DOI: 10.4103/bbrj.bbrj_54_26 ISSN: 2588-9834

Evaluation of Matrix-assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry in Comparison with MPT64 Antigen Test and Multiplex Polymerase Chain Reaction for Mycobacterial Culture Identification

Melreena Serra, M. Suchitra Shenoy
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Background:

Accurate and rapid identification of Mycobacterium species is essential for timely diagnosis and appropriate treatment of tuberculosis and nontuberculous mycobacterial (NTM) infections. Conventional methods are time-consuming and can have limited sensitivity, while Matrix-assisted Laser Desorption Ionization–Time of Flight (MALDI-TOF) mass spectrometry offers the potential for fast and precise species-level identification.

Methods:

This is a cross-sectional study conducted in the laboratory of a tertiary care hospital. The study included all the mycobacterial culture-positive samples identified by MALDI-TOF over 6 months. The effectiveness of MALDI-TOF Mass Spectrometry (MALDI TOF MS) was compared with the MPT64 antigen detection test and multiplex polymerase chain reaction.

Results:

Out of 836 samples received for acid-fast bacilli culture, 72 samples tested positive for the culture, with 68 (94.4%) accurately identified as various species of Mycobacterium and Nocardia using MALDI-TOF. Four samples could not be identified, as they failed to grow on Löwenstein-Jensen media on subculture. Among the identified samples, 41 were Mycobacterium tuberculosis complex (MTBC). Other findings included 24 NTMs: 10 Mycobacterium abscessus , 7 Mycobacterium fortuitum , 2 Mycobacterium intracellulare , 3 Mycobacterium gordonae , 1 each Mycobacterium oxidans , Mycobacterium margaritense, and 2 Nocardia cyriacigeorgica and 1 Nocardia farcinica . MALDI TOF MS showed high specificity at the species level, as it reliably differentiated MTBC and NTM and Nocardia Species with no evidence of misidentification.

Conclusion:

MALDI-TOF offers a rapid, easy, and cost-effective method for identifying mycobacterial species, typically requiring specialized laboratories. This technique involves minimal handling and reduces working hours, thereby lowering the risk of laboratory-acquired infections. Our study substantiates that MALDI-TOF is a reliable and fast option for NTM identification. However, standardizing the procedure with liquid media inoculated with clinical specimens is essential to further reduce diagnosis time.

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