Abstract：
Long-term administration of certain macrolides is efficacious in patients with persistent pulmonary Pseudomonas aeruginosa infection, despite how limited the clinically achievable concentrations are, being far below their MICs. An increase in the sub-MIC of macrolide exposure-dependent sensitivity to nitrosative stress is a typical characteristic of P. aeruginosa. However, a few P. aeruginosa clinical isolates do not respond to sub-MIC of macrolide treatment. Therefore, we examined the effects of sub-MIC of erythromycin (EM) on the sensitivity to nitrosative stress together with an efflux pump inhibitor (EPI) phenylalanine arginyl β-naphthylamide (PAβN). The sensitivity to nitrosative stress increased, suggesting that the efflux pump was involved in inhibiting the sub-MIC of macrolide effect. Analysis using efflux pump-mutant P. aeruginosa revealed that MexAB-OprM, MexXY-OprM, and MexCD-OprJ are factors in reducing the sub-MIC of macrolide effect. Since macrolides interfere with quorum sensing (QS), we demonstrated that the QS-interfering agent furanone C-30 (C-30) producing greater sensitivity to nitric oxide (NO) stress than EM. The effect of C-30 was decreased by overproduction of MexAB-OprM. To investigate whether the increase in the QS-interfering agent exposure-dependent sensitivity to nitrosative stress is characteristic of P. aeruginosa clinical isolates, we examined the viability of P. aeruginosa treated with NO. Although treatment with EM could reduce cell viability, a high variability in EM effects was observed. Conversely, C-30 was highly effective at reducing cell viability. Treatment with both C-30 and PAβN was sufficiently effective against the remaining isolates. Therefore, the combination of a QS-interfering agent and an EPI could be effective in treating P. aeruginosa infections.
摘要：
某些大环内酯类药物的长期给药对持续肺部铜绿假单胞菌感染的患者是有效的，尽管临床上可达到的浓度有限，远远低于他们的中等收入国家。大环内酯暴露依赖性亚硝化应激敏感性的亚MIC增加是铜绿假单胞菌的典型特征。然而,一些铜绿假单胞菌临床分离株对大环内酯治疗的亚MIC无反应。因此,我们研究了红霉素（EM）的亚MIC对亚硝化应激敏感性的影响以及外排泵抑制剂（EPI）苯丙氨酸精氨酰β-萘酰胺（PAβN）。对亚硝化胁迫的敏感性增加，表明外排泵参与抑制大环内酯作用的亚MIC。使用外排泵突变的铜绿假单胞菌分析显示，MexAB-OprM，MexXY-OprM,和MexCD-OprJ是降低大环内酯作用亚MIC的因素。由于大环内酯类会干扰群体感应(QS)，我们证明了QS干扰剂呋喃酮C-30（C-30）比EM对一氧化氮（NO）应激产生更大的敏感性。C-30的作用因MexAB-OprM的过量产生而降低。为了研究QS干扰剂暴露依赖性亚硝基应激敏感性的增加是否是铜绿假单胞菌临床分离株的特征，我们检查了用NO处理的铜绿假单胞菌的活力。尽管用EM治疗可以降低细胞活力，观察到EM效应的高度变异性。相反，C-30在降低细胞活力方面非常有效。用C-30和PAβN处理对剩余的分离株足够有效。因此,QS干扰剂和EPI的组合可有效治疗铜绿假单胞菌感染。
