Scool of Medicine, Iran University of Medical Science, Tehran, Iran.
International Campus, Iran University of Medical Science, Tehran, Iran.
J Basic Microbiol. 2023 Jun;63(6):632-645. doi: 10.1002/jobm.202200612. Epub 2023 Jan 19.
The emergence of multidrug-resistant (MDR) strains of Klebsiella pneumoniae is associated with high morbidity and mortality due to limited treatment options. This study attempts to biologically synthesize silver nanoparticles (AgNPs) and investigate their effect on expression levels of virulence and biofilm-related genes in clinically isolated K. pneumoniae. In this study, biofilm formation ability, antibiotic resistance pattern, extended-spectrum β-lactamases (ESBLs), and carbapenemases production were investigated for 200 clinical isolates of K. pneumoniae using phenotypic methods. Polymerase chain reaction (PCR) was used to detect virulence and biofilm-related genes, ESBL-encoding genes, and carbapenem resistance genes. AgNPs were synthesized using the bio-reduction method. The antibacterial effects of AgNPs were investigated by microdilution broth. In addition, the cytotoxic effect of AgNPs on L929 fibroblast cell lines was determined. The effects of AgNPs on K. pneumoniae virulence and biofilm-related genes (fimH, rmpA, and mrkA) were determined using quantitative real-time PCR. Thirty percent of the isolates produced a strong biofilm. The highest and lowest levels of resistance were observed against amoxicillin/clavulanic acid (95.4%) and tigecycline (96%), respectively. About 31% of isolates were considered positive for carbapenemases, and 75% of the isolates produced an ESBLs enzyme. Different frequencies of mentioned genes were observed. The synthesized AgNPs had a spherical morphology and varied in size. AgNPs inhibited the growth of MDR K. pneumoniae at 128 µg/ml. In addition, AgNPs downregulated the expression of fimH, rmpA, and mrkA genes by 10, 7, and 14-fold, respectively (p < 0.05), also exerted no cytotoxic effect on L929 fibroblast cell lines. It was revealed that AgNPs lead to a decrease in expression levels of virulence and biofilm-related genes; therefore, it was concluded that AgNPs had an excellent antibacterial effect on MDR K. pneumoniae.
产多药耐药（MDR）肺炎克雷伯菌的出现与治疗选择有限导致的高发病率和死亡率有关。本研究试图通过生物合成法合成银纳米粒子（AgNPs），并研究其对临床分离的肺炎克雷伯菌毒力和生物膜相关基因表达水平的影响。本研究采用表型方法检测了 200 株临床分离的肺炎克雷伯菌的生物膜形成能力、抗生素耐药模式、超广谱β-内酰胺酶（ESBLs）和碳青霉烯酶的产生。聚合酶链反应（PCR）用于检测毒力和生物膜相关基因、ESBL 编码基因和碳青霉烯耐药基因。采用生物还原法合成 AgNPs。采用微量稀释肉汤法研究 AgNPs 的抗菌作用。此外，还测定了 AgNPs 对 L929 成纤维细胞系的细胞毒性作用。采用实时荧光定量 PCR 法测定 AgNPs 对肺炎克雷伯菌毒力和生物膜相关基因（fimH、rmpA 和 mrkA）的影响。30%的分离株产生强生物膜。对阿莫西林/克拉维酸（95.4%）和替加环素（96%）的耐药率最高和最低。约 31%的分离株被认为产碳青霉烯酶阳性，75%的分离株产生 ESBLs 酶。观察到不同频率的上述基因。合成的 AgNPs 呈球形，大小不一。AgNPs 在 128μg/ml 时抑制 MDR 肺炎克雷伯菌的生长。此外，AgNPs 使 fimH、rmpA 和 mrkA 基因的表达分别下调 10、7 和 14 倍（p<0.05），对 L929 成纤维细胞系也没有细胞毒性作用。结果表明，AgNPs 导致毒力和生物膜相关基因表达水平降低，因此得出结论，AgNPs 对 MDR 肺炎克雷伯菌具有良好的抗菌作用。
