[Capsule formation in Staphylococcus aureus as a reason for nontypability by phages (author's transl)].

In Staph. aureus strains isolated from human pathological material the frequency of strains which did not react with typing phages (NT-strains) was found to be about 30%. In one half of the NT strains the reaction with typing phages is prevented by a capsule. The capacity for capsule-formation is lost after propagation of the cells in a liquid glycerol-minimal-medium; thus the cells become typable by phages. The capacity for capsule-formation can be restored after intraperitoneal injection into mice. A new propagation in glycerol-minimal-medium leads again to a loss of the capsule.