IgG antibody response in bacterial endocarditis using ELISA with multiple antigens

By means of enzyme-linked immunosorbent assays (ELISAs) the antibody responses were detected in sera from normal persons (n = 275), patients with various types of bacteremia (n = 137), and patients with endocarditis (n = 28). Four ELISAs were evaluated. As antigens ultrasonic extracts of Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, and nonhemolytic streptococci were used. The antibody levels against S. aureus increased with age, while antibodies against the other bacteria showed no age variation. The different ELISA systems showed many serological cross-reactions. The ELISA in this limited material was 72% successful in identifying cases of bacterial endocarditis caused by S. aureus (diagnostic sensitivity 84%; diagnostic specificity 89%), while in other cases of bacterial endocarditis it was less successful.