Immunochemical study of diverse surface antigens of a Staphylococcus aureus isolate from an osteomyelitis patient and their role in in vitro phagocytosis.

The cellular antigens of a strain of Staphylococcus aureus, isolated from a bone fragment from osteomyelitis, were analyzed immunochemically and by interaction with human phagocytic cells. When this strain was allowed to interact with human polymorphonuclear cells in the presence of antiserum, the strain was shown to have specific antiphagocytic antigens. An acidic polysaccharide consisting of galactose and glucuronic acid was isolated from the cell surface of the organism, and in vitro opsonization tests indicated that this acidic antigen impeded in vitro phagocytosis by human polymorphonuclear cells. It was also observed that antibodies directed against the mucopeptide constituents of homologous and heterologous bacterial cell walls were effective in promoting the in vitro opsonization of the organism. In the presence of antimucopeptide serum and human polymorphonuclear cells, a variant strain was isolated from the wild type, and immunochemical analysis indicated that this strain consisted of galactose and immunodominant amino-galacturonic acid residues. In vitro phagocytosis studies employing this variant strain indicated that the homologous human convalescent serum contained higher levels of opsonins against the variant strain than the original isolate, the wild type. This observation is discussed.