Evaluation of the Deeplex® Myc-TB Assay: A major advance in mycobacterial diagnosis and drug resistance detection
The rapid and accurate diagnosis of mycobacterial infections remains a major public health challenge. Distinguishing bacteria belonging to the Mycobacterium tuberculosis complex (MTBC), which causes tuberculosis, from nontuberculous mycobacteria (NTM) is essential for guiding treatment decisions and implementing appropriate control measures. In this context, next-generation sequencing (NGS) technologies are opening new diagnostic opportunities.
A recent study evaluated the performance of the Deeplex® Myc-TB assay, an innovative targeted NGS tool developed to identify mycobacterial species while simultaneously detecting mutations associated with antimicrobial resistance.
Study methodology
Researchers analyzed 304 positive mycobacterial cultures collected between May 2024 and March 2025. Among these, 273 samples yielded interpretable results, including:
- 29 isolates belonging to the Mycobacterium tuberculosis complex (MTBC);
- 244 isolates of nontuberculous mycobacteria (NTM).
The assay’s performance was compared with several reference methods:
- GeneXpert MTB/RIF for MTBC identification;
- Phenotypic drug susceptibility testing (pDST);
- MALDI-TOF mass spectrometry for NTM identification.
Key Findings
Tuberculosis Identification
The Deeplex® Myc-TB assay demonstrated 100% concordance with GeneXpert for the identification of Mycobacterium tuberculosis complex isolates. This performance confirms its reliability for tuberculosis diagnosis.
Detection of drug resistance
Among the 29 tuberculosis isolates analyzed:
- 18 (62.1%) showed no detectable resistance-associated mutations;
- 11 (37.9%) carried at least one resistance-associated mutation;
- 7 of these 11 isolates harbored mutations known to confer clinically significant resistance.
The genotypic results generated by Deeplex® Myc-TB were fully consistent with phenotypic drug susceptibility testing whenever validated interpretative criteria were available. The study also identified one case of multidrug-resistant tuberculosis (MDR-TB).
Identification of nontuberculous Mycobacteria
For the 244 NTM isolates, concordance with MALDI-TOF identification reached 98.8%.
The assay also enabled more detailed characterization, often down to the subspecies level, representing a significant advantage for clinical management.
The most frequently identified species were:
- The Mycobacterium avium complex (68% of isolates);
- The Mycobacterium abscessus group (26.6%);
- Several less common species, including xenopi, M. marinum, and M. haemophilum.
Clinical Relevance
One of the major strengths of the Deeplex® Myc-TB assay highlighted in the study is its ability to provide, through a single test:
- Accurate identification of mycobacterial species;
- Detection of resistance-associated mutations;
- High taxonomic resolution for NTM isolates.
This integrated approach reduces the need for multiple sequential analyses, which are often time-consuming and costly. As a result, clinicians can obtain critical information more rapidly, enabling timely treatment adjustments and helping to prevent the spread of resistant strains.
Conclusion
This study demonstrates that the WHO-recommended Deeplex® Myc-TB assay is a highly effective diagnostic tool for clinical microbiology laboratories. Thanks to its excellent accuracy in mycobacterial identification and its ability to simultaneously detect antimicrobial resistance mutations for the MTBC, it has the potential to improve the management of patients with tuberculosis and nontuberculous mycobacterial infections.
The integration of targeted sequencing into routine laboratory practice therefore represents a promising development for accelerating diagnosis, optimizing treatment strategies, and strengthening microbiological surveillance of mycobacterial infections.