This study was carried out to investigate the possible efflux pump inhibitory activity of biologically synthesized silver nanoparticles (AgNPs) against multidrug‐resistant (MDR) Acinetobacter baumannii isolates. In this study, the physicochemical characteristics of synthesized AgNPs were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), and Fourier transform infrared spectrophotometer (FTIR) methods. Subsequently, MDR A. baumannii isolates were recovered from clinical samples and the phenotypic cartwheel efflux assay and polymerase chain reaction (PCR) were used to elucidate the possible presence of efflux pump in MDR strains. After treatment of MDR strains with sub‐minimum inhibitory concentration (MIC) concentration of AgNPs, the expression level of efflux pump genes was evaluated using a quantitative real‐time PCR technique. The synthesized AgNPs had a spherical nanostructure, with mean size 38.89 nm, according to SEM and TEM data. XRD and FTIR results confirmed the synthesis of AgNPs. The results of PCR revealed that among 50 strains, 12 A. baumannii strains had efflux pump genes and the expression level of AdeA, AdeC, AdeS, AdeR, AdeI, AdeJ, and AdeK efflux pump genes was downregulated significantly after the treatment with AgNPs. In addition, the inhibitory effect of AgNPs on efflux pumps can be detected when the MIC of ethidium bromide (EtBr) with AgNPs is lower than that of EtBr alone. According to the results, the biologically synthesized AgNPs exhibit efflux pumps inhibitory activity, which may be one of the possible mechanisms of their antibacterial activity against MDR A. baumannii strains.

中文翻译：

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生物合成银纳米粒子对多重耐药鲍曼不动杆菌临床分离株的外排泵抑制活性

本研究旨在研究生物合成的银纳米粒子 (AgNPs) 对多重耐药 (MDR) 鲍曼不动杆菌分离株的外排泵抑制活性。在这项研究中，使用扫描电子显微镜 (SEM)、透射电子显微镜 (TEM)、X 射线衍射 (XRD) 和傅里叶变换红外分光光度计 (FTIR) 方法研究了合成的 AgNPs 的理化特性。随后，从临床样本中回收了耐多药鲍曼不动杆菌分离株，并使用表型车轮外排试验和聚合酶链反应 (PCR) 来阐明多药耐药菌株中可能存在的外排泵。用亚最低抑菌浓度 (MIC) 浓度的 AgNPs 处理 MDR 菌株后，使用定量实时 PCR 技术评估外排泵基因的表达水平。根据 SEM 和 TEM 数据，合成的 AgNPs 具有球形纳米结构，平均尺寸为 38.89 nm。XRD 和 FTIR 结果证实了 AgNPs 的合成。PCR结果显示，50株鲍曼不动杆菌中，有12株具有外排泵基因，AgNPs处理后AdeA、AdeC、AdeS、AdeR、AdeI、AdeJ和AdeK外排泵基因的表达水平显着下调。此外，当溴化乙锭 (EtBr) 与 AgNPs 的 MIC 低于单独的 EtBr 时，可以检测到 AgNPs 对外排泵的抑制作用。根据结果​​，生物合成的 AgNPs 表现出外排泵抑制活性，