Abstract: The effect of Rabdosia rubescens extract on biofilm formation of Staphylococcus aureus was tested.Inhibitory activity of R.rubescens extract with different concentrations and different addition times on the biofilm formation of S.aureus were analyzed by crystal violet staining assay and sliver staining methods.The results showed that the MIC and MBC of R.rubescens crude extract against S.aureus were 125 μg/mL and 250 μg/mL,respectively.Under sub-MIC concentrations,the intervention effect of R.rubescens extract on biofilm formation of S.aureus was not obvious,but when the concentration of R.rubescens crude extracts was more than double MIC,it can significantly inhibit the biofilm formation of S.aureus and the best inhibition effect can be achieved after adding drugs at the initial time of biofilm formation.The inhibition rate was over 79% when the concentrations of R.rubescens crude extracts were 2MIC.The inhibition rate was only 60% at 24 h of biofilm formation after adding drugs.The eradication effect on biofilm and the inhibition of extracellular polysaccharide(EPS) synthesis were studied by using crystal violet staining assay and sliver staining methods.The results also showed that the eradication effect of R.rubescens crude extracts on biofilm and the inhibition of its on extracellular polysaccharide synthesis were weak.An obvious decrease of S.aureus biofilms and EPS were observed after adding drugs at the initial time of biofilm formation when the concentration of R.rubescens crude extracts was more than double MIC.This study provided a theoretical basis for the wide application of R.rubescens extract in food storage and preservation,as well as antibiotic-free feed.

Key words: Rabdosia rubescens, Staphylococcus aureus;biofilm;antibacterial activity