Potential of exocellular carbohydrate antigens of Staphylococcus epidermidis in the serodiagnosis of orthopaedic prosthetic infection.

The potential of exocellular carbohydrate antigens of Staphylococcus epidermidis as markers of infection in bone was investigated by immunoblotting and enzyme-linked immunosorbent assay (ELISA). Exocellular antigens were prepared by gel filtration chromatography of concentrated brain heart infusion culture supernates. The antigenic material appeared as diffuse bands between 24 and 32 kDa on the immunoblots and was not susceptible to digestion with trypsin, indicating that the response in the patients was to non-protein (polysaccharide or teichoic acid, or both) exocellular material. Significant differences were detected between the immunoblot antigen profiles for serum IgG from patients with S. epidermidis bone infection and those with an uninfected prosthetic joint. Thirteen of 16 patients with S. epidermidis prosthetic joint infection showed an elevated serum IgG level by ELISA compared with controls with uninfected joints. However, the antigen was not specific for S. epidermidis bone infection; high levels of IgG were also detected in patients with other serious staphylococcal and streptococcal infections. The ELISA test may be valuable in distinguishing between staphylococcal infection of joints and aseptic loosening by excluding cases of infection.