A breakthrough that will save time in diagnosing resistance in cases of infection with Mycobacterium tuberculosis was announced May 13th by a team from University College London.  Instead of taking weeks to sequence an entire genome of a M. tuberculosis organism from laboratory grown cultures, this new method permits complete sequencing to be done in only a few days directly from sputum samples.  This novel approach uses biotinylated RNA probes directed at M. tuberculosis DNA.

Mycobacterium tuberculosis bacteria/CDC
Mycobacterium tuberculosis bacteria/CDC

The team led by Amanda Brown and Josephine Bryant which included researchers in the UK, the US and Denmark tested this new diagnostic technique against 24 samples of smear-positive samples, from patients in the UK and Lithuania, that had already been sequenced by conventional methods using culture, and two samples that had not been able to be grown in culture.

The new approach was able to sequence the genomes of all 24 culture grown samples (in twenty of these, sequencing was considered high-quality) yielding genomic analysis that accurately predicted phenoytypic resistance.  Furthermore, the new diagnostic method successfully yielded high-quality sequence results from one of the samples which could not be grown in the laboratory.

Outcomes for patients infected by drug-resistant strains should be greatly improved with faster diagnosis leading to appropriate drug-regimens implemented sooner.  Communities will benefit from rapid detection of resistance potential from emerging strains.

In addition, monitoring of outbreaks of tuberculosis will be advanced with more rapid, highly specific detection of unique strains afforded by this novel diagnostic technique.

Steven Smith, M.Sc. is an Infectious diseases epidemiologist