Interplay of efflux system, ampC, and oprD expression in carbapenem resistance of Pseudomonas aeruginosa clinical isolates
Interplay of efflux system, ampC, and oprD expression in carbapenem resistance of Pseudomonas aeruginosa clinical isolates
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DOI：
10.1128/aac.50.5.1633-1641.2006
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发表时间：
2006-05-01
影响因子：
4.9
通讯作者：
Landman, D
中科院分区：
文献类型：
--
作者：
Quale, J;Bratu, S;Landman, D
碳青霉烯类是治疗多重耐药铜绿假单胞菌感染的重要药物;碳青霉烯类耐药性的发展阻碍了有效的治疗选择。为了评估导致耐药的机制，分析了33株具有不同程度碳青霉烯类药物敏感性的临床分离株的染色体β-内酰胺酶（ampC）、对碳青霉烯类药物进入非常重要的孔蛋白（oprD）以及参与四种外排系统（mexA、mexC、mexE和mexX）的蛋白质的表达。使用每个靶基因的引物和荧光探针进行实时逆转录酶PCR。还进行了调节基因（ampR、mexR、nalC、nalD、mexT和mexZ）的测序。oprD的表达减少存在于所有亚胺培南和美罗培南耐药菌株中，但不是厄他培南耐药所必需的。在对碳青霉烯类抗生素明显耐药的几个分离株中未观察到ampC表达增加。在许多碳青霉烯类耐药分离株中观察到几种外排系统的表达增加。外排活性增加与厄他培南高水平耐药相关，并降低对美罗培南和氨曲南的敏感性。mexA表达增加的大多数分离株具有影响nalC和/或nalD的突变。两个分离株突变导致提前终止密码子在mexZ的mexX的表达显着升高，虽然mexZ的突变是不是一个先决条件过表达。铜绿假单胞菌临床分离株中的β-内酰胺耐药性是oprD产生减少、ampC活性增加和几种外排系统之间相互作用的结果。
Carbapenems are important agents for the therapy of infections due to multidrug-resistant Pseudomonas aeruginosa; the development of carbapenem resistance hampers effective therapeutic options. To assess the mechanisms leading to resistance, 33 clinical isolates with differing degrees of carbapenem susceptibility were analyzed for the expression of the chromosomal beta-lactamase (ampC), the porin that is important for the entry of carbapenems (oprD), and the proteins involved in four efflux systems (mexA, mexC, mexE, and mexX). Real-time reverse transcriptase PCR was performed using primers and fluorescent probes for each of the target genes. The sequencing of regulatory genes (ampR, mexR, nalC, nalD, mexT, and mexZ) was also performed. Diminished expression of oprD was present in all imipenem- and meropenem-resistant isolates but was not required for ertapenem resistance. Increased expression of ampC was not observed in several isolates that were overtly resistant to carbapenems. Increased expression of several efflux systems was observed in many of the carbapenem-resistant isolates. Increased efflux activity correlated with high-level ertapenem resistance and reduced susceptibility to meropenem and aztreonam. Most isolates with increased expression of mexA had mutations affecting nalC and/or nalD. Two isolates with mutations leading to a premature stop codon in mexZ had markedly elevated mexX expressions, although mutations in mexZ were not a prerequisite for overexpression. beta-Lactam resistance in clinical isolates of P. aeruginosa is a result of the interplay between diminished production of oprD, increased activity of ampC, and several efflux systems.