In vitro evaluation of the antibacterial activity of three different central venous catheters against gram-positive bacteria.

The aim of this study was to evaluate the activity of three different catheters against Staphylococcus aureus ATCC 29213 and the slime-producing Staphylococcus epidermidis ATCC 35984 (RP62A). Three central venous catheters were evaluated: one impregnated with silver sulfadiazine-chlorhexidine, one to which minocycline/rifampin is bonded and a novel one into which silver, platinum and carbon are incorporated. A nonantiseptic catheter was used as the control catheter. One-centimeter trisected pieces of catheter were immersed in phosphate-buffered saline (0.01 mol/l) with 0.25% dextrose and incubated. On days 1, 3, 7, 14 and 21, a 1 ml standardized inoculum was added for 30 min and then replaced with phosphate-buffered saline with 0.25% dextrose. One-third of the samples were immediately sonicated and plated to determine bacterial adherence. The remaining segments were incubated for 4 and 24 h to determine the persistence of bacterial adherence. Bacterial adherence to the catheters impregnated with silver sulfadiazine-chlorhexidine was reduced 91-98% for the first 7 days. Adherence of Staphylococcus aureus to catheters into which silver, platinum and carbon are incorporated was reduced 70% on day 1 and 35% on day 3. Adherence to minocycline/rifampin-bonded catheters was quite variable. There was an 85.6-99.8% reduction in the persistence of bacterial adherence to the three catheters compared to controls. Bacteriostatic and bactericidal studies indicated that the effluents from the catheters impregnated with silver sulfadiazine-chlorhexidine were bactericidal, while effluents from the minocycline/rifampin-bonded catheters were bacteriostatic. The antibacterial activity of the effluents from catheters impregnated with silver sulfadiazine-chlorhexidine dissipated by day 7, while the activity of effluents from the minocycline/rifampin-bonded catheters continued to show activity at day 21. No measurable antibacterial activity was detected in the effluents of the catheters into which silver, platinum and carbon are incorporated. These data suggest that catheters coated with antibiotic/antibacterial agents and the novel catheters that incorporate antiseptic agents have different activities against initial bacterial adherence. All of them, however, effectively prevent bacterial colonization by gram-positive bacteria.