Preliminary Study On Inhibition Of The Staphylococcus Aureus Regulator SarA By Andrographolide

Staphylococcus aureus is one of the most prominent pathogens of nosocom ial- and community acquired bacterial infections around the world. It can cause a wide range of diseases, such as pneumonia, mastitis, osteomyelitis, endocard itis, skin infections, abscesses, food poisoning, toxic shock syndrome and septic emia. However, due to the abuse of antibiotics, a large number of medicine-res istant strains appear, especially methicillin-resistant Staphylococcus aureus(meth icillin-resistant Staphylococcus aureus, MRSA). MRSA is found to be resisitant to most of clinical medince even vancomycin. Due to bacterial drug resistance,the number of antibiotics we can choose is fewer, which is imperative to find new antibacterial targets and the corresponding inhibitors, a hopeful way to ef fectively solve the problem of serious bacterial drug resistance today.Staphylococcus aureus SarA, a global transcriptional regulator protein, can directly regulate virulence factors, and is closely related to bacteria biological membrane, adhesion and hemolysis. Therefore, SarA has been regarded as a ne w target and screening of its traditional Chinese medicine monomer inhibitor h as become a hotspot in current research. In this study, S. aureus SarA gene w as cloned, espressed and purified, using fluorescence recovery essay and real-ti me fusion experiments and phenotypic assays to research against the effect of S. aureus SarA.Andrographis is a diterpene lactones,which comes from a wide sources, using fluorescence recovery assay and Real-time dissolution test, Andrographolide showed good inhibitory activity on SarA, which was then evaluated through Biofilm test, Protein binding test and Hemolysis test. Furthermore, animal experiment was carried out to study wheather Andrographis plays an effective role in vivo. The results showed that andrographolide significantly inhibited biofilm formation by reducing the activity of SarA. When the concentration of andrographolide was 800μg/ml,the Biofilm inhibition rate was 78.7±1.7%. The results of Protein binding assay indicated that different concentrations of andro influence adhesion differently and in a dose dependently. The treatment of the WT strain with 256μg/ml AP was measured and the adhesion rate was 53.3±1.5%. While Hemolysis test results showed that S. aureus treated with 16μg/ml andrographolide,the hemolysis rate was 36.6 ± 5.1%. The results further verify the activity of andrographolide which can inhibit activity of Staphylococcus aureus SarA. Moreever, animal experiments demonstrated that andrographolide has a therapeutic effects on the abscess model of S.aureus and mortality. In summary, Andrographolide,as a lead compound of SarA targeting medicine,provide new insights and theoretical basis for the subsequent design of research and development of new drugs.