Performance verification of pre-PCR and real-time PCR step in the molecular diagnosis of pneumococcal meningitis cases

Abstract

Isolation and determination of s.pneumoniae by culture and serological methods can be time consuming or indeterminate. Molecular diagnosis by real-time PCR is independent of the growth of the pathogen causing meningitis, and is not diminished with non-viable organisms. The aim of this study was to evaluate the performance criteria of pre-PCR-TR DNA extraction step and PCR-TR step by targeting two genes encoding s.pneumoniae. In this study we evaluated the inter-sample contamination of the pre-PCR-TR step, the intermediate fidelity and the repeatability of the DNA essay. PCR-TR verification was performed by two genes targeting s. pneumoniae the Lyt A and SP 2038 gene; sensitivity, specificity and LLD were determined. Contamination rate had a value of less than 0%, which is in agreement with an absence of inter-sample contamination; the repeatability and intermediate fidelity have a cv˂7%. The evaluation of the sensitivity and specificity of the RT-PCR assays targeted 100% the Lyt A gene and the SP 2038 gene. The standard curve generated detected less than 10copies for the Lyt A gene and less than 100copies for the SP 2038 gene. This study showed that the pre-PCR and PCR-TR assays met the performance criteria targeted in this study.