Comparison of anti-alpha-haemolysin and teichoic acid antibody tests in patients with Staphylococcus aureus endocarditis or bacteraemia.

To assess the value of serological tests in differentiating endocarditis and complicated bacteraemia due to Staphylococcus aureus from uncomplicated S. aureus bacteraemia and from nonstaphylococcal endocarditis we measured teichoic acid antibodies (TAA) (by means of a gel diffusion method) and antibodies to alpha-haemolysin (ASta) in the serum of 22 patients with S. aureus endocarditis, 42 patients with complicated S. aureus bacteraemia, 21 patients with uncomplicated S. aureus bacteraemia, 27 patients with other than S. aureus endocarditis, 17 patients with culture-negative endocarditis and 337 non-infected control patients. TAA and ASta titres were found significantly more often in staphylococcal endocarditis than in non-staphylococcal endocarditis, 59 per cent versus 4 per cent for the TAA test and 32 per cent versus 0 per cent for the ASta assay. The combined use of the two tests proved best for differentiating the two groups of endocarditis from each other, 72 per cent versus 4 per cent respectively. In the culture-negative endocarditis group there were two serologically positive patients whose anti-staphylococcal antibiotic therapy based on the serological findings was successful, supporting the clinical usefulness of staphylococcal serological tests in endocarditis of unknown bacterial aetiology. The serological tests were not useful, however, in differentiating S. aureus endocarditis from complicated or uncomplicated bacteraemia due to S. aureus without endocarditis.