Is Oxidative Stress Important in AAA Pathogenesis

Objectives: Graft infection often involves several different organisms. Antibiotic-impregnated polymethylmethacrylate (PMMA) beads may be effective in controlling reinfection after infected graft replacement. We sought to determine an effective antibiotic combination in PMMA beads for use in vascular graft infection. Methods: PMMA beads were impregnated with different combinations of antibiotics including daptomycin (DA), tobramycin (TO), and meropenim (ME). Beads were plated into separate 0.8% Mueller-Hinton agar plates with vancomycin-resistent enterococcus (VRE), Klebsiella, S. epidermidis, and methicillin-resistent Staphylococcus aureus (MRSA). Antibiotic inhibition was recorded in millimeters using the disc agar-diffusion method and averaged from three separate platings. Results: DA alone was not active against Klebsiella (average 1⁄4 0 mm). TO alone was not active against VRE, Klebsiella, or MRSA. ME showed broad-spectrum activity against all organisms with >15 mm inhibition halo. The efficacy of ME was decreased by TO but not DA. Adding DA and TO to ME did not improve efficacy. Conclusions: Meropenem in PMMA beads shows activity against difficult pathogens encountered in vascular graft infections. Daptomycin can be added for doublecoverage against multi-drug resistant gram-positive pathogens such as VRE and MRSA. Tobramycin appears to reduce the efficacy of meropenem when used in combination.