Mycobacterium tuberculosis is the primary bacteria responsible for tuberculosis, one of the most dangerous diseases, and top causes of death worldwide, as identified by the World Health Organization in a 2018 report. Diagnostic tools currently exist for identifying those who carry active or latent versions of the infection including chest radiographs, a Mantoux tuberculin skin test, or an acid-fast bacilli smear of sputum samples. These methods are standard in the medical community of high income countries, but pose challenges for lower-income regions of the world as well as vulnerable populations. The need for a rapid, inexpensive, and non-invasive method of tuberculosis detection is evident by the ten million that contracted and 1.6 million that died from TB in 2017 alone. In our study, we used a previously developed nanoplasmon-enhanced scattering technology combined with dark field microscopy in order to investigate the potential for a blood-based TB detection assay. Twenty-eight capture antibodies were screened using cell culture exosomes and human serum samples to identify candidates for a TB-derived exosome biomarker. Four antibodies demonstrated potential for distinguishing negative controls from positive controls in this study: anti-AG85, anti-AG85B, anti-SodA, anti-Ald. These capture antibodies displayed significant differences (p<0.05) for both cell culture exosomes and human serum samples on more than one occasion. The work is significant in its ability to distinguish potential capture antibody targets, and future experimentation may yield a technology ready for clinical settings to address the gap in current TB detection methods.

Background: HIV-associated immune defects inhibit tuberculosis (TB) diagnosis, promote development of extrapulmonary TB and paucibacillary pulmonary TB cases with atypical radiographic features, and increase TB relapse rates. We therefore assessed the diagnostic performance of a novel assay that directly quantitates serum levels of the Mycobacterium tuberculosis (Mtb) virulence factor 10-kDa culture filtrate protein (CFP-10) to overcome limitations associated with detecting Mtb bacilli in sputum or tissue biopsies.

Methods: This study analyzed HIV-positive adults enrolled in a large, population-based TB screening and surveillance project, the Houston Tuberculosis Initiative, between October 1995 and September 2004, and assigned case designations using standardized criteria. Serum samples were trypsin-digested and immunoprecipitated for an Mtb-specific peptide of CFP-10 that was quantified by liquid chromatography-mass spectrometry for rapid and sensitive TB diagnosis.

Results: Among the 1053 enrolled patients, 110 met all inclusion criteria; they included 60 tuberculosis cases (12 culture-negative TB), including 9 relapse TB cases, and 50 non-TB controls, including 15 cases with history of TB. Serum CFP-10 levels diagnosed 89.6% (77.3–96.5) and 66.7% (34.9–90.1) of culture-positive and culture-negative TB cases, respectively, and exhibited 88% (75.7–95.5) diagnostic specificity in all non-TB controls. Serum antigen detection and culture, respectively, identified 85% (73.4–92.9) and 80.0% (67.3–88.8) of all 60 TB cases.

Conclusions: Quantitation of the Mtb virulence factor CFP-10 in serum samples of HIV-infected subjects diagnosed active TB cases with high sensitivity and specificity and detected cases missed by the gold standard of Mtb culture. These results suggest that serum CFP-10 quantitation holds great promise for the rapid diagnosis of suspected TB cases in patients who are HIV-infected.

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.