Establishment And Application Of A Model Of Staphylococcus Aureus PJI With A New Luminescent Clinical Strain

Prosthetic joint infection（PJI）is a catastrophic postoperative complication and Staphylococcus spp.are the predominant pathogens responsible,particularly Staphylococcus aureus（S.aureus）.On the pathogenesis in vivo,prevention and treatment strategies of PJI,although lots of in vitro studies have been conducted,the significant differences in these in vitro results are not enough to clarify the real PJI pathogenesis in vivo,also cannot provide the effectiveness of various interventions in vivo.The researches on PJI mechanism in vivo depends on the clinically relevant tool bacteria,infection markers could be monitored in real-time and reasonable and effective animal models.BLI combined with bioluminescent bacteria can not only real-time quantitative monitor the infection in vivo,but also provide lots of true and reliable informations on it,with reducing the consumption of experimental animals.In this study,after screened PJI clinical strains,a S.aureus clinical strains ST1792isolated from PJI patients was obtained.The Lux gene was transferred to ST1792 by phage transduction,and then obtained the stable luminescent S.aureus clinical strains ST1792-lux.20 BABL/c mice were used as model animals.Kirschner wires and titanium tablets were used as left knee prosthesises and back subcutaneous prosthesises,respectively.During operation,ST1792-Lux（10⁵ CFU）was inoculated into the cavity of the left knee or subcutaneous.Finally,we successfully established an animal model of PJI or prosthesis-associated soft tissue infection with stable luminescent S.aureus clinical strains.In order to further explore the mechanism of PJI and its effective prevention and control measures in vivo,an innovative nano-MgF₂ films were deposited on titanium substrate via magnetron sputtering.Using the above animal model,the antibacterial behavior and mechanism of nano-MgF₂ films were systematically investigated in vitro and in vivo.It was found that,both the traditional SD rat osteomyelitis model and the novel stably luminescent mouse infection model demonstrated that nano-MgF₂ films exerted superior anti-infection effect in vivo,however,the nano-MgF₂ films only possessed excellent anti-biofilm ability in vitro.Further,the complementary investigation of blood-MgF₂-bacteria co-culturing revealed that the nano-MgF₂ films improved the antibacterial ability of PMNs through enhancing their phagocytosis and stability.Based on the research results,a plausible mechanism was put forward for the predominant antibacterial effect of nano-MgF₂ in vivo,which may originate from the dual antibacterial properties,direct anti-biofilm effects and indirect immune enhancement activities of nano-MgF₂ films,which also emphasizes the potential clinical use in orthopedics.Based on the clinical problem,through the clinical screening,gene construction and so on,we successfully established the stable luminescent S.aureus clinical strains tool bacteria and related animal models.Using this platform,to our knowledge,it was the first time to explore the antimicrobial behavior and mechanism of innovative nano-MgF₂ films from the perspective of innate immunity both in vitro and in vivo.In summary,this study may establish a research platform for orthopedic prosthesis-associated infection in vivo and in vitro and pave the way towards the clinical applications of innovative nano-MgF₂ films.