Molecular detection of pre-ribosomal RNAs of Mycobacterium bovis bacille Calmette-Guérin and Mycobacterium tuberculosis to enhance pre-clinical tuberculosis drug and vaccine development

Efforts are underway globally to develop effective vaccines and drugs against M. tuberculosis (Mtb) to reduce the morbidity and mortality of tuberculosis. Improving detection of slow-growing mycobacteria could simplify and accelerate efficacy studies of vaccines and drugs in animal models and human clinical trials. Here, a real-time reverse transcription PCR (RT-PCR) assay was developed to detect pre-ribosomal RNA (pre-rRNA) of Mycobacterium bovis bacille Calmette-Guérin (BCG) and Mtb. This pre-rRNA biomarker is indicative of bacterial viability. In two different mouse models, the presence of pre-rRNA from BCG and Mtb in ex vivo tissues showed excellent agreement with slower culture-based colony-forming unit assays. The addition of a brief nutritional stimulation prior to molecular viability testing further differentiated viable but dormant mycobacteria from dead mycobacteria. This research has set the stage to evaluate pre-rRNA as a BCG and/or Mtb infection biomarker in future drug and vaccine clinical studies.