Rapid clinical detection of mycobacterial infections using M-Typer and flow-injection tandem mass spectrometry.

OBJECTIVES: We evaluated the utility of the M-Typer® assay, based on flow-injection tandem mass spectrometry mycolic acid profiling, in the diagnosis of TB and other mycobacterial infections.

METHODS: The ability of the M-Typer® assay to identifyspecies was first evaluated using 40 clinical strains of known species. In the second phase, clinical specimens from 451 patients with suspected TB or non-tuberculous mycobacteria (NTM) infections were tested. Results were compared with those obtained from Xpert MTB/RIF and MGIT culture.

RESULTS: The M-Typer® assay correctly classified all clinical strains as eithercomplex or NTM, and 80% were accurately identified to species level. In clinical specimens, it showed high sensitivity (94.4%) and specificity (93.63%) for TB diagnosis compared to Xpert MTB/RIF. Similar values were observed versus MGIT culture (sensitivity: 93.75%; specificity: 95.77%). However, the assay's positive predictive value (PPV) was lower (70.8% vs. Xpert MTB/RIF; 45.45% vs. MGIT culture).

DISCUSSION: The M-Typer® assay demonstrated diagnostic accuracy comparable to established methods, supporting its potential role in clinical microbiology for rapid, direct detection and species-level identification of mycobacteria. Nevertheless, its relatively low PPV indicates the need for further optimisation and validation in diverse clinical settings.