冬凌草甲素对金黄色葡萄球菌生物膜的抑制机制

Inhibition of Staphylococcus aureus biofilm formation by oridonin

摘要:

【背景】金黄色葡萄球菌是一种常见的食源性致病菌，易在食品及加工器具表面形成生物膜，引起食品腐败和疾病的传播，威胁食品安全。【目的】研究冬凌草甲素抑制金黄色葡萄球菌生物膜形成的作用机制。【方法】使用结晶紫染色法和扫描电镜观察冬凌草甲素对金黄色葡萄球菌生物膜形成的抑制作用，刚果红平板法定性检测冬凌草甲素对细胞间多糖黏附素(polysaccharide intercellular adhesion，PIA)合成的影响，分光光度法测定冬凌草甲素对供试菌株胞外DNA (eDNA)释放量的影响，RT-PCR技术检测冬凌草甲素对供试菌株icaA、cidA、agrA和sarA基因表达量的影响。【结果】冬凌草甲素对金黄色葡萄球菌生物膜形成有较强的抑制作用；冬凌草甲素能显著抑制PIA的合成，且呈浓度剂量依赖；冬凌草甲素能抑制供试菌株eDNA的释放量，其中1/4最小抑菌浓度(minimum inhibitory concentration，MIC)的冬凌草甲素作用金黄色葡萄球菌16 h后，与对照组相比，eDNA的释放量降低了48.62%；冬凌草甲素可显著抑制金黄色葡萄球菌生物膜形成相关基因的表达，其中1/2MIC的冬凌草甲素作用金黄色葡萄球菌16 h后，icaA、cidA、agrA和sarA基因的表达量分别比对照降低了91.6%、94.7%、77.6%和70.4%。【结论】冬凌草甲素通过抑制icaA和cidA基因的表达，影响PIA的合成和eDNA的释放，进而干预生物膜的形成。

Abstract:

[Background] Staphylococcus aureus is a type of common food-borne pathogenic bacteria that can easily form biofilm on the surface of food and processing equipment, leading to food corruption and disease spread, and threatening food safety. [Objective] To study the inhibition of S. aureas biofilm formation by oridonin. [Methods] The inhibition of biofilm formation by oridonin was studied using crystal violet staining assay and scanning electron microscopy. The influence of oridonin on the formation of polysaccharide intercellular adhesion and the release of extracellular DNA (eDNA) was detected by Congo red agar and spectrophotometer. RT-PCR analysis was used to determine the effect of oridonin on the expression of genes, including icaA, cidA, agrA and sarA. [Results] Oridonin showed strong antimicrobial activity on S. aureas biofilm formation. Polysaccharide intercellular adhesion formation and eDNA release were greatly inhibited by oridonin. eDNA release decreased by 48.62% after incubated with oridonin at 1/4MIC for 16 h. Oridonin could significantly inhibit the expression of biofilm forming related genes in S. aureas. After incubated with of oridonin at 1/2MIC for 16 h, the relative expression of icaA, cidA, agrA and sarA of S. aureas were reduced by 91.6%, 94.7%, 77.6% and 70.4%, respectively. [Conclusion] Oridonin can significantly inhibit the biofilm formation of S. aureas via the reduction of icaA and cidA expression, so as to influence the synthesis of polysaccharide intercellular adhesion and the eDNA release.