Construction Of A Turbulent Shear Stress System For Human Bladder Based On A Bacterial Biofilm Reactor

Objective:The unreasonable using and abusing of antibiotics in clinical practice have led to the great increasing of drug resistance of bacteria and the emergency of "super" multi-drug resistant bacteria,which brought great difficulties to anti-infection treatments.Catheters are widely used in clinical scenarios,among which the catheter-associated urinary tract infection(CAUTI)are the most common worldwide,second only to respiratory infections.The incidence of urinary tract infection in nosocomial infection accounts for about 40%,and the urinary tract infections in most of these patients are closely related to indwelling catheters.According to the statistics,the longer the time of indwelling catheter is,the patients will inevitably have bacteriuria,but with or without clinical symptoms.CAUTI are serious challenges for clinicians and patients,and anti-infective therapies often fail because we consider them as anti-bacterial rather than anti-biofilm infections.The study found that patients with urinary tract infections were coated with an amorphous complex(bacterial biofilm)in the wall of their urinary tract,which is the pathogenic factor of catheter-associated infections.Currently,there were many reports on the research of bacterial biofilms,most of which were based on biology and chemistry,such as physical and chemical properties of biofilms,research devices,drug resistance mechanisms,etc,but there were only few studies on the differential expression of biofilms in terms of the shear stress of human urine flow.In this experiment,we put forward a turbulent shear stress concept of human urine flow pattern for the first time,intend to explore the generation and differential expression of bacterial biofilm in bionic biofilm reactor with human bladder bacteria stimulated by hydrostatic pressure,constant current shear stress,physiological shear stress and pathological shear stress from the perspective of mechanics.Methods:Based on the principles of fluid mechanics and knowledge of mechanical biology,we construct a turbulent shear stress model of human bladder in vitro with independent intellectual property rights,simulate the human bladder urine flow under hydrostatic pressure,constant current shear stress,physiological shear stress and pathological shear stress(controlled by peristaltic pump and stirring rod),the escherichia coli was used as the experimental model bacteria,and the medical gel silica membrane(instead of the catheter)was used as the carrier of bacterial biofilm,simulate the stimulation of escherichia coli under different shear stress.The differences in biofilm generation were analyzed by counting bacterial colonies,optical density of bacterial suspension(OD value is absorbance value),characterization by CLSM,and characterization by SEM.Results:A turbulent shear stress loading system for a bacterial biofilm reactor simulated the human bladder was successfully constructed.Through biofilm colony count,OD value measurement and CLSM combined with SEM bacterial biofilm characterization,it was confirmed that with the extension of stress duration and the increase of stress application,the generation of bacterial biofilm increased significantly,and the difference between groups was significant,the good film forming performance of the reactor was verified,and it was suggested that the turbulent shear stress of urine flow might play a important role in the initial infection of biofilm.Conclusion:Although the diagnosis and treatment of CAUTI have received extensive attention and research,the mechanism of infection and drug resistance is still unclear,so the infection is difficult to treat,easy to increase the patient's pain and psychological stress,increase the patient's economic burden,and even increase the fatality rate.Most studies have confirmed that bacterial biofilm is the pathogenic factor of CAUTI.The formation of bacterial biofilms can attach to inert or living organisms,which is a reticular polymer complex,and can grow in a static or dynamic environment,the complexity and robustness of its structure make it difficult to infiltrate antimicrobial agents,which cannot eradicate the biofilm,but tend to increase bacterial resistance and bacterial variability.The particularity of urine-associated infections lies in the difference in the fluid dynamics of the bladder,and this hydrodynamics led to the early adhesion of bacterial biofilms,In this study,for the first time,it was proposed that the urine flow in the bladder indwelling catheter formed a unique unsteady flow stress environment,that is turbulent shear stress,and preliminarily confirmed the role of turbulent shear stress in the infection of biomaterials.