Evaluation of several biochemical and molecular techniques for identification of Streptococcus pneumoniae and...

Area of Science:

• Clinical Microbiology
• Molecular Diagnostics
• Bacteriology

Background:

• Accurate identification of mitis group streptococci, including Streptococcus pneumoniae, is challenging due to limitations in current diagnostic assays.
• Distinguishing S. pneumoniae and Streptococcus pseudopneumoniae from other mitis group streptococci is critical for effective patient management and epidemiological studies.

Purpose of the Study:

• To evaluate the sensitivity and specificity of various biochemical and molecular assays for identifying S. pneumoniae and S. pseudopneumoniae.
• To compare the diagnostic performance of different methods, including traditional tests and molecular techniques, for mitis group streptococci detection.

Main Methods:

• Evaluation of biochemical tests (bile solubility, optochin susceptibility) and molecular assays (real-time multiplex PCR, gene sequencing, MALDI-TOF MS).
• Testing of 54 isolates from 53 respiratory specimens of patients with community-acquired pneumonia.
• Comparison of assay results against gold standard methods and molecular detection in clinical samples.

Main Results:

• A multiplex real-time PCR assay targeting Spn9802 and autolysin genes demonstrated high concordance with the gold standard bile solubility test.
• Several traditional methods (optochin susceptibility in O2, oxgall disk bile solubility, gene sequencing) yielded false-positive, false-negative, or inconclusive results.
• S. pseudopneumoniae isolates were only identifiable by molecular assays; the multiplex real-time PCR was most effective for both S. pneumoniae and S. pseudopneumoniae.

Conclusions:

• The multiplex real-time PCR assay is the most convenient and accurate method for identifying S. pneumoniae and S. pseudopneumoniae in clinical respiratory samples.
• Molecular detection using this PCR assay can identify S. pneumoniae and S. pseudopneumoniae DNA in samples where only other streptococci were cultured, suggesting broader detection capabilities.