Detection of protein A-like substances on haemolytic streptococci prior to use in mixed reverse passive antiglobulin haemagglutination (MRPAH).

Before mixed reverse passive antiglobulin haemagglutination tests (MRPAH) can be used to measure the class of bacterial antibodies, the bacteria have to be shown to be free of Protein A or Protein A-like substances on their surfaces. Two basic procedures have been examined: haemagglutination of red cells coated with immunoglobulin by the bacteria, and the MRPAH reaction itself to reveal absorption of purified gamma Fc by the bacterial suspension. The use of a purified gamma Fc component has proved successful in providing a sensitive test for the detection of Protein A-like substances on the surface of bacterial. In addition to both the Cowan and Wood strains of Staph, aureus, strains of haemolytic streptococci of groups A, C and G had Protein A-like substances on their surfaces. In contrast, strains of group B and group D, as well as Strep. milleri, had no detectable Protein A-like activity.