Construction of a GBS-GAS DNA subtraction library allows discovery of previously unidentified GBS genes and rapid location of unique regions on the GBS chromosome.

A subtraction library of group B streptococcus (GBS) strain O9OR with GAS chromosomal DNA (strain SF370) was constructed and more than 100 plasmid clones sequenced. DNA sequences of the plasmid inserts were analyzed using the BLAST gene search. Most inserts had little or no homology to GAS chromosomal DNA and 26 clones from the library had no gene homologues in the gene bank. The majority of genes discovered represented house keeping GBS genes, but several could be considered as possible virulence factors. Inserts from 21 clones were labeled and used as probes for hybridization with GBS DNA fragments separated by pulsed field electrophoresis. A genetic map of GBS strain O9OR was constructed.