(group B streptococci; GBS) are serotyped on the basis of the capsular polysaccharide antigens and subtyped on the basis of the strain-variable and surface-localised c proteins c, c, and R proteins. This study compared c protein detection and the polymerase chain reaction (PCR) for gene detection, by examining 50 clinical GBS strains. the c protein was detected by antibody-based immunofluorescence in a GBS whole-cell assay and Western blotting by probing with the anti-c; antibody or human IgA. Absorption experiments were performed to test for surface-anchoring of c; and bacterial supernates were examined to test for c production. Primers for the PCR target regions resulted in a 620-bp product that included gene-encoding IgA-binding domains. the results demonstrated four categories of GBS with respect to the gene and the c protein: (1) strains (16 of 50) that harboured the gene and regularly expressed normal surface-localised c with a M of 120 kDa; (2) strains (5 of 50) that harboured the gene but did not express the protein; (3) strains (2 of 50) that harboured the gene but expressed a c that was not surface-localised and had reduced M; (4) strains (27 of 50) without gene and c expression. One strain amongst the third group generated a PCR product of 1330 bp. These results demonstrate considerable strain variability of the gene of GBS and of its product the c protein.


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