Rutin Inhibits The Formation Of S.suis Biofilm And Its Effects On The Expression Of Cps Gene Cluster And Virulence Genes

Biofilms are microbial sessile communities characterized by cells that are attached to a substratum or interface or to each other,are embedded in a self-produced matrix of extracellular polymeric substances and exhibit an altered phenotype compared to planktonic cells.Biofilm cells are known to be 10~1,000 fold more resistant to antimicrobial agents than planktonic cells.Streptococcus suis(S.suis)is a major zoonotic microorganism that causes severe diseases in humans and pigs.Biofilm of S.suis is difficult to treat and could cause persistent infection.Therefore,how to inhibit BF production has become a veterinary clinical problem to be solved.Capsular polysaccharide is a virulence factor of S.suis 2.Its synthesis is regulated by the cps gene cluster.It can affect the formation of S.suis biofilm by mediating adhesion.The mutation and expression of the cps gene cluster can affect synthesis of capsular polysaccharide to promote bacterial adhesion and biofilm formation.Rutin is a kind of flavonoids,which is widely existed in nature.It was discovered to inhibit biofilm formation of S.suis via analyzing the relationship between the spectrum and the impact of Syringa oblata Lindl.aqueous extract on S.suis biofilms in vitro in our laboratory.However,how does rutin affect S.suis biofilms at the molecular level is unclear.In this study,the effects of rutin on the biofilm of S.suis were observed by the crystal violet staining and scanning electron microscopy in vitro.The effects of rutin on the gene expression of the cps gene cluster and virulence gene were investigated at the adhesion stage of biofilm formation of S.suis.Firstly,the effect of rutin on cps gene cluster was studied from the level of gene mutation and m RNA expression.Then the Real time-PCR is applied to detect the 1/4 MIC of rutin on m RNA expression of virulence genes ef,fhb,fbps,gdh,mrp,sly and Lux S.The result showed that the MIC of rutin against S.suis is 0.3125 mg/mL.This study demonstrates that rutin at the 1/2 MIC and 1/4 MIC can effectively inhibit S.suis biofilm formation.The growth of S.suis doesn't change under 1/4 MIC rutin by depicting the growth rate of S.suis,but the adhesion of S.suis is inhibited.Our results indicated that 1/4 MIC rutin compared with controls can upregulate the m RNA expression level of cps2 D,cps2E,cps2 Q,cps2S,cps2 J,cps2C,cps2 R,gdh and mrp.On the other hand,it could decrease the m RNA expression level of cps2 M,cps2V,cps2 U,cps2B,cps2 K,ef and sly.In conclusion,rutin can inhibit the formation of S.suis biofilm by regulating the synthesis of capsular polysaccharide and virulence genes of S.suis.Rutin can be used as a good adhesion inhibitor.