Efficacy of silver-coating central venous catheters in reducing bacterial colonization

Objective: To compare silver-coated and uncoated central venous catheters r egarding bacterial colonization, To assess the relative contribution of cat heter hub and skin colonization to catheter tip colonization. Design: Prospective, randomized clinical trial, Setting: Intensive care unit in a university hospital. Patients: Patients after cardiac surgery who required a central venous doub le lumen catheter (DLC), interventions: Sixty-seven adult patients were prospectively randomized to receive either a silver coated (S group, n = 34) or an uncoated control (C group, n = 33) DLC. Blood cultures were drawn at catheter removal, and remo ved catheters were analyzed with quantitative cultures. Typing of microorga nisms included DNA fingerprinting, Measurements and Main Results: Catheters were removed if no longer necessar y and aseptically divided into three segments: segment A, the catheter tip; segment B, an intermediate section; and segment C, the subcutaneous portio n, Bacterial catheter colonization was quantitatively measured using sonica tion to detach adherent bacteria from the catheter segments in the broth an d subsequent culture of an aliquot, Selected isolates of coagulase-negative staphylococci and other bacteria from catheter segments were examined by m eans of pulsed field gel electrophoresis (PFGE) after macrorestriction dige stion of bacterial DNA to study colonization pathogenesis, Quantitatively lower bacterial colonization could be demonstrated on the si lver coated catheters (200 +/- 550 colony forming units [CFUs]/cm catheter segment; mean +/- so). The difference in the control catheters (1120 +/- 53 50 CFUs/cm catheter segment; mean +/- so) was not, however, significant (p = .25), The frequency of colonization of at least one catheter segment was 52.9% fo r the silver-coated catheters and 57.6% for the control catheters (p= .44), without any significant differences in the colonization of corresponding c atheter segments, The rate of significant catheter colonization (i.e., greater than or equal to 10(3) CFUs/cm catheter by quantitative catheter culture or greater than or equal to 10(3) CFUs/mL by luminal flush) was nine in the silver group an d seven in the control group, a difference that failed to reach significanc e (p = .41), Two patients in both groups developed catheter-related bactere mia, Pattern analysis after PFGE demonstrated that about 70% of the isolates fou nd on the catheter tip were identical with those on the skin at the inserti on site, whereas about 75% were identical with those recovered from the hub . In 29% of colonized catheters, identical bacteria were found on the hub a nd the skin at the insertion site. Conclusions: Silver coating of DLCs did not significantly re duce bacterial catheter colonization compared with the control catheters. PFGE analysis o f coagulase negative staphylococci and other bacteria demonstrated various pathogenic routes of catheter related colonization, whereby the microorgani sms of the skin flora around the insertion site must be regarded as the mai n source of catheter-related infections.