Major step forward in treatment of TB

Scientists hope the discovery will also pave the way to new vaccines and treatments, and help to combat tuberculosis around the world.

Only about one in 10 people infected with tuberculosis go on to develop an "active" disease and suffer symptoms.

While they are "latent" non-symptomatic carriers, they cannot transmit tuberculosis bacteria to others.

Currently, a skin or blood test can show if someone is latently infected with the tuberculosis bug Mycobacterium tuberculosis (MTb), but there is no way of identifying who is likely to develop full-blown tuberculosis during their lifetime and become contagious.

This could now change after British and United States researchers found a genetic signature in the blood of "active" tuberculosis patients that appears to make them susceptible to the disease.

The same DNA fingerprint was seen in the blood of around 10 per cent of patients with "latent" infections, marking them out as candidates for full-blown disease.

Knowing which patients are at risk of developing "active" tuberculosis would allow doctors to administer early and more effective treatment, and thus reduce the number of infectious cases.

The findings were reported yesterday in the journal Nature.

Tests to uncover the genetic signature were initially conducted in London, where more than 3,500 tuberculosis cases were diagnosed last year – 40 per cent of the UK total.

A comparative analysis was carried out in Cape Town, South Africa, to confirm the findings were representative in different parts of the world.

More than 400 patients took part in the study.