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

: 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.