Identification of Streptococcus pneumoniae by a real-time PCR assay targeting SP2020

Sci Rep. 2019 Mar 1;9(1):3285. doi: 10.1038/s41598-019-39791-1.

Abstract

Real-time PCR targeting lytA (the major autolysin gene) and piaB (permease gene of the pia ABC transporter) are currently used as the gold-standard culture-independent assays for Streptococcus pneumoniae identification. We evaluated the performance of a new real-time PCR assay - targeting SP2020 (putative transcriptional regulator gene) - and compared its performance with the assays previously described. A collection of 150 pneumococci, 433 non-pneumococci and 240 polymicrobial samples (obtained from nasopharynx, oropharynx, and saliva; 80 from each site) was tested. SP2020 and lytA-CDC assays had the best performance (sensitivity of 100% for each compared to 95.3% for piaB). The specificity for lytA and piaB was 99.5% and for SP2020 was 99.8%. Misidentifications occurred for the three genes: lytA, piaB and SP2020 were found in non-pneumococcal strains; piaB was absent in some pneumococci including a serotype 6B strain. Combining lytA and SP2020 assays resulted in no misidentifications. Most polymicrobial samples (88.8%) yielded concordant results for the three molecular targets. The remaining samples seemed to contain non-typeable pneumococci (0.8%), and non-pneumococci positive for lytA (1.7%) or SP2020 (8.7%). We propose that combined detection of both lytA-CDC and SP2020 is a powerful strategy for the identification of pneumococcus either in pure cultures or in polymicrobial samples.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Bacterial Proteins / genetics*
  • DNA, Bacterial / genetics*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Nasopharynx / microbiology*
  • Pneumococcal Infections / genetics*
  • Pneumococcal Infections / microbiology
  • Real-Time Polymerase Chain Reaction*
  • Streptococcus pneumoniae / genetics*

Substances

  • Bacterial Proteins
  • DNA, Bacterial