Type specificity and purification of the capsular antigen of a major type of Staphylococcus aureus

The Smith diffuse variant and the wound mucoid strain of Staphylococcus aureus were shown to exhibit serologically distinct capsules. The Welwood and K-6 strains of S. aureus were tested to determine their capsular types. Both Welwood and K-6 were found to be representative of the Smith capsular type. An additional 13 isolated of S. aureus from mice were tested. Gel double-diffusion tests and immunoelectrophoresis of staphylococcal antigens disclosed the probable existence of at least two additional capsular types. Passive hemagglutination tests carried out with cells sensitized with 1 mg of antigen per ml showed a multiplicity of cross-reacting antigens. However, cells sensitized either with 0.1 or 0.05 mg of antigen per ml and reacted with antisera absorbed with 10 or 1 ug/ml of homologous antigen showed the presence of specific antigen of extracts from each strain of S. aureus. Corroborative evidence for multiplicity of capsular types was obtained by the specific capsular reaction. At least four capsular types of S. aureus were found. The prototypic strains for these antigens are the RLM or wound strain, the Smith diffuse strain, and mouse strains designated 36T and 43R. It was proposed to designated these types 1, 2, 3, and 4, respectively. Three serologically active components in partially purified capsular material (PPCM) from the wound strain S. aureus were separated by column chromatography on Sepharose 6B. Chemical analyses of the components following acid hydrolysis showed no significant qualitative differences in their amino acid contents. The 73-80 ml pool showed 37% glucosamine and 36% reducing sugars. A significant difference was noticed in the glucosamine and reducing sugar values of the 73-80 ml pool as compared with the other pools. Immunoelectrophoretic analysis showed the 73-80 ml pool contained a single serologically active component which migrated anodally. Gel diffusion investigations confirmed the presence of the same serologically active component in PPCM by showing the present of a reaction of identity between the PPCM and 73-80 ml pool when they were reacted with specific antiserum.. Antiserum absorption studies revealed that the 58-72 ml, 73-/0 ml, and 81-100 ml pools all contained capsular antigen. The most active pool in the anticapsular antibody absorption test was the 73-80 ml pool. This fraction was twice as active as the 58-72 ml pool and eight times more active than the 81-100 ml pool in the absorption of anticapsular antibodies.