Preventing Implant-Associated Infections By Silver Coating

Implant-associated infections (IAIs) are a dreaded complication mainly caused by biofilm-forming staphylococci. Implant surfaces preventing microbial colonization would be desirable. We examined the preventive effect of a silver-coated titanium-aluminum-niobium (TiAlNb) alloy. The surface elicited a strong, inoculum-dependent activity against Staphylococcus epidermidis and Staphylococcus aureus in an agar inhibition assay. Gamma sterilization and alcohol disinfection did not alter the effect. In a tissue cage mouse model, silver coating of TiAlNb cages prevented perioperative infections in an inoculum-dependent manner and led to a 100% prevention rate after challenge with 2 x 10(6) CFU of S. epidermidis per cage. In S. aureus infections, silver coating had only limited effect. Similarly, daptomycin or vancomycin prophylaxis alone did not prevent S. aureus infections. However, silver coating combined with daptomycin or vancomycin prophylaxis thwarted methicillin-resistant S. aureus infections at a prevention rate of 100% or 33%, respectively. Moreover, silver release from the surface was independent of infection and occurred rapidly after implantation. On day 2, a peak of 82 mu g Ag/ml was reached in the cage fluid, corresponding to almost 6x the MIC of the staphylococci. Cytotoxicity toward leukocytes in the cage was low and temporary. Surrounding tissue did not reveal histological signs of silver toxicity. In vitro, no emergence of silver resistance was observed in several clinical strains of staphylococci upon serial subinhibitory silver exposures. In conclusion, our data demonstrate that silver-coated TiAlNb is potent for prevention of IAIs and thus can be considered for clinical application.