Elution of vancomycin and tobramycin bonded to vascular grafts

The elution of vancomycin and tobramycin from vascular grafts sealed with collagen and human blood was studied in vitro. The release of antibiotics was measured in three different types of soaked grafts, including grafts soaked with antibiotic after being sealed with albumin, those sealed with antibiotic and albumin mixture and those impregnated with fresh blood and antibiotic mixture. Each antibiotic was tested at two different concentrations, i.e. 5 mg/ml and 10 mg/ml for vancomycin and 2 mg/ml and 5 mg/ml for tobramycin. The eluted antibiotic concentrations were determined by the fluorescence polarization immunoassay. Initially large quantities of antibiotics were quickly eluted, depending on the amount of antibiotic mixture. A measurable amount of vancomycin was released for 3 days. There was no difference between the elution kinetics of the two antibiotics from the three different soaked grafts (p>0.05). Antibiotic-soaked grafts provided zones of inhibition against Staphylococcus aureus on Trypticase soy agar plate for up to 24 h. These results suggest that local application for 24 h of vancomycin or tobramycin with vascular grafts may be effective to prevent graft infection as shown by the fluorescence polarization immunoassay.