XDR-TB strain of tuberculosis sparks alert

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Virulent new strain of tuberculosis sparks alert

By M.A.J. McKenna in Atlanta, Georgia March 25, 2006

A STRAIN of tuberculosis that resists almost all of the drugs used to

fight it is appearing around the world, including the US, the World

Health Organisation and the Centres for Disease Control and

Prevention have warned.

The strain, known as " extensively drug-resistant tuberculosis " , or

XDR-TB, has the potential to return TB treatment " to the pre-

antibiotic era " in which the only treatment was cutting out parts of

the lungs.

" XDR-TB is cause for concern because it is widely distributed and

renders patients virtually untreatable, " said Castro,

director of the division of TB elimination at the Centres for Disease

Control. If the strain went unchecked, he added, deaths from TB -

which affects 9 million people annually and kills 2 million - would

rise.

TB is also the biggest killer of people with HIV, causing about 13

per cent of AIDS deaths.

But while cases of the debilitating and potentially fatal disease are

subsiding in the US, the subset of infections resistant to some or

most of the drugs used against TB is burgeoning, the WHO said.

Between 2000 and 2004, 20 per cent of bacteria recovered from TB

patients and tested at WHO-affiliated labs worldwide were resistant

to the two main drugs, isoniazid and rifampin, used to treat the

disease, earning them the label " multi-drug resistant " .

Health authorities fear the development of drug resistance in

tuberculosis because it transforms treatment of the disease from a

six-month course of daily doses of the two main drugs into a regimen

that stretches up to two years.

The regime uses a menu of six " second-line " drugs that are less

effective, more expensive and more toxic to patients - the drugs can

fail and lead to the death of patients.

Because TB-control programs around the world were complaining of

patients who did not recover even with those lengthy treatment

programs, the WHO undertook a second analysis to determine how

resistant TB had become, said Marcos Espinal of the WHO's Stop TB

Partnership.

When they rechecked their samples, the labs found that extensively

drug-resistant TB - defined as a TB strain that resists not only the

two main drugs, but at least half of the secondary drugs - had

existed at least since 2000 and had been growing.

Overall, the WHO said, 347 cases of extensively drug-resistant TB had

been found since 2000. By 2004 this had risen to 11 per cent of all

drug-resistant cases in industrialised countries.

With 500,000 people worldwide suffering from multi-drug-resistant TB,

the true rate of the extensively resistant form is likely to be

higher than the labs have recorded, because many countries do not

have the resources for TB surveillance and analysis, Dr Espinal said.

The study noted that while the most-resistant TB was identified in

all regions, it was most common in Eastern Europe and western Asia.

Factors contributing to increases in drug resistance include

interruption in treatment among TB-infected people, lack of testing

and the absence of infection-control measures in large settings such

as hospitals and prisons, researchers said.

An analysis done just in the US found 74 cases of XDR-TB between

1993, when the Centres for Disease Control began recording any case

of drug resistance, and 2004.

http://www.smh.com.au/articles/2006/03/24/1143083994124.html