Antibiotic efficacy against Staphylococcus epidermidis adherent to vascular grafts

Antibiotic bonded grafts may improve the treatment results of vascular graft infections. The purpose of this study was to determine the antibiotic and antibiotic concentration needed to be effective against Staphylococcus epidermidis-infected vascular grafts. The efficacy of four antibiotics (minocycline, cefazolin, vancomycin, and rifampin) against S. epidermidis adherent to Dacron or Teflon vascular grafts was studied in vitro. Kill kinetic studies were performed with 18 and 42 hr of exposure of Dacron-adherent and Teflon-adherent S. epidermidis at 1, 4, 16, and 64 times the minimum inhibitory concentration (MIC) of each antibiotic. Antibiotic efficacy against graft-adherent S. epidermidis at 42 hr was best at concentrations 64x MIC for minocycline, cefazolin, and vancomycin and 4x MIC for rifampin. None of the antibiotics totally eradicated the graft-adherent bacteria. Antibiotics were equally effective for S. epidermidis adherent to Dacron and Teflon grafts. Antibiotic concentrations several times that predicted by the MIC were needed for all antibiotics to achieve significant killing of graft-adherent bacteria, with rifampin the most effective at the lowest concentration.