Advances in the diagnosis of tuberculosis- Journey from smear microscopy to whole genome sequencing

Biorecognition and detection of antigens from Mycobacterium tuberculosis using a sandwich ELISA associated with magnetic nanoparticles

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is one of the 10 leading causes of death worldwide, especially in low-income areas. A rapid, low-cost diagnostic assay for TB with high sensitivity and specificity is not currently available. Bio-functionalized magnetic nanoparticles (MNPs) which are able to efficiently detect and concentrate biomolecules from complex biological samples, allows improving the diagnostic immunoassays. In this way, a proof-of-concept of MNP-based sandwich immunoassay was developed to detect various MTB protein antigens. The superficial and secretory antigenic proteins considered in this research were: CFP10, ESAT6, MTC28, MPT64, 38 kDa protein, Ag85B, and MoeX. The proteins were cloned and expressed in an E. coli system. Polyclonal antibodies (ab) against the recombinant antigens were elicited in rabbits and mice. Antibodies were immobilized on the surface of amine-silanized nanoparticles (MNP@Si). The functionalized MNP@Si@ab were tested in a colorimetric sandwich enzyme-linked immunosorbent assay (sELISA-MNP@Si@ab) to recognize the selected antigens in sputum samples. The selected MTB antigens were successfully detected in sputum from TB patients in a shorter time (~ 4 h) using the sELISA-MNP@Si@ab, compared to the conventional sELISA (~15 h) standardized in home. Moreover, the sELISA-MNP@Si@ab showed the higher sensitivity in the real biological samples from infected patients.

Whole Genome Sequencing in the Management of Non-Tuberculous Mycobacterial Infections

Infections caused by non-tuberculous mycobacteria (NTM) have been a public health problem in recent decades and contribute significantly to the clinical and economic burden globally. The diagnosis of infections is difficult and time-consuming and, in addition, the conventional diagnostics tests do not have sufficient discrimination power in species identification due to cross-reactions and not fully specific probes. However, technological advances have been made and the whole genome sequencing (WGS) method has been shown to be an essential part of routine diagnostics in clinical mycobacteriology laboratories. The use of this technology has contributed to the characterization of new species of mycobacteria, as well as the identification of gene mutations encoding resistance and virulence factors. Sequencing data also allowed to track global outbreaks of nosocomial NTM infections caused by M. abscessus complex and M. chimaera. To highlight the utility of WGS, we summarize recent scientific studies on WGS as a tool suitable for the management of NTM-induced infections in clinical practice.

Performance of QuantaMatrix Microfluidic Agarose Channel system integrated with mycobacteria growth indicator tube liquid culture

The QuantaMatrix Microfluidic Agarose Channel (QMAC) system was used for rapid drug susceptibility testing (DST). Here, we performed DST using QMAC integrated with the mycobacteria growth indicator tube (MGIT) liquid culture employing a specially designed cross agarose channel for the tuberculosis chip. MGIT-, QMAC-, and Löwenstein-Jensen (LJ)-DSTs were performed using 13 drugs. The protocol for QMAC-DST was optimized using the inoculum obtained after the disaggregation of Mycobacterium tuberculosis clumps in MGIT culture. The completion times of QMAC-DST and MGIT-DST were analyzed, and the results of all three DSTs were compared. Discrepant results were analyzed using line probe assays and DNA sequencing. Nontuberculous mycobacteria were distinguished using the ρ-nitrobenzoic acid inhibition test. The overall agreement rate of QMAT-DST and LJ-DST was 97.0% and that of QMAT-DST and MGIT-DST was 86.3%. An average turnaround time for DST was 5.4 days, which was considerably less than the time required for MGIT-DST. The overall time required to obtain DST results using QMAC-DST integrated with MGIT culture was an average of 18.6 days: 13.2 days for culture and identification and 5.4 days for DST. Hence, QMAC-DST integrated with liquid culture can be used to perform DSTs with short turnaround times and effective detection. KEY POINTS: • QMAC system can simultaneously perform phenotypic DST with 13 anti-TB drugs and PNB. • An optimized DST protocol led to a marked decrease in clumping in MGIT culture. • QMAC system integrated with MGIT liquid culture system reduced the turnaround time.