Comparative genomics of Neisseria meningitidis strains: new targets for molecular diagnostics

In 2010, Jaton et al. (False-negative PCR result due to gene polymorphism: the example of Neisseria meningitidis. J Clin Microbiol 2010;48:4590-2) reported an isolate of Neisseria meningitidis serogroup B that was not detected by the ctrA quantitative real-time PCR (qRT-PCR) used in our diagnostic laboratory. Sequence analysis of ctrA revealed several single nucleotide polymorphisms responsible for the negative qRT-PCR. Therefore, we sequenced the genome of this isolate and performed comparative genomics to propose new gene targets for the specific detection of N. meningitidis from clinical specimens. We identified 11 genes as specific to N. meningitidis genomes and common to at least 177 (97%) of the 183 genomes available. Among them, three genes (metA, tauE and shlA) were selected to develop new qRT-PCRs for the detection of N. meningitidis DNA. The three qRT-PCRs were highly sensitive and specific, and they exhibited a good reproducibility when tested on plasmidic positive controls and genomic DNA extracted from strains of N. meningitidis and other relevant bacterial species. The clinical sensitivity and specificity of metA and tauE qRT-PCRs were both 100% based on a testing of cerebrospinal fluid samples positive for N. meningitidis or other clinically relevant bacteria. Despite a 100% specificity, the sensitivity of the shlA qRT-PCR was only 70%. We thus recommend using the metA and/or tauE qRT-PCRs developed here. To prevent PCR failure in the presence of new polymorphic strains, the detection of dual targets by duplex qRT-PCR would be more accurate and suitable for the diagnosis of N. meningitidis from clinical specimens.