Antibody response against whole Staphylococcus aureus in patients with staphylococcal septicaemia and endocarditis investigated by ELISA.

A whole cell Staphylococcus aureus enzyme-linked immunosorbent assay (ELISA) for the detection of IgG antibodies against S. aureus has been developed. To avoid non-specific binding of IgG to protein A, the protein A-poor strains of S. aureus, E 1369 and Wood 46, were used as antigens. One-hundred and eighty serum samples from 120 patients with S. aureus endocarditis, non S. aureus endocarditis, S. aureus septicaemia and non S. aureus septicaemia were tested together with sera from 155 healthy controls. The sensitivity was similar for the E 1369 ELISA and the Wood 46 ELISA and positive test values were detected in 84.2% of patients with S. aureus endocarditis and 41.2% of patients with complicated S. aureus septicaemia. No distinction could be found between complicated and uncomplicated S. aureus septicaemia. The E 1369 ELISA was more specific showing cross reactions with sera from patients infected with other bacteria than S. aureus in 3.6%. Furthermore, the reproducibility was better for the E 1369 ELISA with a coefficient of variation at 0.054. The absence of need for purified antigens makes the whole S. aureus ELISA easy, rapid and cheap. Therefore, we suggest the whole S. aureus ELISA as a good alternative to previously reported assays using purified cell wall antigens.