New fast test separates human and animal tuberculosis strains

Zoonotic tuberculosis caused by Mycobacterium bovis (Mb) is a neglected form of TB that makes global eradication harder because it looks clinically like human TB and needs different treatment considerations. Scientists led by Ana M. S. Guimarães set out to develop a rapid, high‑throughput test that can tell Mb apart from Mycobacterium tuberculosis (Mtb) isolates. Their goal was to improve diagnostics and surveillance for zoonotic TB in places where animal-derived infections complicate control efforts. To do this they turned to Fourier Transform Infrared Spectroscopy (FT-IRS) and the IR Biotyper® system, applying the technique directly to bacterial material instead of relying on DNA extraction. The study first compared two ways to inactivate the bacteria—paraformaldehyde and boiling—using Mtb and BCG strains grown in liquid culture. Both approaches produced material suitable for FT-IRS, but boiling was chosen because it was simpler and recovered biomass more efficiently. With an inactivation method selected, the team moved on to analyze clinical isolates and to test whether FT-IRS could provide a reliable, rapid fingerprint to separate these tuberculous mycobacteria.

The researchers used FT-IRS to collect spectral fingerprints from Mtb, Mb and a small number of Mycobacterium africanum (Maf) strains. Early work with Mtb and BCG strains confirmed that both paraformaldehyde and boiling allowed spectra to be collected, but boiling made sample preparation easier and improved biomass recovery for analysis. Spectra from clinical isolates were then fed into machine learning approaches to build classifiers. Linear Discriminant Analysis (LDA) and a UPGMA dendrogram showed clear separations between Mtb and Mb ecotypes, demonstrating that the infrared signatures were distinct. The team also trained and internally validated a classifier using artificial neural networks, which achieved 99% accuracy in distinguishing Mb from Mtb in their dataset. Further FT-IRS analysis of the few available Maf strains indicated the method could distinguish Maf from both Mtb and Mb, suggesting broader applicability to other tuberculous mycobacteria. This study is the first to apply FT-IRS to separate tuberculous mycobacteria using the IR Biotyper® platform.

These findings suggest FT-IRS could become a fast, accurate tool for differentiating Mb and Mtb in clinical or laboratory settings. Because Mycobacterium bovis is often resistant to pyrazinamide and causes more extrapulmonary disease, knowing whether an infection is caused by Mb or Mtb has direct consequences for treatment and public health response. FT-IRS offers advantages noted by the authors: it removes the need for DNA extraction, requires less technical expertise than some molecular tests, and provides rapid results suitable for higher-throughput workflows. The ability to distinguish Mycobacterium africanum (Maf) as well expands usefulness in regions where Maf is endemic. If further validated, this approach could strengthen surveillance for zoonotic TB, help target appropriate therapy, and make it easier for laboratories with limited resources to identify and track different TB-causing mycobacteria.