Dr Sarah Dunstan, a senior research fellow at Peter Doherty Institute for Infection and Immunity, Melbourne, Australia, is the co-author of a first-of-its-kind study on tuberculosis, where the scientists identified the most virulent strain of tuberculosis-causing bacteria in Asia.  The findings could be a key to developing more effective diagnostic tools and drugs.

Dr Dunstan talks to Gunjan Sharma about the study, and how it is going to help develop new strategies to diagnose, treat and protect against emerging and evolving strains of the bacteria.
 
Tell us more about the study about Beijing strain?

We studied tuberculosis-causing (TB) bacteria in Ho Chi Minh City, Vietnam. For our study, we isolated TB bacteria from 1635 patients suffering from tuberculosis and sequenced the DNA of these isolated bacteria. We found that in 60 per cent of patients, the disease was caused by bacteria belonging to one lineage-- the Beijing strain.

The Beijing strain is the most commonly found strain in Asia, including India. In Ho Chi Minh City, we showed that Beijing strain spreads more readily from person to person.
The findings, published in Nature Genetics, concluded that the strain of TB-causing bacteria known as the Beijing strain was responsible for 59 per cent of infections. Another interesting observation was 75 per cent of these patients are young. 
 
How will this research help?

TB is the leading cause of death from a single infectious agent globally. Mycobacterium tuberculosis typically affects the lungs, but can also infect other sites of the body.  Multiple antibiotics are used to treat TB. The treatment is long (six months or more) and the emergence of drug-resistant bacteria is a threat to global health.

As the current vaccine against TB has limited effectiveness, it is important to develop new treatments and vaccines.  Understanding more about the diversity of the bacteria, and that some strains spread more readily than others, can help scientists develop new tools to fight TB. This information can also help form strategies to prevent its spread. Besides, we can trace all the people a patient with Beijing strain has come into contact with. Early screening and early treatment is the best way to control TB spread.

But is your research limited to Beijing strain?

Currently, we are focusing on studying the mutations in the Beijing strain that may be making it more virulent.  We are also looking at drug resistance mutations in all the different TB strains collected from our study in Vietnam. 

How is genomics changing the tuberculosis treatment?

Genomics gives us an insight into the bacteria and host relationship. This information can help scientists develop new drugs and treatment regimens, new vaccines, and new rapid diagnostic tools.

Current diagnostic tools take 5-6 weeks to confirm a drug-resistant infection and till then we have no choice but to put the patients on medications for drug-sensitive TB. Ineffective treatment prolongs patient suffering and can cause further spread of drug-resistant-TB.

I am looking forward to a day when we could identify a drug-resistant-TB within a day so that we can give appropriate treatment to the patient immediately. Genomics is the technology that can make this a reality.
 
What do you think is the most important factor contributing to the rise in drug-resistant-TB?

There are two reasons. Firstly, diagnosing patients with drug-resistant TB patients quickly, and getting them onto effective treatment early, will stop the spread of drug-resistant bacteria. Secondly, as TB treatment is so long, and the treatment can have many side-effects, it is difficult for patients to comply with the treatment, which puts them at high risk of developing and spreading drug-resistant TB.

We urgently need to develop new rapid diagnostic tests for drug-resistant TB, and develop shorter courses of treatment to help people comply.