Direct testing of blood culture for detection of the serotype 5 and 8 capsular polysaccharides of Staphylococcus aureus.

Monoclonal antibodies (MAbs) reactive with serotype 5 and 8 capsular polysaccharides of Staphylococcus aureus have been used to test, by enzyme-linked immunosorbent assay (ELISA), blood culture fluids for the presence of S. aureus. A total of 748 blood cultures from 665 patients yielding 706 bacterial isolates belonging to more than 26 bacterial species were studied. All blood cultures containing bacterial strains belonging to species other than S. aureus were negative in ELISA. All 23 blood cultures containing serotype 5 S. aureus were positive in ELISA with the corresponding MAb. Out of 20 blood cultures containing serotype 8 S. aureus, 19 were positive with the corresponding MAb. All 5 blood cultures containing nontypeable S. aureus were negative in ELISA with both MAbs. This method provides reliable identification of serotype 5 or serotype 8 S. aureus by direct testing of blood culture fluids with ELISA.