School of Postgraduate Studies, International Medical University, Kuala Lumpur, Malaysia.
Division of Applied Biomedical Sciences and Biotechnology, School of Health Sciences, International Medical University, Kuala Lumpur, Malaysia.
PLoS One. 2019 Feb 28;14(2):e0213079. doi: 10.1371/journal.pone.0213079. eCollection 2019.
Staphylococcus epidermidis, is a common microflora of human body that can cause opportunistic infections associated with indwelling devices. It is resistant to multiple antibiotics necessitating the need for naturally occurring antibacterial agents. Malaysian propolis, a natural product obtained from beehives exhibits antimicrobial and antibiofilm properties. Chitosan-propolis nanoparticles (CPNP) were prepared using Malaysian propolis and tested for their effect against S. epidermidis. The cationic nanoparticles depicted a zeta potential of +40 and increased the net electric charge (zeta potential) of S. epidermidis from -17 to -11 mV in a concentration-dependent manner whereas, ethanol (Eth) and ethyl acetate (EA) extracts of propolis further decreased the zeta potential from -17 to -20 mV. Confocal laser scanning microscopy (CLSM) depicted that CPNP effectively disrupted biofilm formation by S. epidermidis and decreased viability to ~25% compared to Eth and EA with viability of ~60-70%. CPNP was more effective in reducing the viability of both planktonic as well as biofilm bacteria compared to Eth and EA. At 100 μg/mL concentration, CPNP decreased the survival of biofilm bacteria by ~70% compared to Eth or EA extracts which decreased viability by only 40%-50%. The morphology of bacterial biofilm examined by scanning electron microscopy depicted partial disruption of biofilm by Eth and EA extracts and significant disruption by CPNP reducing bacterial number in the biofilm by ~90%. Real time quantitative PCR analysis of gene expression in treated bacteria showed that genes involved in intercellular adhesion such as IcaABCD, embp and other related genes were significantly downregulated by CPNP. In addition to having a direct inhibitory effect on the survival of S. epidermidis, CPNP showed synergism with the antibiotics rifampicin, ciprofloxacin, vancomycin and doxycycline suggestive of effective treatment regimens. This would help decrease antibiotic treatment dose by at least 4-fold in combination therapies thereby opening up ways of tackling antibiotic resistance in bacteria.
表皮葡萄球菌是人体常见的微生物菌群，可引起与留置装置相关的机会性感染。它对多种抗生素具有耐药性，因此需要使用天然存在的抗菌剂。马来西亚蜂胶是一种从蜂巢中提取的天然产物，具有抗菌和抗生物膜特性。壳聚糖-蜂胶纳米粒子（CPNP）是用马来西亚蜂胶制备的，并测试其对表皮葡萄球菌的作用。阳离子纳米粒子的表面电位为+40，并以浓度依赖的方式将表皮葡萄球菌的净电荷（表面电位）从-17 增加到-11 mV，而蜂胶的乙醇（Eth）和乙酸乙酯（EA）提取物则进一步将表面电位从-17 降低到-20 mV。共聚焦激光扫描显微镜（CLSM）显示，CPNP 可有效破坏表皮葡萄球菌生物膜的形成，并使细胞活力降低至约 25%，而 Eth 和 EA 则使细胞活力降低至约 60-70%。与 Eth 和 EA 相比，CPNP 更有效地降低浮游和生物膜细菌的活力。在 100 μg/mL 浓度下，CPNP 使生物膜细菌的存活率降低了约 70%，而 Eth 或 EA 提取物仅降低了 40%-50%的存活率。扫描电子显微镜检查细菌生物膜的形态显示，Eth 和 EA 提取物部分破坏了生物膜，而 CPNP 则显著破坏了生物膜，使生物膜中的细菌数量减少了约 90%。用处理过的细菌进行实时定量 PCR 分析基因表达显示，细胞间黏附相关基因如 IcaABCD、embp 和其他相关基因的表达显著下调。CPNP 不仅对表皮葡萄球菌的存活有直接抑制作用，还与抗生素利福平、环丙沙星、万古霉素和强力霉素表现出协同作用，提示有效的治疗方案。这将有助于在联合治疗中至少将抗生素治疗剂量减少 4 倍，从而为解决细菌的抗生素耐药性开辟途径。
