POTENTIAL OF EXOCELLULAR CARBOHYDRATE ANTIGENS OF STAPHYLOCOCCUS-EPIDERMIDIS IN THE SERODIAGNOSIS OF ORTHOPEDIC PROSTHETIC INFECTION

The potential of exocellular carbohydrate antigens of Staphylococcus e pidermidis as markers of infection in bone was investigated by immunob lotting and enzyme-linked immunosorbent assay (ELISA). Exocellular ant igens were prepared by gel filtration chromatography of concentrated b rain heart infusion culture supernates. The antigenic material appeare d as diffuse bands between 24 and 32 kDa on the immunoblots and was no t susceptible to digestion with trypsin, indicating that the response in the patients was to non-protein (polysaccharide or teichoic acid, o r both) exocellular material. Significant differences were detected be tween 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 i nfection showed an elevated serum IgG level by ELISA compared with con trols with uninfected joints. However, the antigen was not specific fo r S. epidermidis bone infection; high levels of IgG were also detected in patients with other serious staphylococcal and streptococcal infec tions. The ELISA test may be valuable in distinguishing between staphy lococcal infection of joints and aseptic loosening by excluding cases of infection.