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

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Abstract
The cellular antigens of a strain of S. 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 [PMN] in the presence of antiserum, the strain had specific anti-phagocytic antigens [Ag]. 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 Ag impeded in vitro phagocytosis by human PMN cells. 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 anti-mucopeptide serum and human PMN cells, a variant strain was isolated from the wild type. 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.