Adherence of S. epidermidis on different metals. A comparative in vitro study

Aim: Staphylococcus epidermidis is the most common cause of orthopedic infections. Adhesion and biofilm formation on orthopedic implant surfaces play an important role in the physiopathology of these infections. The aim of our study was to evaluate the adhesion of S. epidermidis on the surface of metals usually used in orthopedics. Methods: Previously sterilized circular metal plates of titanium (Ti), porous titanium (p-Ti), cobalt chromium (CoCr) and stainless steel (SS) were hung completely submerged in a liquid medium with a known concentration of S. epidermidis (RP62A). They were incubated for 1 h or 24 h at 36 degrees C. After incubation, each plate was washed with PBS and sonicated during 5 minutes in 10 mL of saline. Different dilutions were performed and 100 mu L from each sample was cultured on agar plates. Results: 26 metal plates were incubated for 1 h and other 55 metal plates for 24 h. The lowest bacterial count (cfu/mm(2)) at 1 h was observed in CoCr plates while in p-Ti it was 6 times higher. At 24 h the highest bacterial count was observed in SS plates while the lowest in Ti. However, these differences were not statistically significant. Conclusions: After 1 h and 24 h of exposure, the lowest adherence was observed in CoCr and Ti plates, respectively. However, bacterial attachment occurred with all materials. It is necessary to further investigate new materials able to avoid bacterial attachment.