At a Glance
Biomarkers, derived from either host or infectious agent are indicative not only of disease but also of disease stage, severity, and drug failure. Discovering new biomarkers from easily attainable bodily fluids is essential to control tuberculosis, a disease that kills 1.5 to 2 million individuals a year. Utilizing exosomes, researchers at Colorado State University in collaboration with the University of Notre Dame have patented a unique protein signature diagnostic for Mycobacterium tuberculosis (Mtb) having greater sensitivity, accuracy and speed than any current diagnostic technique.
Tuberculosis (TB) is a common and often lethal infectious disease caused by the Mycobacterium genus of bacteria, typically Mycobacterium tuberculosis (Mtb). Mtb is air transmissible and easily spreads between individuals through respiratory fluid droplets. Most Mtb infections are asymptomatic, latent TB infections (LTBI), however, some of these infections can eventually progress to active TB infections. TB typically infects the pulmonary system of an afflicted individual; however, the disease can also spread through the body causing extrapulmonary TB (EPTB). Left untreated, active TB typically kills more than half the individuals it affects.
It is estimated that one third of the entire global population is currently infected with Mtb. In 2007 alone, there were an estimated 8 million new cases of TB. During the same year, there were an estimated 1.7 million deaths attributed to TB. Active TB is particularly common in low to middle-income countries, accounting for roughly 80% of reported disease cases.
Given TB’s high prevalence and associated deaths, fast diagnosis and treatment of active TB is of paramount importance. Currently, the two most common methods of detecting Mtb infection are the sputum acid-fast bacilli smear microscopy test (AFB) and the tuberculin skin test (TST).
In AFB smears, sputum is collected from patients and the sample is examined microscopically after a bacterial staining procedure. Although AFB can produce presumptive results in a few hours, it suffers from poor sensitivity. AFB also fails to identify TB patients having little to no Mtb in their sputum or those patients who are unable to produce sputum – especially common in young children. Further, Mtb replicates slowly, making positive identification of Mtb in cultures lengthy, ranging from days to weeks.
TST is a composite measure of cell-mediated immunity in response to TB antigen (PPD) stimulation, which is injected under the skin of a patient. However, it may take 2 to 3 days before the results can be obtained and frequently delivers false positive or false negative results. Also, this test does not distinguish latent infection from active disease, which is important in a diagnostic setting.
A critical need exists for novel diagnostic and prognostic assays to identify those at risk for TB and capable of transmitting Mtb to other individuals.
- Robust and accurate results
- Potential as point-of-care test in high burden, low-income countries
C Mehaffy, et al. (2020) Identification of Mycobacterium Tuberculosis Peptides in Serum Extracellular Vesicles from Persons with Latent Tuberculosis Infection. J Clin Microbiol. 58(6):e00393-20. doi: 10.1128/JCM.00393-20.
Last updated: August 2021