Iwalokun B A, Akinloye O, Udoh B E, Akinyemi K O
a Molecular Biology & Biotechnology Department , Nigerian Institute of Medical Research , Lagos , Nigeria.
b Clinical Chemistry and Molecular Diagnostic Research Laboratory, Department of Medical Laboratory Science, College of Medicine , University of Lagos , Lagos , Nigeria.
J Immunoassay Immunochem. 2019;40(2):214-236. doi: 10.1080/15321819.2018.1555765. Epub 2019 Jan 29.
Multidrug resistant (MDR) S. aureus infections continue to account for excess mortality in hospital and community settings and constitute a rising global health problem. However, data on the efficacy and mechanism of actions of alternative solutions like silver nanoparticles in developing countries are lacking. This study investigated anti-staphylococcal activity of silver nanoparticles (AgNP) against local strains from Nigeria. A total 119 clinical isolates of S. aureus from five Nigerian laboratories categorized as MRSA (n = 52) and MSSA (n = 67) by PCR were studied. The MIC of AgNP produced by chemical reduction method and characterized by surface plasmon resonance absorbance and size equivalence by scanning electron microscopy was determined by microbroth dilution method. Its effect on protease activity and plasmids were also investigated. Baseline characteristics of the isolates revealed MDR phenotype of the isolates, carriage of diverse plasmids (15-32 kb) among the MDR MSSA, and mean extracellular protease activity of 24.8-55.7 U/mL. The chemically synthesized AgNP had a peak absorbance at 400 nm with a size equivalence of 4.58 nm. The MICs of AgNP against the isolates were 4.7 μg/mL and 4.9 μg/mL, respectively, for MRSA and MSSA (P > 0.05). The bactericidal effect of AgNP at 2.5-5 μg/mL on the MSSA and MRSA isolates was observed at 2.7-5.5 h post exposure in vitro. Further analysis revealed plasmid eviction in the MDR MSSA isolates exposed to 5 μg/mL AgNP and dose-dependent reduction in extracellular protease activity by 84.6-93.1%. Hemolysis of human erythrocytes by AgNP was not observed at the MIC range. Conclusion: This study revealed safety and efficacy of AgNP against clinical MDR S. aureus isolates from Nigeria, using plasmid eviction and protease inhibition as mechanisms of action.
多重耐药（MDR）金黄色葡萄球菌感染在医院和社区环境中持续导致过高的死亡率，构成了一个日益严重的全球健康问题。然而，在发展中国家，关于银纳米颗粒等替代解决方案的疗效和作用机制的数据却很缺乏。本研究调查了银纳米颗粒（AgNP）对来自尼日利亚的本地菌株的抗葡萄球菌活性。通过聚合酶链反应（PCR）对来自尼日利亚五个实验室的总共119株金黄色葡萄球菌临床分离株进行了研究，这些分离株被分类为耐甲氧西林金黄色葡萄球菌（MRSA，n = 52）和甲氧西林敏感金黄色葡萄球菌（MSSA，n = 67）。通过化学还原法制备并通过表面等离子体共振吸光度和扫描电子显微镜确定尺寸等效性来表征的AgNP的最低抑菌浓度（MIC），采用微量肉汤稀释法进行测定。还研究了其对蛋白酶活性和质粒的影响。分离株的基线特征显示出分离株的多重耐药表型、多重耐药MSSA中存在多种质粒（15 - 32 kb）以及平均细胞外蛋白酶活性为24.8 - 55.7 U/mL。化学合成的AgNP在400 nm处有一个峰值吸光度，尺寸等效值为4.58 nm。AgNP对分离株的MIC分别为，MRSA为4.7 μg/mL，MSSA为4.9 μg/mL（P > 0.05）。在体外接触后2.7 - 5.5小时观察到2.5 - 5 μg/mL的AgNP对MSSA和MRSA分离株的杀菌作用。进一步分析显示，暴露于5 μg/mL AgNP的多重耐药MSSA分离株中质粒被清除，并且细胞外蛋白酶活性呈剂量依赖性降低84.6 - 93.1%。在MIC范围内未观察到AgNP对人红细胞的溶血作用。结论：本研究揭示了AgNP对来自尼日利亚的临床多重耐药金黄色葡萄球菌分离株具有安全性和有效性，其作用机制为质粒清除和蛋白酶抑制。
