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AIM:To develop a polymerase chain reaction (PCR) for the specific detection of the C protein gene in strains of group B Streptococcus. METHODS:A single primer pair derived from the nucleotide sequence of the IgA binding beta antigen of the C protein complex permitted the specific amplification of a 592 base pair DNA fragment from the C protein gene. After 35 cycles of amplification this product could be detected by agarose gel electrophoresis. Southern blot hybridisation confirmed that this product was the C protein gene. RESULTS:PCR detected the C protein gene in 75 (63%) of 119 strains of group B streptococci analysed. The product was not detected in other Gram positive organisms, showing that this PCR assay was highly specific. The sensitivity of the assay was satisfactory to a dilution of 1 in 10,000 of extracted DNA. CONCLUSIONS:The C protein of group B streptococci is associated with neonatal sepsis. The specific detection of the C protein gene by PCR may help identify which strains are likely to be associated with infection by the organism.

Original publication





Journal of clinical pathology

Publication Date





633 - 636


Department of Medical Microbiology, St Bartholomew's Hospital, West Smithfield, London.


Streptococcus agalactiae, Bacterial Proteins, Blotting, Southern, Sensitivity and Specificity, Polymerase Chain Reaction, Nucleic Acid Hybridization, Gene Amplification, Base Sequence, Genes, Bacterial, Molecular Sequence Data