纳米银和二氧化钛对金黄色葡萄球菌核酸的影响

Inhibitory effects of nano silver and titanium dioxide on the nucleic acid of staphylococcus aureus

目的 研究纳米银（Ag）和二氧化钛（TiO2）两种无机抗菌剂对金黄色葡萄球菌核酸含量的影响，分析抗菌剂的抗菌作用机制。方法 制备牛肉膏蛋白胨液体培养基，分别测定纳米Ag和TiO2的最低抑菌浓度（MIC）；以1/2MIC纳米Ag和TiO2浓度作用于金黄色葡萄球菌的培养液，用紫外分光光度计检测培养液中从菌体漏出的DNA和DNA等大分子物质含量，确定抗菌剂对细菌细胞膜的损伤程度； 用荧光显微镜观察菌体荧光强度，确定菌体内核酸染色程度；并用荧光分光光度计测定荧光值，确定菌体内核酸DNA和RNA含量。结果 纳米Ag和TiO2对金黄色葡萄球菌的MIC值分别为5.781μg/ml和1.6mg/ml，以1/2MIC为作用浓度，纳米Ag组和TiO2组分别与对照组相比培养液上清液中漏出的DNA和DNA等大分子物质含量，结果显示没有明显差别（P〉0.05），菌体核酸染色荧光强度和DNA和RNA含量，结果显示纳米Ag组和TiO2组与对照组相比显著减少（P〈0.05或P〈0.01）。结论 纳米Ag比TiO2对金黄色葡萄球菌具有明显抗菌作用，纳米Ag比TiO2有更强的抗菌性能；纳米Ag和TiO2的抗菌机制可能与抑制了金黄色葡萄球菌核酸DNA和RNA的合成有关，从而抑制细菌蛋白合成，抑制细菌的生长。

Objective To study the effects of nano silver （Ag） and titanium dioxide （TiO2） on the content of nucleic acid in staphylococcus aureus in order to explore their antibacterial mechanisms. Methods After preparation of beef extract peptone liquid cultures, the effects of minimal inhibitory concentrations （MICs） of nano Ag and TiO2 on staphylococcus aureus strains were determined. With the 1/2 MICs nano Ag and TiO2, the contents of DNA and RNA macromolecules from staphylococcus aureus cultures were measured to determine the damage degree of staphylococcus aureus cell membranes by ultraviolet spectrophotometer, and then the fluorescence intensities of the staphylococcus aureus cells were observed under fluorescence microscope and the fluorescence values were tested by fluorescence spectrophotometer to determine the contents of nucleic acid DNA and RNA. Results The MICs of nano Ag and TiO2 were 1.6 mg/mL and 5.781μg/mL. After treatment with the 1/2 MICs nano Ag and TiO2, nano Ag group and TiO2 group were compared with the control group （culture fluid without adding antibacterial agent）, respectively, and there were no significant differences in the contents of DNA and RNA macromolecules from staphylococcus aureus cultures between n anoAg group and control group as well as between TiO2 group and control group were （P〉0.05）, and there were significant decreases in fluorescence intensities and the contents of nucleic acid DNA and RNA （P〈0.01）. Conclusions Nano Ag and TiO2 had obvious antibacterial effects on staphylococcus aureus and the antibacterial properties of nano Ag was stronger than that of TiO2. The antibacterial mechanisms of nano Ag and TiO2 against staphylococcus aureus may be associated with the inhibition of the synthesis of nucleic acid DNA and RNA, inhibiting protein synthesis and then bacterial growth.