PROTEIN A PRODUCTION IN DIFFERENT STRAINS OF STAPHYLOCOCCUS AUREUS UNDER VARIED GROWTH CONDITIONS

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Abstract
The protein A content of extracts of staphylococcal cells was estimated by the single radial immunodiffusion technique (Mancini technique) and by a haemagglutination test. The grouping of S. aureus strains according to protein A production using these methods was essentially similar to that based on their different affinity to FITC‐labelled immunoglobulins. High yields of protein A were obtained from staphylococcal cells which were harvested after growth on solid medium and extracted in 0.07 M phosphate buffer at pH 5.9 for 10 days at room temperature. The presence of sodium chloride (7.5 per cent) in the medium suppressed the formation of protein A. The immunogenic properties of both protein A producing strains and protein A were dependent on the presence or absence of serum (IgG) in the medium. Due to the complex formation between protein A and IgG, even highly purified protein A induced antibodies which reacted specifically with immunoglobulins when serum or blood had been present in the medium.