The Mechanism Of Hemodialysis Catheter-related Infections

Hemodialysis can bring end-stage renal disease patients with the hope. And the establishment of vascular access is the prerequisite for patient maintenance hemodialysis. Deep venous catheter can be quickly established, less injury and the advantages of effective dialysis used widely in clinical. However, with the catheter indwelling time, the corresponding complications increasing, including catheter-related infection which is one of the most serious complications. Catheter-related infections often lead to catheter removal, even more to be the major cause of death.Once deep venous catheter-related infections occurred in hemodialysis, it's difficult to achieve therapeutic effects even if the systemic treatment of anti-infective by use of sensitive antibiotic. It reported the treatment of deep vein indwelling catheter-related infections in hemodialysis by closing catheter tubes with antibiotics and heparin; however, heparin and antibiotic was incompatible and ineffective. In 2002, we assume that the deep venous catheter implanted in the hemodialysis patient's body, in accordance with the principle of fluid mechanics, the blood flow velocity in the center of duct wall is fast, but which near the duct wall is relatively slow where plasma protein maybe can adsorption and stranded in and formed a layer of plasma protein biofilm; the deep venous catheter need switch many times, bacterial can invasion and implanted within the plasma protein biofilm in catheter wall. In the course of each dialysis, blood flows through the catheter, the bacteria and toxins released into the blood from the biofilm which resulted in chills, high fever, elevated blood poisoning and other systemic symptoms. Therefore, we envisaged that closed the catheter tubes with urokinase and antibiotic, urokinase maybe dissolved the plasma proteins biofilm and made bacteria exposed which combined antibiotics killed bacteria to achieve the purpose of the elimination. Thanks to our many years of clinical exploration, the closure of urokinase combined with antibiotics in 3-5 cycles, achieved very satisfied results. The article aim atconfirm its mechanism through in vitro methods.ObjectiveThe establishment of plasma protein biofilm and bacterial implanted plasma protein biofilm model in vitro confirmed deep venous catheter-related infections mechanism. The intervention with different concentrations of urokinase and urokinase combined with antibiotics and different concentrations of heparin and heparin combined with antibiotics on bacterial implanted plasma protein biofilm to study its mechanism.Methods1. Deep vein hemodialysis catheter, vertical incision, collecting the part of interval, cutting edge, then cutting into small rectangular with the size of 2mmx3mm and an area of 6mm .2. Hemodialysis patients plasma 3.5ml, divided into 7 copies in average, each adding a small catheter, culture in 37.2 degree temperature box, every 12h shaken once and each with 5min; every 24h take one small catheter and observe under confocal microscope or and scanning electron microscopy, the establishment of the plasma proteins biofilm model in the inner wall of the catheter after 7 days.3. Collection coagulase-negative staphylococci strains, do antibiotic sensitivity test get sensitive antibiotic of amikacin; semi-solid culture method used to preserve bacteria; blood agar plate culture to form colonies; the preparation of sterile saline and bacterial colonies to get a concentration of 0.5×10~6 bacterial suspension.4. Establish the plasma protein biofilm model in accordance with the above-mentioned method, then adding into the culture medium with a concentration of 0.5×10~6 coagulase-negative staphylococci bacteria, every 12h shake once and change half culture medium one day, every 24h take out one small catheter and observe under confocal microscope, the establishment of bacterial implanted plasma proteins biofilm model in the inner wall of the catheter after 7 days.5. Divided bacterial implanted plasma proteins biofilm model into 4 groups to intervene, normal saline group, antibiotic group, urokinase and urokinase combined with antibiotic group, heparin and heparin combined with antibiotic group observe under confocal microscope and countbacteria within the implanted plasma protein biofilms.Results1. The formation of plasma protein biofilm in the inner wall of thecatheter after 7 days culture with Hemodialysis patient's plasma.2. You can see the bacterial implanted plasma protein biofilm formed in the inner wall of the catheter after 7 days culture with Hemodialysis patient's plasma, and then joined the bacilli continue to train 7 days.3. The strain sensitive to amikacin.4. The intervention of different concentrations of urokinase and it jointed with amikacin to bacterial implanted protein biofilm, with the the concentration of urokinase increased its role was obvious; the intervention of different concentrations of heparin and it jointed with amikacin on bacterial implanted protein biofilm was poor; with theconcentration of heparin increase it role of damage was not obvious.Conclusion1. The successful establishment of plasma proteins biofilm model andbacterial implanted plasma protein biofilm model in the inner wall of the venous catheter.2. Urokinase can dissolve bacterial implanted plasma protein biofilm,make bacteria exposed and easy be killed by antibiotic.