An assessment of the ability of a silver-releasing device to prevent bacterial contamination of urethral catheter drainage systems

Objective To investigate the ability of a silver-releasing device to protect the catheterized bladder from infection by blocking the ascending migration of bacteria from contaminated urine-drainage bags. Materials and methods A simple physical model of the catheterized bladder and drainage system was used with the device located in the drainage-tube just below the sampling port. Urine was supplied to the model at 1.0 mL/min and the drainage bag was contaminated with Pseudomonas aeruginosa, Escherichia coli and Proteus mirabilis. Over 10 days, urine from the bag, catheter sampling-port and bladder were examined for contamination. Results Bacteriological analysis showed that the mean time for test organisms to reach the sampling ports of four different control bag systems ranged from 5.7 to 7.7 days. Urine from the sampling ports of the test systems incorporating the silver device remained sterile for 10 days. The device also prevented the growth of the large populations of bacteria (10(8) colony-forming units per mi,) that occurred in the control bags. While scanning electron microscopy showed the formation of bacterial biofilm throughout the control drainage systems, no bacterial colonization was visible on the surfaces of the test systems. Chemical analysis established that the devices consistently generated concentrations of silver in urine ranging from 1.0 to 2.0 mu g/mL. Conclusion The incorporation of the silver-releasing device into the drainage systems produced an antibacterial barrier which protected the catheterized bladder from intraluminal contamination for at least 10 days. These in vitro tests suggest a useful role for the device in controlling infection in patients undergoing short-term indwelling bladder catheterization.