Solid-phase radioimmunoassay of immunoglobulin G antibodies to Staphylococcus aureus peptidoglycan in patients with staphylococcal infections.

A solid-phase radioimmunoassay (SPRIA) for determination of antibodies against S. aureus peptidoglycan was used for serological diagnosis of staphylococcal infections. Elevated IgG antibody levels were found in 21/21 patients with S. aureus endocarditis and in 10/24 patients with S. aureus septicemia. Two patients with streptococcal and one patient with pneumococcal septicemia showed elevated antibody levels as well, probably due to cross reactions between peptidoglycans of different bacterial species. In cases of chronic osteomyelitis caused by S. aureus, 12/33 patients showed elevated antibody levels while all patients with recurrent furunculosis had normal antibody levels. Anti-peptidoglycan antibodies were also found in all healthy controls (n = 160) but at lower levels. This might explain the rapid booster response of IgG antibodies found in 73 per cent of patients with S. aureus endocarditis already within 10 days after the first symptoms. The best clinical value of the assay seems to be in separating S. aureus endocarditis from uncomplicated septicemia.