The optimization of a blood-based assay for diagnosing tuberculosis which has been developed and validated in Dr. Hu’s lab, at Arizona State University, is important for ensuring its successful translation to a resource-limited setting of the developing world. Tuberculosis is most prevalent in the developing world with Sub-Saharan Africa having the highest cases of HIV/TB coinfections. The implementation of a blood-based assay for diagnosing Tuberculosis in the sub-Saharan would significantly improve the diagnosis and treatment monitoring of tuberculosis thereby managing or eliminating the pandemic altogether. The World Health Organization has called for robust diagnostic technologies that would resolve the shortfalls of the current technologies which include GeneXpert, X-ray, and smear microscopy. The blood-based diagnostic methodology heavily relies on Mass-spectrometry, a technology which could be entirely novel and expensive to implement in most laboratories in the Sub-Saharan. Despite virtual challenges in implementing the technology, the assay has demonstrated high specificity and sensitivity to HIV/TB coinfected patients and children in comparison to the available TB diagnostic assays. This study endorses the Blood-based Mass Spectrometry assay as one of the promising technologies to effectively improve the diagnosis of TB. The performance of the assay on detecting TB antigens was tested using different methods and materials. In the end, the use of DBS and miniaturized mass spectrometers have been discussed as possible routes for translating the assay to the developing world

Background: Nontuberculous mycobacteria (NTM)-mediated infections are a growing cause of worldwide morbidity, but lack of rapid diagnostics for specific NTM species can delay the initiation of appropriate treatment regimens. We thus examined whether mass spectrometry analysis of an abundantly secreted mycobacterial antigen could identify specific NTM species.

Methods: We analyzed predicted tryptic peptides of the major mycobacterial antigen Ag85B for their capacity to distinguish Mycobacterium tuberculosis and three NTM species responsible for the majority of pulmonary infections caused by slow-growing mycobacterial species. Next, we analyzed trypsin-digested culture supernatants of these four mycobacterial species by liquid chromatography–tandem mass spectrometry (LC–MS/MS) to detect candidate species-specific Ag85B peptides, the identity of which were validated by LC–MS/MS performed in parallel reaction monitoring mode.

Results: Theoretical tryptic digests of the Ag85B proteins of four common mycobacterial species produced peptides with distinct sequences, including two peptides that could each identify the species origin of each Ag85B protein. LC–MS/MS analysis of trypsinized culture supernatants of these four species detected one of these species-specific signature peptides in each sample. Subsequent LC–MS/MS analyses confirmed these results by targeting these species-specific Ag85B peptides.

Conclusions: LC–MS/MS analysis of Ag85B peptides from trypsin-digested mycobacterial culture supernatants can rapidly detect and identify common mycobacteria responsible for most pulmonary infections caused by slow-growing mycobacteria, and has the potential to rapidly diagnose pulmonary infections caused by these mycobacteria through direct analysis of clinical specimens.