title: Single-tube mixed agglutination test for the detection of staphylococcal protein A.
abstract: A simple, rapid mixed agglutination test using sheep erythrocytes (SRBC) sensitized with rabbit hemolysin and intact viable staphylococci is described for the detection of bound staphylococcal protein A. Soluble protein A was heat extracted from 50 clinical isolates as well as the Cowan I and Wood 46 strains of Staphylococcus aureus and titered by a hemagglutination test using sensitized SRBC and dilutions of soluble protein A. Protein A could be detected in all of these supernatants including that of S. aureus Wood 46, a strain generally considered to be protein A negative. These organisms were later retested by the mixed agglutination test and even those staphylococcal isolates expressing very low heat-extractable soluble protein A concentrations (1:2 titers) were positive, confirming the sensitivity of the test. In a screen of clinical isolates, only 4 of 235 (1.8%) coagulase-positive isolates were negative in the mixed agglutination test. Of 25 coagulase-negative isolates, none yielded a positive reaction.
mesh_terms: D000372:Agglutination Tests; D001426:Bacterial Proteins / Q000032:analysis*; D003030:Coagulase / Q000378:metabolism; D013210:Staphylococcus / Q000032:analysis* / Q000201:enzymology; D013211:Staphylococcus aureus / Q000032:analysis* / Q000201:enzymology
chemical_list: D001426:Bacterial Proteins; D003030:Coagulase