Wolter Daniel J, Smith-Moland Ellen, Goering Richard V, Hanson Nancy D, Lister Philip D
Center for Research in Anti-Infectives and Biotechnology, Creighton University School of Medicine, Omaha, NE, USA.
Diagn Microbiol Infect Dis. 2004 Sep;50(1):43-50. doi: 10.1016/j.diagmicrobio.2004.05.004.
Fluoroquinolones and carbapenems are important drug classes used for the treatment of Pseudomonas aeruginosa infections. However, overexpression of the P. aeruginosa efflux pump, MexEF-OprN, can provide dual resistance to both fluoroquinolones and carbapenems. Recently, a hospital in Texas encountered several P. aeruginosa isolates resistant to both of these drug classes. The purpose of this study was to determine whether the mechanism responsible for this multidrug resistance involved the overexpression of MexEF-OprN. To test this hypothesis, 7 clinical isolates from the Texas hospital were analyzed for clonality, antimicrobial susceptibility, expression of the porin, oprD, and four multidrug-resistant efflux pumps (mexAB-oprM, mexCD-oprJ, mexEF-oprN, and mexXY), quinolone resistance-determining region mutations, and beta-lactamase production. Two groups of isolates possessed similar pulse field gel electrophoresis patterns indicating their genetic relatedness. In addition to fluoroquinolone and carbapenem resistance, each isolate also displayed varying degrees of susceptibility to additional beta-lactams tested and resistance to gentamicin. Interestingly, none of the 7 clinical isolates overexpressed mexEF-oprN as determined by semiquantitative reverse transcriptase polymerase chain reaction, but overexpression of mexXY was observed in 6 of the 7 isolates. All 7 isolates showed a decrease of OprD in the outer membrane and a reduction in transcriptional expression of oprD compared to wild-type strain, PAO1. These results demonstrate that multidrug resistance to the fluoroquinolones and carbapenems in these clinical isolates was not a result of the overexpression of the mexEF-oprN pump. Instead, resistance to these two agents seemed to arise through independent mutational events.
氟喹诺酮类和碳青霉烯类是用于治疗铜绿假单胞菌感染的重要药物类别。然而，铜绿假单胞菌外排泵MexEF - OprN的过表达可导致对氟喹诺酮类和碳青霉烯类药物产生双重耐药性。最近，德克萨斯州的一家医院遇到了几株对这两类药物均耐药的铜绿假单胞菌分离株。本研究的目的是确定导致这种多重耐药性的机制是否涉及MexEF - OprN的过表达。为了验证这一假设，对来自德克萨斯州医院的7株临床分离株进行了克隆性、抗菌药物敏感性、孔蛋白oprD以及四种多重耐药外排泵（mexAB - oprM、mexCD - oprJ、mexEF - oprN和mexXY）的表达、喹诺酮耐药决定区突变以及β - 内酰胺酶产生情况的分析。两组分离株具有相似的脉冲场凝胶电泳图谱，表明它们具有遗传相关性。除了对氟喹诺酮类和碳青霉烯类耐药外，每株分离株对其他测试的β - 内酰胺类药物也表现出不同程度的敏感性，并且对庆大霉素耐药。有趣的是，通过半定量逆转录聚合酶链反应测定，7株临床分离株中没有一株MexEF - OprN过表达，但在7株分离株中有6株观察到MexXY过表达。与野生型菌株PAO1相比，所有7株分离株在外膜中的OprD均减少，且oprD的转录表达降低。这些结果表明，这些临床分离株对氟喹诺酮类和碳青霉烯类的多重耐药性不是MexEF - OprN泵过表达的结果。相反，对这两种药物的耐药性似乎是通过独立的突变事件产生的。
