| Staphylococcus aureus (S. aureus) is one of the most common food-bornebacteria. Its harmfulness has always been the concern of the world food securityorganization. S. aureus can be attached to the surface of human organs or food. It canproduce polysaccharide substance, protein, the sediment of inorganic salt and organicsalt sediment and other material. The bacterial will be wrapped by these substances tobiofilm. After the biofilm formation, the ability to the bacterial resistance of hostimmune system and inhibitors will greatly improve. The world health organization(WHO) has announced, that foodborne diseases and food contamination has become aworldwide public health problem. Billions of foodborne disease cases has beenhappened every year. At least a third of the population suffer from foodborne diseaseseach year in developed countries. It makes more difficult in the treatment ofstaphylococcus aureus, with the emergence of methicillin-resistant staphylococcusaureus. Therefore, the way to find effective drug resistance of S aureus biofilm hasbecome an urgent task. The research of staphylococcus aureus inhibitors has beengoing on. They hope to find a new type of inhibitor with low concentration characterstable, highly effective, non-toxic and lower cost. In the nature of natural products andherbal plants contains many small molecule compounds with antibacterial structure.These provide us more abundant resources to search for the new type of S aureusbiofilm inhibitor.This study discusses the inhibition mechanism of planktonic S aureus and biofilm.The ability of S aureus biofilm formation has been identified by Congo red, crystalviolet semi-quantitative method, disk diffusion Test and confocal laser scanningmicroscope(CLSM). Minimum bacteriostatic concentration (MICs), Minimumbactericidal concentration (MBCs), minimum bacteriostatic concentration (MIBCs)and minimum bactericidal concentration (MBBCs) has been tested by double dilutionmethod. The result shows that MICs is in the range of8to16μg/mL; MBCs is inrange of8to32μg/mL; MIBCs is in the range of32to128μg/mL and MBBCs is over512μg/mL. It can be seen that honokiol has significant bacteriostatic action tostandard strains and food isolates. The growth curve of planktonic S aureus andbiofilm has been studied by spectrophotometer. This proves the inhibition effect ofhonokiol.In this study, we discuss the bacteriostatic mechanisms of honokiol through therelease of extracellular DNA (eDNA), the secretion of Polysaecharide imercellularadhesion (PIA) and the expression of genes. The results show that the release ofeDNA, the secretion of PIA and the expression of genes have reduced(P>0.05). Inaddition, we also discuss the expression of the virulence proteins and their genes byRT-PCR and Western Blot. The results show that the honokiol could obviously inhibitthe expression of alpha hemolysin, SEA, and SEB.In the study, we also studied the scavenging effect of planktonic S.aureus andbiofilm attached to the stainless steel sheet. Experimental results show that when theconcentration of honokiol is16μg/mL, the infection of S.aureus in milk sterilizationrate has reached more than99%. The sterilization rate to the biofilm attached to thestainless steel sheet is above99%.This study clarified the molecular mechanisms of planktonic S.aureus and biofilmInhibited of honokiol. It has provides a new type of antibacterial agent for theanti-corrosion, preservation, extending the shelf life. In the meantime, it provides anew treatment options of the clinical treatment of S.aureus bacteria infection. |
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