TB, the infectious lung disease, is a leading cause of death from infectious diseases worldwide, second only to HIV/AIDS.
The airborne disease that we all thought had been eliminated by the 1960s, is now killing nearly 2 million people worldwide every year. According to the World Health Organization (WHO), new infections of tuberculosis, or TB, occur at the rate of one per second.
And also of increasing concern to health professionals and organizations worldwide is the sharp rise in drug-resistant strains of TB.
Of these, extremely drug-resistant tuberculosis, XDR-TB, has emerged as a top priority – in Sub-Saharan Africa it is said to be threatening to undermine the progress in the fight against HIV/AIDS. The WHO, the Bill Gates Foundation and the European Union have launched programmes to tackle the problem.
Poorer countries are not the only ones to be hit by TB. London for example is called “the TB capital of Europe”, and most large cities in Europe and North American have seen sharp rises in the disease.
But the problem is bigger in Africa and Asia because of the higher prevalence of HIV/AIDS and reduced healthcare capability, particularly shortages of TB drugs and ensuring patients finish the treatment programme which can take up to 18 months. This is how resistant strains emerge.
Other groups have also launched campaigns. In the US, philanthropist and political activist George Soros, chair of the Open Society Institute announced earlier this week a coalition with Partners in Health, Brigham and Women’s Hospital, and the RESULTS Educational Fund. They have set up a fund to develop new treatments for patients with drug-resistant TB and HIV/AIDS in developing countries.
The coalition have called on governments in the wealthier nations to support initiatives to stop the global epidemic that hits poorer nations with under-resourced healthcare systems much harder. Basic control of TB is the key, they say.
Many health experts are saying that the way to stop the dual epidemic is to fight it on two fronts. Strengthen basic control of TB, and develop new treatments for the drug-resistant strains.
A potential new treatment was highlighted earlier this month when UK scientists announced that a drug used to treat common fungal infections could hold the key to treating drug-resistant TB.
Biologists at The University of Manchester showed that compounds known as azoles – the active agent in many antifungal drugs – kill the TB bacteria, and could also be effective against emerging drug-resistant strains.
Professor Andrew Munro, who led the research in Manchester’s Faculty of Life Sciences, said “TB is back with a vengeance with a third of the world’s population currently infected”.
Professor Munro explained the resurgence of TB and the drug-resistant strains: “The bacterium survives the initial attack by the body’s immune system and then lies dormant, usually in the lungs, waiting for any sign of weakness, such as a secondary infection. Its resurgence over the last 20 years has been closely associated with the AIDS epidemic, which destroys the human immune system and has allowed TB to get a grip once again.”
“People in places like India or Africa would be given antibiotics but often not in sufficient quantities to kill the bug completely; this is how resistant strains develop and these regions have become huge breeding grounds for these ‘super strains’,” said Professor Munro.
In researching the DNA of the TB bacterium, the Manchester scientists found it had a large number of enzymes called P450s, which is unusual for a small organism like a bacteria. They discovered that existing anti-fungal treatments based on azoles already target P450s, for instance in the treatment for Candida albicans (the causative agent of thrush).
They found that azoles were good at killing TB bacterium as well, by blocking the action of its P450s that are essential for maintaining cell structure. They also bind tightly to some of the TB P450 enzymes and inactivate them.
The research is published in the Journal of Biological Chemistry.
Meanwhile the WHO has announced that 650 million dollars will be needed every year to treat over 1.5 million patients with drug-resistant TB by 2015.
Dr Paul Nunn of the WHO’s Stop TB Department announced the figure to delegates at the opening session of the 14th Conference on Retroviruses and Opportunistic Infections (RCOI) in Los Angeles at the end of last month. He called drug-resistant TB “one of the most urgent issues in the developing world”.
XDR-TB stands for extremely drug-resistant TB, which according to the WHO is MDR-TB (multi drug-resistant TB) plus additional resistance to certain second line drugs. More specifically, XDR-TB is resistant to the fluoroquinolones and resistant to at least one of the injectable drugs,amikacin, kanamycin and capreomycin.
The problem of XDR-TB was first defined in March 2006 by the US Centers for Disease Control and the WHO. 18,000 TB isolates were shown to contain 20 per cent of MDR-TB. These were tested for 2nd line drug resistance. Ten per cent of the MDR isolates were found to be resistant to 3 or more of the 6 second-line drugs.
In order to fight XDR-TB, developing countries need more advanced facilities, particularly on the laboratory side. Dr Nunn said, for example, there is an acute shortage of laboratories with capability to perform drug susceptibility tests (DST), particularly for second line drugs, which is technically more demanding. “South Africa, alone, has more DST capable laboratories than the rest of sub-Saharan Africa put together,” he said.
According to Dr Paul Farmer, co-founder of Partners In Health and based at Harvard University and Brigham and Women’s Hospital in Boston, the growth of “XDR-TB highlights a global failure to prevent and treat basic TB”. He said TB can be treated with simple and inexpensive drug treatment programme, but when we don’t handle that very well, TB becomes drug resistant.
According to the WHO, the best way to prevent strains of XDR-TB from developing, is to strenghten the control of basic TB. To do this it estimates 5 billion dollars will be needed in 2007 to treat more than 9 million new cases worldwide.
Saturday 24th March is World TB Day.
Click here for World TB Day 2007.
Click here for One in Ten Campaign to stop drug-resistant TB.
Click here for The University of Manchester, UK.
Written by: Catharine Paddock
Writer: Medical News Today