TB strain identified as 'virtually untreatable'

By Wai Lang Chu

- Last updated on GMT

Related tags Tb Tuberculosis

The World Health Organisation (WHO) has revealed details of a
'super strain' of tuberculosis, which is not only resistant to
first choice treatment drugs, but also three or more of the six
classes of second-line drugs.

The news is a worrying development as the emergence of strains that are resistant to the multitude of drugs has gained significant momentum. TB presently causes about 1.7m deaths a year worldwide.

The WHO also recognised the threat of TB amongst people living with HIV/AIDS. Treating the two diseases at the same time is difficult because of negative interactions between some ARVs used to treat HIV/AIDS and TB drugs.

Resistance to anti-TB drugs in populations is a phenomenon that occurs primarily due to poorly managed TB care. Problems include incorrect drug prescribing practices by providers, poor quality drugs or erratic supply of drugs, and also patient non-adherence.

MDR-TB (Multidrug Resistant TB) describes strains of tuberculosis that are resistant to at least the two main first-line TB drugs - isoniazid and rifampicin. XDR-TB, or Extensive Drug Resistant TB (also referred to as Extreme Drug Resistance) is MDR-TB that is also resistant to three or more of the six classes of second-line drugs.

Globally, the WHO estimates there are about 425,000 cases of MDR TB a year, mostly occurring in the former Soviet Union, China and India.

Recent findings from a survey conducted by WHO and CDC on data from 2000-2004 found that XDR-TB has been identified in all regions of the world but is most frequent in the countries of the former Soviet Union and in Asia.

In the United States, the WHO said that 4 per cent of MDR-TB cases met the criteria for XDR-TB.

In Latvia, a country with one of the highest rates of MDR-TB, 19 per cent of MDR-TB cases met the XDR-TB criteria.

Separate data on a recent outbreak of XDR-TB in an HIV-positive population in Kwazulu-Natal in South Africa was characterised by alarmingly high mortality rates.

Of the 544 patients studied, 221 had MDR-TB. Of the 221 MDR-TB cases, 53 were defined as XDR-TB. Of the 53 patients, 44 had been tested for HIV and all were HIV-positive.

52 of 53 patients died, on average, within 25 days including those benefiting from antiretroviral drugs.

Drug resistance data available from Africa has indicated that while population prevalence of drug resistant TB appears to be low compared to Eastern Europe and Asia, drug resistance in the region is on the rise.

The WHO stated that given the underlying HIV epidemic, drug-resistant TB could have a severe impact on mortality in Africa and requires urgent preventative action.

Paul Sommerfeld of TB Alert, said: "XDR TB is very serious - we are potentially getting close to a bacteria that we have no tools and no weapons against."

"What this means for the people in southern Africa, who are now becoming susceptible to this where it is appearing, is a likely death sentence. For the world as a whole it is potentially extremely worrying that this kind of resistance is appearing. This is something that I am sure the WHO will be taking very seriously."

Last week, the WHO joined other TB experts at a two-day meeting in South Africa (7-8 September) to assess the response required to critically address TB drug resistance, particularly in Africa.

Related topics Preclinical Research

Related news

Show more

Follow us


View more