| Staphylococcus aureus(S.aureus)is a common pathogen that infected human and animal and threated health of human and amimal serously.In order to complete its necessary life cycle,S.aureus has developed powerful ability to adapt to different environments.For example,methicillin-resistant S.aureus(MRSA)appeared in recent years,which is high resistant to common antibiotics and increases the difficulty of prevention and treatment for S.aureus infection.More worse,its ability to resist against antibiotics keeps growing strong,considered that it had been isolated clinically that a strain of MRSA(hVISA)had reduced sensibility to vancomycin that is the most effective drugs in treatment of S.aureus infection.S.aureus have high adaptability and pathogenicity,due to its mechanism of immune escape.The virulence factor is the molecular basis of its immune escape.Therefore,Studying the virulence factors of S.aureus is meaningful for the exploration for how to prevent and treat S.aureus infection.O-acetyltransferase A(OatA)is a important virulence factor of S.aureus,which makes S.aureus highly resistant against lysozyme and increases the viability of S.aureus.However,immunomodulatory mechanism of OatA in S.aureus infection remain to be unclear.Therefore,we initially constructed S.aureus USA300 oatA gene deletion strain and oatA gene complemented strain,and detected the resistance of S.aureus against lysozyme though lysozyme plate diffusion assay,providing important experimental material for the study of OatA.Innate immunity plays a key role on the defense against pathogens invasion.Therefore,we explore the role of OatA on innate immunomodulatory by utilizing S.aureus to infect macrophage.In vitro we found that S.aureus-induced cell death was an early events and cell didn't die any more in the late infection.During the early time of infection,the level of oat A gence transcription gradually decreased.During the later period,oatA increased from the lowest point.These results indicated that there exists the relation between OatA and cell death.Subsequently,we utilizd oatA deletion to simulate the situation that oatA is at low level of expression.As the results showed,oatA deletion obviously increased cell death,indicated that there really existsthe relation between Oat A and cell death.Furthermore,we discoverd that cell death induced by oatA deletion was dependent on lysozyme,and oat A deletion increased bacteriolysis in the macrophage.These indicate that S.aureus control bacteriolysis by OatA in order to control macrophage death.We further analyzed the effect of cell death.The result showed that cell death resulted in a large number of bacteria released into the outside of cell.Furthermore,the type of cell death is involed in pyroptosis and necroptosis dependent on AIM2,but independent NLRP3.In order to explore the related mechanism in vivo during S.aureus infection.we firstly constructed skin infection with S.aureus.As the results showed,OatA deletion obviously strengthens S.aureus infection,Furthermore,this effect was dependent on AIM2.Systemic infection is also a type of S.aureus infection.Therefore,we further constructed mouse systemic infection throuth intravenous injection with S.aureus to analyze the the role of OatA.As the results showed,oat A deletion significantly strengthened toxicity of S.aureus,increased bacterial burden and KC,CCL2,IL-6and IL-1? secretion in kidney.Further study showed that AIM2 deficiency inhibited the mortality of mice,and bacterial burden and KC,CCL2,IL-6 and IL-1? secretion in kidney infected with oat A deletion muant,indicated that AIM2 plays a role in the systemic infection with oatA deletion mutant.Considered in vitro,we conclude that during S.aureus infection,OatA virulence deletion increase inflammasome activation and necroptosis dependent on AIM2,cell death induced by Oat A virulence deletion is related to bacteriolysis and benefit bacterial dissemination and colonization,and oatA deletion enhances the pathogenicity of S.aureus,dependent on AIM2 signal. |
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