Molecular detection of incidental Mycobacterium tuberculosis and nontuberculous mycobacteria co-detections using DNA strip assay: a laboratory-based study

Overlapping clinical manifestations of Mycobacterium tuberculosis (MTB) detection and diseases caused by non-tuberculous mycobacteria (NTM) pose significant diagnostic challenges in tuberculosis-endemic settings. Conventional methods often fail to provide a discriminated diagnosis and/or detect co-detections; however, molecular assays enable precise species-level identification and simultaneous detection of multiple pathogens, thereby enabling detection of multiple mycobacterial species, including co-detection patterns. The purpose of this study is to evaluate the utility of molecular methods for detecting the incidental coexistence of MTB and NTM, thereby supporting improved laboratory-level identification. A total of 890 clinical samples from patients presumed to have a mycobacterial infection were evaluated. The test involved performing AFB smear microscopy, NAAT, MGIT, and MPT64 antigen testing, followed by analysis using the GenoType Mycobacterium CM/AS, which helped identify MTB complex as well as NTM, thus enabling us to identify accidental co-detections that would arise from MTB-NTM. Out of 890 samples analyzed, 27/890 (3.03%) samples turned out to be positive for NTM detection. In this study, 19/27 (70.3%) had only NTM detection, and 8/27 (29.6%) demonstrated MTB-NTM co-detection. Overall, co-detections accounted for 0.89% (8/890) of the total processed samples and 29.6% (8/27) of the samples positive for NTM. The most predominant species was M. fortuitum, which was followed by M. chelonae, and then a case of simultaneous detection with M. avium complex and M. fortuitum along with MTB. In general, it has been seen that M. fortuitum had the highest frequency in such cases. These findings are based on laboratory detection and should not be interpreted as evidence of confirmed co-infection.