| Streptococcus suis is an important pathogen causing a variety of life-threatening infections that include meningitis, septicemia, endocarditis, arthritis and pheumonia in pigs. Streptococcus suis is devided into35different serotypes(1-34,1/2) according to polysaccharidic capsule, among which, S.suis serotype2is known to be the most virulent and frequently isolated serotype. At present, S.suis is found to form biofilm in vitro and in vivo by researchers around the world, BF is vital for the survival of bacteria which is affected by various factors. Quorum sensing system plays an important role in the pathogenic biofilm formation. Autoinducer2(AI-2)is a universal quorum sensing(QS)molecule that mediates intergeneric signalling in multispecies bacterial communities to communication used to coordinate bacterial activities. LuxS/AI-2not only influences the formation of BF, but also bacterial virulence factors. Intervened with S.suis QS system may become the potential to the future development strategy of antimicrobial drugs.We investigated the efficacy of aqueous extracts of Rhizoma coptidis, berberine hydrochloride, palmatine chloride and jatrorrhizine chloride in preventing S.suis biofilm formation by means of in vitro model of BF, crystal violet assay, plate count assay and SEM. Results showed that sub-minimal inhibitory concentrations of berberine hydrochloride blocked the formation of S.suis biofilm(P<0.01) and aqueous extracts of Rhizoma coptidis, palmatine chloride at sub-minimal inhibitory concentration could decrese biofilm formation(P<0.05).Real-time PCR was employed to detect the sub-inhibitory concentration of Rhizoma coptidis and its monomers on mRNA expression by the density of sensing system signal molecules LuxS/AI-2protease and virulence gene cps, sly, gapdh, gdh, ef, mrp, fbps in S.suis biofilm.. Significantly decreased in LuxS/AI-2protease was observed of aqueous extracts of Rhizoma coptidis, berberine hydrochloride, palmatine chloride and jatrorrhizine chloride compared with biofilm control to2.44,4.35,4.00and1.41times(P<0.05). Compared with biofilm controls, aqueous extracts of Rhizoma coptidis group sly, gapdh, fbps gene decreased4.35,1.54and1.75times(P<0.05),cps,gdh,mrp increased1.79,1.72and1.28times(P<0.05); berberine hydrochloride group,mRNA expression of sly, gapdh, ef gene decreased3.13,3.85and2.33times (P<0.05),cps, gdh, mrp gene increased1.54,1.55and1.71times(P<0.05); palmatine chloride group gapdh, ef, fbps gene decreased1.89,2.13and1.89times(P<0.05),cps, gdh gene increased1.53and2.15times (P<0.05); jatrorrhizine chloride group ef, gapdh gene decreased1.82and1.92(P<0.05), cps, mrp, gdh gene increased1.69,1.18and1.87times(P<0.05). Results show that aqueous extracts of Rhizoma coptidis and its monomers could regulate virulence genes in S.suis biofilm.In conclusion, aqueous extracts of Rhizoma coptidis and its monomers could intervene with S.suis biofilm formation, plays an important role in regulation of luxS protease and S.suis virulence genes. |
