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Drug-resistant strains threatening efforts to eradicate TB, scientists say

Decades of progress in combating tuberculosis are in danger of being derailed by the rising tide of drug-resistant TB strains, experts have warned.

Across the world, resistant TB is on the march. Roughly one in five global cases of the disease is now resistant to at least one major anti-TB drug, a new study points out.

In 2015 there were an estimated 480,000 cases of multi-drug resistant (MDR) TB, said researchers. About half of these were reported in India - where TB was present on an "epic scale" - China and Russia.

However, migration and travel was sewing the seeds of resistant TB in almost every part of the world.

An estimated 5% of all TB cases were classified as MDR, meaning the bacteria cannot be treated with two essential first-line drugs, or even more dangerous XDR (extensively drug-resistant).

Each year, TB kills more people than any other infectious disease, including HIV/Aids, and in 2015 claimed an estimated 1.8 million lives.

Six countries account for 60% of the total number of TB cases worldwide: India, Indonesia, China, Nigeria, Pakistan and South Africa.

Professor Keertan Dheda, from the University of Cape Town, South Africa, lead author of the report published in The Lancet Respiratory Medicine journal to coincide with World TB Day on March 24, said: "Resistance to anti-tuberculosis drugs is a global problem that threatens to derail efforts to eradicate the disease.

"Even when the drugs work, TB is difficult to cure and requires months of treatment with a cocktail of drugs. When resistance occurs the treatment can take years and the drugs used have unpleasant and sometimes serious side effects. Cure rates for drug-resistant TB are poor and people can remain infectious and at risk of spreading the disease."

Prof Dheda heads a commission of international experts who have set out strategy priorities for combating TB over the next 10 years and guidelines for doctors treating resistant forms of the disease.

They are calling for accurate diagnostic tests to deliver individually targeted treatments, clear prescription guidelines, and improved control measures to prevent infection spread.

TB is caused by the bug Mycobacterium tuberculosis and treated with a combination of antibiotics.

Also known as consumption, or "white plague", the infection has ravaged human communities around the world for thousands of years.

Throughout the 18th and 19th centuries, TB raged through Europe killing millions. In England and Wales alone, four million people died from tuberculosis between 1851 and 1910, and many of the victims were in their 20s or younger.

Treatment of TB was revolutionised in the 1950s with the introduction of three antibiotics - streptomycin, isoniazid and para-aminosalicylic acid.

But overuse of antibiotics worldwide has opened the door to newly emerging drug-resistant TB strains with genetic mutations that make them difficult or impossible to treat.

Speaking about the situation in his home country, report co-author Dr Zarir Udwadia, from Hinduja Hospital in Mumbai, India, said: "TB exists on an epic scale in India, and cases of multi-drug resistant TB are an increasing concern.

"Despite some small-scale programmes for compassionate use of new life-saving drugs... there is no widespread access in India meaning these drugs remain unavailable to patients who need them most."

US expert Dr David Dowdy, from Johns Hopkins Bloomberg School of Public Health, said the global TB epidemic was "at a crossroads".

In a commentary accompanying the research, he wrote: " Over the next decade, it is quite possible that we will see a drug-resistant tuberculosis epidemic of unprecedented global scale. But it is also possible that the next decade could witness an unprecedented reversal of the global drug-resistant tuberculosis burden.

"The difference between these two outcomes lies less with the pathogen and more with us as a global tuberculosis control community and whether we have the political will to prioritise a specific response to the disease."

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