Optimization of the resistance of arterial allografts to infection: comparative study with synthetic prostheses

Arterial allografts can be used for in situ treatment of prosthetic graft infection. The purpose of this in vitro study was to compare the resistance of allografts and synthetic prostheses to infection by five strains of bacteria and to study antibiotic treatments designed to reduce allograft infection. Fresh and cryopreserved allografts were compared with synthetic prostheses made of various biomaterials including PTFE, plain Dacron, gelatine-sealed Dacron, and gelatine-sealed, rifampicine-bonded Dacron. Allografts were used with or without treatment using an antibiotic containing gentamycine, lincomycine, and vancomycine. The bacterial strains tested were Escherichia coli, Staphylococcus aureus, slime-producing Staphylococcus epidermidis, non-slime-producing Staphylococcus epidermidis, and Pseudomonas aeruginosa. Infection was evaluated by counting the number of adherent bacteria on the allograft or synthetic material after rinsing and ultrasonication. Statistical analysis was achieved using nonparametric Mann-Whitney tests. Results showed that allografts not treated with antibiotics were highly susceptible to bacterial infection. Antibiotic treatment decreased infection. Application of antibiotic after thawing cryopreserved allografts led to a significant decrease. None of the biomaterials tested provided sufficient protection against bacteria resistant to the antibiotics used.