Genotypic identification of presumptive Streptococcus pneumoniae by PCR using four genes highly specific for S. pneumoniae.

It was previously reported that two oligonucleotide primer sets (spn9802 and spn9828) for discriminating Streptococcus pneumoniae from pneumococcus-like oral streptococcal isolates using PCR had been developed. In this study, PCR amplification of the lytA, ply, spn9802 and spn9828 genes was used to identify presumptive S. pneumoniae. Two genetic groups were identified by analysing sputum samples from 28 patients with community-acquired pneumonia: the lytA-positive, ply-positive, spn9802-positive and spn9828-negative group, and the lytA-positive, ply-positive, spn9802-positive and spn9828-positive group. Isolates of the former group were resistant to optochin, while those of the latter group showed susceptibility to optochin. The lytA-positive, ply-positive, spn9802-negative and spn9828-negative isolates, and lytA-positive, ply-positive, spn9802-negative and spn9828-positive isolates, were not detected in sputum from patients with pneumonia. Subsequently, a total of 92 saliva samples from healthy individuals was screened by PCR using these primer sets. The lytA-positive, ply-positive, spn9802-positive and spn9828-negative group was identified more frequently in saliva from healthy children than in saliva from older healthy individuals and patients with pneumonia. The lytA-positive, ply-positive, spn9802-positive and spn9828-positive group was found frequently in saliva from healthy children, and in saliva and sputum from patients with pneumonia. This study demonstrates a rapid, optimal screening method for the genotypic identification of presumptive S. pneumoniae by PCR using four genes highly specific for S. pneumoniae.