title: Biological properties of the encapsulated Staphylococcus aureus M.
abstract: Strain M, classified as a Staphylococcus aureus, behaves like the other rare encapsulated staphylococcal strains. It was clumping-factor negative, grew in diffuse-type colonies in serum-soft agar, and produced rapidly fatal disease in mice. Strain M was highly resistant to phagocytosis by human or mouse leukocytes and required both specific antibody and heat-labile serum factor(s) for efficient ingestion by human polymorphonuclear leukocytes. Electron micrographs confirmed the presence of a large capsule. Agglutination studies, active or passive mouse protection experiments, and opsonic studies revealed that strain M represents a new, immunologically distinct strain of encapsulated staphylococcus. Strain M differs from other known encapsulated staphylococci in several other respects: its cellular and colonial morphology is atypical; its LD(50) in the mouse peritoneal model is 100 times less than that of other mouse lethal strains; it is poorly opsonized by normal human serum; and, finally, it possesses an unusually large capsule as seen in electron micrographs.
mesh_terms: D000372:Agglutination Tests; D000818:Animals; D000917:Antibody Formation; D001428:Bacterial Vaccines; D001431:Bacteriological Techniques; D003470:Culture Media; D007112:Immunity, Maternally-Acquired; D007114:Immunization; D051379:Mice; D008854:Microscopy, Electron; D009154:Mutation; D009895:Opsonin Proteins; D010587:Phagocytosis; D011817:Rabbits / Q000276:immunology; D013210:Staphylococcus / Q000145:classification / Q000276:immunology* / Q000472:pathogenicity; D014118:Toxins, Biological / Q000032:analysis; D014774:Virulence
chemical_list: D001428:Bacterial Vaccines; D003470:Culture Media; D009895:Opsonin Proteins; D014118:Toxins, Biological