Effect Of Luteolin On The Virulence Factors Of Haemophilus Parasuis

Haemophilus parasuis is one of the most prevalent swine diseases in China and even all over the world,resulting in thehuge economic losses to the swine industry.The virulence factors of H.parasuis are extremely complex,the mechanism of virulence as well as the interaction among different virulence factors are currently unclear,which poses a serious threaten to the prevention and control of H.parasuis in pig farm.Hence,a large number of research concentrate on virulence factors of H.parasuis,including outer membrane protein,lipopolysaccharide and neural aminase and so on.In this study,we focus on the effect of luteolin on the expression of H.parasuis? virulence factors in order to provide s new theoretical basis for the prevention and control of the disease in veterinary clinic.According to C linical And Laboratory Standards Institute((CLSI),antimicrobialsusceptibility testing of the Luteolin was performed to test minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC).H.parasuis showed no resistance to luteolin with MIC of 8 ?g/m L and MBC of 16?g/m L.This means that luteolin p lays a effective role in antimicrobial activity to H.parasuiswithout resistance.Real-time PCR amplification and sequencing were used to identified the effect of luteolin on the growth of H.parasuis and the expression of the potential virulence related gene s with different concentration of Luteolin on the effect on the expression of H.parasuis?s 10 related genes.The results showed that luteolin on the relative expression level of virulence genes of standard strain had good inhibitory effect,giving rise to the virulence of H.parasuis declined evidently,which includesouter membrane protein genes(O mp P-5 and Omp P-2),cytolethal distending toxin sub-gene(cdt C),biofilm formation related gene(mvi N),Capsular formation related gene(cap D).But luteolin showed no effect on the others genes,including hemolytic operon genes(hhd A and hhd B),cytolethal distending toxin sub-gene(cdt A),biofilm formation related gene(ga IU),transfer binding protein(tbp A),or even increased the effects to the contrary.This means that the luteolin has different degrees of influence expression of different virulenc genes of H.parasuis.In this study,we demonstrated that luteolin produced antimicrobial activity,especially the virulenc mvi N gene of H.parasuisstrains,which dramatically inhibited the expression of mvi N gene(P<0.01).Luteolin had different degree effects on the expression of 10 related genes of H.parasuis strains.Besides,it showed good inhibition effect on the the virulence genes of H.parasuisstandard strain,which affected the virulence and could be used as candidate virulence inhibitors in H.parasuis further study.