The time needed to genetically sequence the bacteria causing tuberculosis (Mtb) from patient samples has been reduced from weeks to days using a new technique. This could help health service providers to better treat disease, control transmission of this infection, and monitor outbreaks.
Tuberculosis (TB) disease rates in some parts of London are as high as in Sub-Saharan Africa, and drug-resistant strains are becoming increasingly common. These require specific treatments, and if doctors know that a bug is resistant they can start therapy earlier, often leading to better outcomes.
Whole genome sequencing reveals the complete genetic (DNA) sequence of an Mtb sample, in many cases pinpointing drug resistance mutations so that appropriate treatments can be given. However, this process currently takes weeks because samples need to be grown in the laboratory before there is enough genetic material to measure.
The new method, published in the Journal of Clinical Microbiology, allows scientists to enrich Mtb DNA directly from patient sputum (mucus) samples. This means that the samples can be sequenced and analysed straight away, avoiding the need to spend weeks growing them in the lab.
To extract Mtb from sputum samples, the researchers used probes made of ribonucleic acid (RNA) molecules, engineered to bind to Mtb DNA. The method was tested on 34 routine samples taken from patients in London and Lithuania, where resistant Mtb strains are a significant problem. The sequencing results from sputum matched perfectly with those from the relevant cultured isolates.
The technique has also been applied to other infections including chlamydia, HIV, hepatitis, herpes, influenza A, norovirus and cytomegalovirus. Although a lot of infections can be treated with antimicrobials, resistance is a growing problem globally. Diagnostic techniques that enable more precise treatments to be given earlier could help to combat drug resistance in a wide range of infections, not just TB.
The team hope to further refine the technique in future, to make it cheaper and simpler so that it could be used in countries with less economically-rich healthcare systems where drug-resistant TB is common.
Based on material originally posted by University College London.
(Image: Mycobacterium Tuberculosis, source)