Inhibitory effect of andrographolide on staphylococcus aureus biofilms in vitro

ZHU Si-xia

Abstract：Objective To study the inhibitory effect of andrographolide on staphylococcus aureus biofilms in vitro.Methods 30 clinical isolates of staphylococcus aureus were collected and screened for biofilm positive strains by Congo red plate method .Semi-quantitative testing was done to measure the biofilm by using crystal violet staining .The MIC and SMIC of antibiotics were determined by double dilution of the microbroth with vancomycin as the positive control . XTT reduction assay was used to evaluate the influences of andrographolide on initial adhesion capability of staphylococcus aureus biofilm .Results Of 30 strains of staphylococcus aureus , there were 12 biofilm positive strains that accounted for 40%detected by Congo red plate , while 22 strains (73.3%) were positive for semi quantitative biofilm test by crystal vi-olet staining.SMIC50 and SMIC80 of andrographolide against staphylococcus aureus biofilms were 125 and 500 mg/L, re-spectively.Andrographolide significantly inhibited the early adhesion of staphylococcus aureus biofilm at 1000, 500 and 250 mg/L.Conclusion A certain concentration of andrographolide can inhibit staphylococcus aureus biofilm formation and adhesion , but the effect is less than that of vancomycin .