A longitudinal in vitro antimicrobial evaluation of two silver polymer surface treatments for peritoneal dialysis...

The oligodynamic effect of silver has been utilized in medicine for many decades. This study evaluated the antimicrobial properties of two silver polymer surface treatments over 9 months to assess their usefulness for chronic percutaneous access. Silicone catheters were either dip-coated with micronized silver oxide in a silicone matrix (AgX) or impregnated with silver using an ion beam deposition process (Spire Argent I). Four-inch (10-cm) segments were shaken continuously in 10 mL minimum essential media (MEM) with 2% fetal bovine serum (FBS) at 25 degrees C. The medium was replaced weekly. Monthly eluate samples were assayed for Ag+ concentration using ICP atomic emission spectroscopy. Bimonthly, segments were removed, placed in fresh medium inoculate with 10(5) colony-forming units (cfu)/mL Staphylococcus aureus ATCC 25923 and quantitated over 24 hours for bacterial survival/growth. Relative to control catheters, there was a mean log10 reduction of S. aureus of 4.4 with AgX and 1.7 with Spire Argent I persisting over the 9-month study period. Silver ion elution followed a biphasic pattern with both coatings establishing a steady state of 0.2 ppm at 4 months. These data suggest that the test surface coatings employed will deliver long-term oligodynamic activity when implanted percutaneously.