a drug susceptibility test carried out in a low-ionic-strength medium, Difco nutrient broth. We found that EmrE(Pae) contributed to intrinsic resistance not only to ethidium bromide and acriflavine but also to aminoglycosides. In this low-ionic-strength medium, MexAB-OprM was also shown to contribute to aminoglycoside resistance, presumably via active efflux. Aminoglycoside resistance caused by these two pumps could not be demonstrated in high-ionic-strength media, such as Luria broth or Mueller-Hinton broth. The EmrE-dependent efflux of ethidium bromide was confirmed by a continuous fluorescence assay.
在铜绿假单胞菌的六种假定的小多药耐药（SMR）家族蛋白中，由PA4990基因编码的一种蛋白（EmrE(Pae)）与已得到充分研究的大肠杆菌EmrE外排转运蛋白具有最高的同源性。逆转录聚合酶链反应证实了EmrE(Pae)在铜绿假单胞菌野生型菌株中的表达。使用同基因的EmrE(Pae)、mexAB-oprM和/或mexB缺失突变体，通过在低离子强度培养基（Difco营养肉汤）中进行药敏试验，评估了EmrE蛋白和MexAB-OprM外排系统对铜绿假单胞菌耐药性的贡献。我们发现EmrE(Pae)不仅对溴化乙锭和吖啶黄素，而且对氨基糖苷类药物都有固有耐药性。在这种低离子强度培养基中，MexAB-OprM也被证明对氨基糖苷类药物耐药有贡献，可能是通过主动外排。在高离子强度培养基如Luria肉汤或Mueller-Hinton肉汤中，无法证明这两种泵引起的氨基糖苷类药物耐药性。通过连续荧光测定法证实了溴化乙锭的EmrE依赖性外排。
