A Preliminary Study On The Molecular Mechanism Of Sodium Houttuyfonate Inhibits Staphylococcus Aureus Biofilm

Staphylococcus aureus (S. aureus) which belongs to zoonotic pathogensendangering human health and livestock breeding, is a conditioned pathogendistributed around our living space. S. aureus can cause infection in differentorganizations of the body characterized by local inflammation or systemic syndromein clinic. Antibiotics are widely used in the infections induced by S. aureus. In recentyears, the infections induced by methicillin-resistant S. aureus (MRSA) have arousedwidespread attention. MRSA as a high pathogenicity bacteria, spreads widely, and hasa high resistance to antiseptics. Most antibiotics are not effective in the trestment ofthe infections induced by MRSA, which seriously endanger life once severe infectionoccurred. In addition, S. aureus can form biofilm in the infection, not only increasesthe resistance, but also cause repetitive infection or latent infection. Both increased inpatients with pain, and increases the difficulty of treatment. So more and morescientific researchers begin to pay attention to the research on S. aureus and biofilm.The research including all aspects of S. aureus and biofilm formation mechanism,regulation, drug resistance mechanism and new antibiotics discovery. Due to the richresources of Chinese herbal medicine, China has a unique advantages in the field ofnew antibiotic research. It is commonly thought that the research and development ofChinese traditional medicine will provide new ideas for drug-resistant bacteriatreatment by modern science and technology.In this study, we used the microbroth dilution assays and agar plate assays todetermin the MIC(minimum inhibitory concentration) and MBC (minimumbactericidal concentration) of sodium houttuyfonate (SH) inhibits S. aureus ATCC29213and clinical isolates UAMS-1grown in suspension and built the inhibitioncurve; we cultured the S.aureus biofilm on cell cultured plate in vitro; we identifiedand observed the ability of ATCC29213and clinical isolates UAMS-1in biofilmformation by crystal violet and LSCM (laser scanning confocal microscopy). We usedthe agar plate assays to determin the MBIC and MBBC in biofilm; we used the LSCM to observe the different stages of S. aureus ATCC25923biofilm formation treatedwith SH. The results showed that SH had a better actibity against S. aureus insuspension, the MIC and the MBC of SH aganist S. aureus strains (ATCC25923,UAMS-1) were16μg/mL and32μg/mL, respectively. LSCM observed the S. aureusbiofilm cultured in vitro, ATCC25923and UAMS-1were able to form mature biofilmwhich were similar in structure. And, two days biofilm structure were more thick anddense; SH had a low inhibitory activity against mature biofilm of S.aureus strains(ATCC25923, UAMS-1), the MIBC and MBBC were over1024μg/mL; but in theearly stages SH (8μg/mL) can inhibit the biofilm formation.We used zymographic analysis of bacteriolytic hydrolase activities of S. aureusATCC25923cells treated with SH; we prepared the polyclonal antibody against IsdA,the expression of virulence factors and IsdA by ATCC25923treated with SH weredetermined via western blot. The results showed that SH suppressed the activity of S.aureus bacteriolytic hydrolase. And the expression of α-haemolysin, staphylococcalenterotoxin A (SEA), staphylococcal enterotoxin B and IsdA were inhibited bysub-MIC of SH.The study preliminary discussed the molecular mechanism of SH inhibis biofilmin S. aureus, which may provide a theoretic basis for clinical treatment of S.aureusinfections and lay a solid foundation for the science study and clinical application ofSH.