Infection at the site of implanted materials with and without preadhered bacteria

A study was undertaken to examine the role of bacterial adherence in the development of infection at the site of an implant. The amount of in vitro adherence of Staphylococcus epidermidis was greatest for stainless steel, followed by polymethylmethacrylate and commercially pure titanium, and was least for polymethylmethacrylate with gentamicin. These materials then were preincubated with S. epidermidis and implanted. The number of organisms that were isolated and the rate of infection followed the same pattern as that in the in vitro studies. Materials that were not preincubated with bacteria also were implanted and bacteria were injected into the site. The number of organisms isolated from the site and the rate of infection were lower than those for the preincubated materials, but the trend was the same as in both the in vitro and the in vivo studies. The rates of infection and colonization correlated with the propensity for the organisms to adhere to a given material. Materials colonized with S. epidermidis at the time of implantation caused a high rate of infection. The ability of organisms to adhere to a material in vitro is correlated with their propensity to cause biomaterial-based infection.