The purpose of this study was to evaluate the ability of vascular
polyester grafts with antibacterial properties to resist colonization following surface contamination by methicillin-resistant Staphylococcus aureus (MRSA) in an experimental canine model or aortic graft
infection. Twenty-four pathogen-free dogs underwent replacement of the infrarenal aorta with either a
rifampin-soaked (30 mg/mL) or
silver-impregnated (Ag-
acetate) woven
polyester graft. Following implantation, the external graft surface was inoculated with 2 mL of 10(7) colony-forming units/mL (CFU) of MRSA. Preoperative
antibiotic prophylaxis consisted of a single intravenous dose of 500 mg of
sodium cefazolin. Four grafts of each type were explanted at 3, 7, and 14 days after implantation. Quantitative cultures (CFU/specimen) of perigraft fluid (1 mL), graft material (1 cm segment), and adjacent aorta (1 cm segment) were performed. Differences between grafts are expressed as % mean log reduction in recoverable CFU compared to the inoculation
solution concentration of 10(7) CFUs. At 3 days, explanted
rifampin-soaked grafts exhibited no MRSA growth (4 of 4 grafts) and a > or =97% mean log reduction of MRSA CFUs from the adjacent aorta and perigraft fluid (
PGF). At 3 days, all
silver-bonded grafts exhibited signs of
infection and a mean log CFU reduction of MRSA ranging from 68% (absolute range 10(1)-10(3) recoverable CFU) for the graft, 79% (absolute range 10(1)-10(3) recoverable CFU) for the aorta, and 86% (absolute range 10(1)-10(4) recoverable CFU) for
PGF. The 7-day
rifampin group had an average log reduction in MRSA CFU of 72% (graft), 58% (
PGF), 75% (aorta). Quantitative cultures of 14-day
rifampin grafted demonstrated continued bacterial growth suppression with mean MRSA CFU log reductions of 82%, graft; 72%,
PGF; 89%, aorta.
Silver-bonded grafts demonstrated <50% mean CFU reduction in MRSA growth at 7 days (absolute range 10(5)-10(7) recoverable CFU) and 14 days (absolute range 10(3)-10(7) recoverable CFU). No animal died from
sepsis or anastomotic
hemorrhage. Neither
rifampin- nor
silver-bonded grafts demonstrated prolonged resistance to surface MRSA contamination.
Rifampin-soaked
polyester grafts exhibited a marked but transient resistance MRSA colonization likely the result of high
antibiotic concentration in the perigraft tissue. While both types of grafts failed to eradicate the MRSA
infection future research with
silver-bonded grafts that have an additional
antibiotic attached may have a place in the treatment of MRSA
infection.