2005 Abstract : BS 2

Authors: Alt V, Steinr├╝cke P; Bechert T; Meissner SA;Seidel P; Wenisch S; Domann E; Schnettler R

Title: Nanoparticulate Silver Bone Cement Reduces Infection Rates in a Rabbit Model with Multiresistant Staphylococcus Aureus

Addresses: Department of Trauma Surgery, University Hospital Giessen, Germany

Purpose: Infections in bone and joint surgery, particularly with multiresistant bacteria, are a serious problem. A new nanoparticulate silver cement had previously shown good biocompatibility combined with good in vitro antimicrobial activity even against multiresistant bacteria.
The purpose of the current study was to evaluate the antibacterial activity of nanoparticulate silver cement against biofilm-building methicillin-resistant S. aureus (MRSA) in a rabbit model and to compare it to that of gentamicin-loaded cement.

Methods: Gentamicin cement or nanoparticulate silver bone cement was injected into the proximal half of one femur in 10 animals, respectively. Before hardening of the cement 107 or 108 colony forming units of MRSA with high gentamicin resistance were inoculated at the cement bone interface in 5 rabbits of each group. The animals were euthanized after 14 days and the cement adjacent bone was studied using microbiological and histological methods.

Results: Infections rates were 100% for the gentamicin group (10 of 10 animals had infection) and 30% for the NanoSilver group (3 of 10 animals). The inoculated MRSA strain was always the infect causing bacteria in case of infection as revealed by pulse gel electrophoresis. Thus, nanoparticulate silver bone cement significantly reduced infection rates by 70%. Histology showed diffuse osteolysis, reactive subperiostal new bone formation, and bone sequesters in the infected femora. MRSA colonies were also seen in case of infection.

Discussion: After inoculation the bacteria can run down intramedullary into the distal half femur of the femur where there is no antimicrobial effect of the bone cement because only the proximal half of the femur is filled by cement. This fact combined with the high inoculation dose of 107 or 108 colony forming units is the most likely reason for the occurrence of three infections in the silver group. Nanoparticulate silver was superior to gentamicin-loaded bone cement regarding the antimicrobial effect against MRSA. In the gentamicin group an infection rate of 100 % was found attributable to the high gentamicin resistance of the used strain. Gentamicin resistant bacteria are gaining importance in bone and joint surgery and therefore this new particulate silver bone cement may have a high interest in the futureicance

Significance: Animal Study