The Study On The Molecular Mechanism Of Inhibitory Effect Of Aloe-emodin On Staphylococcus Aureus Biofilm

Staphylococcus aureus(S.aureus)is one of main pathogens causing infection of tissues and organs of human and animals.This pathogen encodes a large number of virulence factors and causes a variety of diseases.The characteristics of S.aureus are rapid transmission,strong pathogenicity,multi drug resistance and the others,posing a challenge to clinical treatment.S.aureus has the ability to form biofilms.The formation of biofilm can reduce the level of bacterial cell metabolism,producing barriers that enhance their sensitivity to antibiotics and damage the host defense system.Due to bacterial resistance and antibiotic adverse reactions,the development of effective drugs from chemical compounds tends to be increasingly difficult.Therefore,resources of traditional Chinese medicine provide a broad space for the development of new antibacterial drugs.In this study,we established biofilm model of S.aureus ATCC29213 strain in vitro.The results showed that S.aureus ATCC29213 had the strongest ability to form biofilm in a Brain Heart Infusion(BHI)Medium containing 3% NaCl and 0.5% glucose.We screened the phytochemicals with antibiofilm activity against S.aureus ATCC29213 from different traditional Chinese medicine monomer compounds on 96-well polystyrene plates by crystal violet staining assay.The results showed that aloe-emodin at 256?g/mL markedly inhibited S.aureus ATCC29213 biofilm formation,and the minimum inhibitory concentration(MICs)of aloe-emodin against S.aureus ATCC29213 were more than 1024?g/mL(MICs > 1024 ?g/mL).The effect of aloe-emodin on S.aureus ATCC29213 biofilm was further verified by crystal violet staining and fluorescence microscopy.The results showed that aloe-emodin dose-dependently inhibited S.aureus ATCC29213 biofilm formation and inhibits biofilm formation on abiological surfaces.To study the effect of aloe-emodin antibiofilm activity,aloe-emodin was added to the cultures of S.aureus ATCC29213 at different times points during the development stage of the biofilm.These results showed that aloe-emodin would mainly affected the initial adhesion stage and the proliferation phase.Enzymatic hydrolysis experiment indicates that protein was the main component of the S.aureus ATCC29213 biofilm extracellular matrix.The effect of aloe-emodin on the extracellular matrix of biofilm was studied by confocal experiments,autolysis experiments and congo red experiments.The results showed that aloe-emodin had an inhibitory effect on extracellular protein and extracellular polysaccharide instead of extracellular DNA(eDNA).In summary,this study preliminarily demonstrated the molecular mechanism of the inhibitory effect of aloe-emodin on S.aureus biofilm.Aloe-emodin is expected to become the lead compound of S.aureus biofilm targeting medicine and provide a theoretical basis for the subsequent design of new drugs research.