BACKGROUND: The formation of bacterial biofilm on the material surface is the core problem of catheter-related urinary tract infection. Many researches have focused on the mechanism and prevention of such category of infection under static or simple hydrodynamic stimulation. The construction of dynamic model of bacterial biofilm of bladder urine flow close to real human diseases is the key to study the pathological mechanism and develop new technology of anti-biofilm infection.
OBJECTIVE: To put forward the concept of turbulent flow shear stress of human bladder urine flow, construct this turbulent shear stress system based on the bacterial biofilm reactor of in vitro bionic human bladder, and explore the formation of E. coli biofilm stimulated by different stresses.
METHODS: An in vitro dynamic bionic bladder urine flow model was designed. E. coli standard strain ATCC25922 was used as research object, and the medical silica gel was used as bacterial biofilm forming carrier. Four artificial urine flow stresses were simulated: hydrostatic pressure, constant turbulent flow shear stress, physiological turbulent flow shear stress and pathological turbulent flow shear stress (simulated urine retention environment). A bacterial biofilm reactor loaded with turbulent flow shear stress was established. Optical density value, colony count, and biofilm surface area of bacterial biofilm suspension were detected 24, 72, 120, and 168 hours.
RESULTS AND CONCLUSION: (1) Optical density value of bacterial membrane suspension: there was significant difference between different urinary stress groups and different test time points (F=110.84, 187.96, all P < 0.000 1), and there was interaction effect between time and stress (F=50.05, P < 0.000 1). From hydrostatic pressure, constant turbulent flow shear stress, physiological turbulent flow shear stress, to pathological turbulent flow shear stress, the number of biofilm bacterial colonies increased. (2) Colony count of biofilm bacterial suspension smear: there was significant difference between different time (F=6.30, P=0.002 9); no difference was found between different urinary stress groups (F=1.11, P=0.400 1); and there was no interaction effect between time and stress (F=0.85, P=0.581 4). However, with the time extension of stress action, the colony count of complex stress group showed an increasing tendency, especially in the pathological turbulent shear stress. (3) Scanning electron microscopic characterization of biofilm bacteria: qualitative comparison between each group and different time points showed that the formation of bacterial biofilm was different from sparse fragments, lumps to large lumps. There were significant differences in the bacterial biofilm surface area between different urinary stress groups and at different times (F=505.72, 1 201.84, all P < 0.000 1), and there was interaction effect between time and stress (F=78.14, P < 0.000 1). From hydrostatic pressure, constant turbulent flow shear stress, physiological turbulent flow shear stress, to pathological turbulent flow shear stress, the biofilm formation increased significantly. (4) The results showed that this turbulent flow shear stress of human bladder urine flow can obviously stimulate E. coli biofilm formation in vitro. Its functional changes and pathogenic mechanism need to be further explored.