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Drug-resistant TB set to become more dominant

Multidrug-resistant forms of TB could become dominant strains

OnMedica staff

Wednesday, 19 May 2010

Almost half a million cases of multidrug-resistant tuberculosis (MDR TB) occurred worldwide in 2008, but most remained untreated, states a report in The Lancet.

Several papers in special issue of the journal examine the international problem of TB, and drug resistance. Authors say they estimate that almost 1 in 25 (3.6%) of the 440,000 TB cases in 2008 were multi-drug resistant, but only 7% of these were identified and treated.

They warn that extensively drug-resistant TB (XDR TB), which is even more difficult to treat, has also been reported in most countries. It is now known that transmission of resistant strains can occur from infected people to those with no prior exposure to TB drugs.

Unless there is significant investment in technology and capacity for prevention, diagnosis and treatment, MDR TB threatens to become the dominant strain of TB over the next few decades, predict the researchers.

Current programmes to control TB are threatened by the drug-resistant strains, which have lower cure and higher mortality rates. In addition, drug treatment costs about 175 times as much and takes four times as long for resistant strains. However, where rates of HIV co-infection are low, effective treatment programmes can have success rates as high as 83% for MDR TB and 60% for XDR TB.

New diagnostic tests and drugs might become available during the next decade and would help control of MDR and XDR TB. The authors argue that they must be made available in resource-limited settings that are hit hardest by this epidemic, but we must “ensure that these new drugs are not exposed to the weak health systems and irrational drug practices that are currently giving rise to resistance.”

They conclude: “Unless countries invest substantially in management of MDR TB, the possibility remains that MDR strains could become the dominant form of TB. Moreover, the future possibility of strains that are totally resistant to all anti-tuberculosis drugs is not inconceivable.

“Equally important, especially in the highest-burden countries of India, China, and Russia, will be a commitment to tuberculosis control including improvements in national policies and health systems that remove financial barriers to treatment, encourage rational drug use, and create the settings necessary to manage MDR TB on a national scale.”

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