Biochemical and biological properties of Staphylococcus aureus septicemia strains in relation to clinical characteristics.

166 Staphylococcus aureus septicemia strains were phage grouped and tested for lipolytic activity, protein A content, alpha, beta and delta hemolysin activity and toxic shock syndrome toxin (TSST-1) production. These strain characteristics were correlated to the clinical features of the infections. Patients infected with phage group II strains showed the lowest mortality but were more prone to develop internal abscesses. Lipolytic activity and protein A positivity was found in most strains and no correlation to phage group or clinical signs could be shown. Alpha hemolysin was the most common of the investigated hemolysins though it was only produced by 58% of 88 investigated strains. Beta and delta hemolysin production was found in 25% and 24% of the strains, respectively. The lowest frequency of alpha hemolysin production (25%) was found among phage group I strains, especially those producing TSST-1, where only 1 of 12 strains was positive. The overall frequency of TSST-1 production was 18% in 88 tested strains and most positive strains were non-hemolytic. These results indicate that hemolysin production does not seem to be required for a strain to be invasive.