Identification of the psaA gene, coding for pneumococcal surface adhesin A, in viridans group streptococci other than Streptococcus pneumoniae

The gene encoding the pneumococcal surface adhesin A (PsaA) protein has bee n identified in three different viridans group streptococcal species. Compa rative studies of the psaA gene identified in different pneumococcal isolat es by sequencing PCR products showed a high degree of conservation among th ese strains. PsaA is encoded by an open reading frame of 930 bp. The analys is of this fragment in Streptococcus mitis, Streptococcus oralis, and Strep tococcus anginosus strains revealed a sequence identity of 95, 94, and 90%, respectively, to the corresponding open reading frame of the previously re ported Streptococcus pneumoniae serotype 6B strain. Our results confirm tha t psaA is present and detectable in heterologous bacterial species. The pos sible implications of these results for the suitability and potential use o f PsaA in the identification and diagnosis of pneumococcal diseases are dis cussed.