纳米银的抗菌特性及对多重耐药菌株的抗菌作用

Antibacterial activity of silver nanoparticles against multiple drug resistant strains

摘要:

[目的]利用革兰氏阴性细菌、革兰氏阳性细菌和真菌的模式菌株分析纳米银的抗菌特性，并评价纳米银对多重耐药菌株的抗菌作用。[方法]利用生物法合成的纳米银，以微量肉汤法测定3种标准菌株的最小抑菌浓度（MIC）和最小杀菌浓度（MBC），并计算MBC/MIC比值。用系列浓度的纳米银处理3株标准菌株后经平板计数法绘制时间-杀菌曲线。采用菌落平板计数法测定了纳米银对3种标准菌株的“抗生素后效应”（post-antibiotic effect，PAE），最后在生物安全II级实验室测定纳米银对临床分离的多重耐药菌株的抗菌作用。[结果]用生物法合成了粒径5-30 nm的纳米银，zeta电位为-19.5 mV。该纳米银制剂对3种标准菌株的时间-杀菌曲线均表现为时间依赖型抗菌作用。纳米银对大肠杆菌和白色念珠菌“抗生素后效应”随着浓度增加而增加，对金黄色葡萄球菌无明显“抗生素后效应”。纳米银对3种标准菌株的MIC值和MBC值均在1.00-4.00 μg/mL之间；对3株人源性多重耐药菌MIC值在6.00-26.00 μg/mL之间，MBC值在1.00-32.00 μg/mL之间；对14株动物源性多重耐药菌MIC值在4.00-10.00 μg/mL之间，MBC值在8.00-16.00 μg/mL之间。纳米银对所有测试菌株的MBC/MIC值均小于2。[结论]纳米银是一种时间依赖型的抗菌剂，有不同程度的“抗生素后效应”，对人源和动物源性多重耐药菌有杀菌作用。

关键词:纳米银(silver nanoparticles;AgNPs);最小抑菌浓度(MIC);最小杀菌浓度(MBC);时间-杀菌曲线;抗生素后效应

Abstract:

[Objective] The objective of the study was to assess the antimicrobial activity of silver nanoparticles (AgNPs) against multiple drug resistant strains. [Methods] Minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of AgNPs against three model microbes, namely Escherichia coli, Staphylococcus aureus, Candida albicans were measured by microdilution broth method. Time-kill curve within 24 h was made according to colony count method after three model microbes were treated with a series concentration of AgNPs. Post-antibiotic effect was tested by colony count method. Finally, we determined the antimicrobial efficacy against multiple drug resistant strains in biological safety laboratory grade 2 (BSL-2). [Results] AgNPs with a diameter of 5 nm to 30 nm were synthesized by the biological method. The zeta potential was -19.5 mV. The time-kill curve of the three model microbes showed time-dependent antibacterial activity. The effect of AgNPs on E. coli and C. albicans after "antibiotic effect" increased with time, there was no obvious "post-antibiotic effect" on S. aureus. Both MIC values and MBC values of AgNPs for the three model microbes were between 1 μg/mL and 4 μg/mL. However, the MIC value of AgNPs for the three human multidrug-resistant strains was 6 μg/mL to 26 μg/mL and MBC value of AgNPs was 10 μg/mL to 32 μg/mL. The MIC values of AgNPs for 14 animal multi-drug resistant strains were between 4 μg/mL and 10 μg/mL, and the MBC values were between 8 μg/mL and 16 μg/mL. The MBC/MIC values of all the tested strains were less than 2. [Conclusion] AgNPs is a time-dependent antimicrobial agent with different "post-antibiotic effect", which can inhibit both human and animal-derived multi-drug resistant bacteria.

Key words:silver nanoparticles (AgNPs);minimal inhibitory concentration;minimum bactericidal concentration;time-kill curve;post-antibiotic effect