Involvement of an active efflux system in the natural resistance of Pseudomonas aeruginosa to aminoglycosides
Involvement of an active efflux system in the natural resistance of Pseudomonas aeruginosa to aminoglycosides
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DOI：
10.1128/aac.43.11.2624
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发表时间：
1999-11-01
影响因子：
4.9
通讯作者：
Plésiat, P
中科院分区：
文献类型：
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作者：
Aires, JR;Köhler, T;Plésiat, P
铜绿假单胞菌PAO 1经Tn 501插入突变后，获得一株对氨基糖苷类、四环素类和红霉素敏感的突变株11B。克隆和测序实验表明，11B是缺乏，在那个时候，未知的主动外排系统，含有同源的MexAB。该位点还含有一个假定的调控基因，mexZ，转录发散外排操纵子。引入携带外排系统基因的重组质粒将11B的抗性恢复至亲本水平，而这些基因的过表达强烈增加了PAO 1宿主的底物抗生素的MIC。抗生素积累研究证实，这个新系统是一个能量依赖性主动外排系统，泵出氨基糖苷类。此外，该系统似乎与外膜蛋白OprM一起起作用。在撰写和综述本论文的同时，已经报道了具有与我们的泵基因（铜绿假单胞菌的mexXY）相同的序列的基因在大肠杆菌宿主中增加对红霉素、氟喹诺酮和有机阳离子的抗性，尽管没有检查氨基糖苷类的流出（Mine et al.抗菌剂探员凯莫特。43：415-417，1999）。因此，我们的研究表明，MexXY系统在铜绿假单胞菌对氨基糖苷类的内在耐药性中起着重要作用。尽管MexXY的过度表达增加了对氟喹诺酮类药物的耐药性水平，但铜绿假单胞菌中mexXY操纵子的破坏对这些药物的敏感性没有可检测的影响。
A mutant, named 11B, hypersusceptible to aminoglycosides, tetracycline, and erythromycin was isolated after Tn501 insertion mutagenesis of Pseudomonas aeruginosa PAO1. Cloning and sequencing experiments showed that 11B was deficient in an, at that time, unknown active efflux system that contains homologs of MexAB. This locus also contained a putative regulatory gene, mexZ, transcribed divergently from the efflux operon. Introduction of a recombinant plasmid that carries the genes of the efflux system restored the resistance of 11B to parental levels, whereas overexpression of these genes strongly increased the MICs of substrate antibiotics for the PAO1 host. Antibiotic accumulation studies confirmed that this new system is an energy-dependent active efflux system that pumps out aminoglycosides. Furthermore, this system appeared to function with an outer membrane protein, OprM. While the present paper was being written and reviewed, genes with a sequence identical to our pump genes, mexXY of P. aeruginosa, have been reported to increase resistance to erythromycin, fluoroquinolones, and organic cations in Escherichia coli hosts, although efflux of aminoglycosides was not examined (Mine et al., Antimicrob. Agents Chemother. 43:415-417, 1999). Our study thus shows that the MexXY system plays an important role in the intrinsic resistance of P. aeruginosa to aminoglycosides. Although overexpression of MexXY increased the level of resistance to fluoroquinolones, disruption of the mexXY operon in P. aeruginosa had no detectable effect on susceptibility to these agents.