Comparison of four polymerase chain reaction assays for specificity in the identification of Streptococcus pneumoniae

Abstract

We determined the usefulness of 4 conventional polymerase chain reaction (PCR) assays, lytA, psaA, and two primer sets from the ply gene, for accuracy in the discrimination of nontypeable (NT) Streptococcus pneumoniae from closely related atypical streptococci. The study used 100 strains. We compared the PCR results with laboratory tests that included optochin (ethylhydrocupreine hydrochloride) sensitivity, bile solubility, the Quellung reaction, and AccuProbe (Gen-Probe Inc., San Diego, CA). These latter tests did not discriminate the atypical streptococci from the NT pneumococci. All PCR primer sets amplified the NT pneumococcal isolates in agreement with the other laboratory tests. However, the IA and IB ply primers were positive for 8 of the 16 atypical streptococcal isolates, and the IIA and IIB ply primers amplified all atypical isolates. The psaA primers had only one discrepant result, a positive among the atypical streptococci. The lytA primers were the most specific with 100% specificity for all strains tested.