Teichoic Acid Serologic Diagnosis of Staphylococcal Endocarditis

Using both double diffusion in agar and counterimmunoelectrophoresis, precipitating antibodies against staphylococcal teichoic acids were studied in 26 parenteral drug users with staphylococcal endocarditis at different times during their disease and in three control groups. The gel diffusion method was less sensitive (85% positive reactions in patients with endocarditis) but very specific (less than 5% false-positive reactions), whereas the more rapid (results in 40 minutes) counterimmunoelectrophoretic method was more sensitive (96% positive reactions in patients with endocarditis) and less specific (up to 10% false-positive reactions in drug-using controls). The use of both methods permits very accurate diagnostic differentiation between patients with endocarditis and "false-positives." Patients with staphylococcal endocarditis develop a prompt enough antibody response to be diagnostically helpful on admission to the hospital. With successful therapy over the ensuing weeks, the antibody titer declines and disappears. Some cross-reactions in patients with streptococcal endocarditis do occur.