CDC finds 'worrying' rise in 'virtually untreatable' TB

Study links drug resistance to availability of second-line treatment.

CDC researchers recently found that nearly half of tuberculosis (TB) patients in eight countries are resistant to at least one second-line drug, a "worrying" finding that they say may signal the emergence of "virtually untreatable" TB.

In a study published last week in The Lancet, CDC researchers examined 1,278 TB cases in Estonia, Latvia, Peru, the Philippines, Russia, South Africa, South Korea, and Thailand. They found that:

  • 43.7% of TB cases were resistant to at least one second-line drug; and
  • 6.7% of TB cases were "extensively drug-resistant," meaning resistant to first-line drugs and at least two second-line treatments in different classes.

"The global emergence of extensively drug-resistant tuberculosis heralds the advent of widespread, virtually untreatable tuberculosis," the study says.

The researchers found a correlation between the prevalence of drug resistance and the availability of second-line treatments. For example:

  • In Thailand, where second-line drugs were introduced in the last decade, 33% of TB cases showed second-line drug resistance; and
  • In South Korea and Russia, where second-line drugs have been available for more than 20 years, over 60% of TB patients showed second-line drug resistance.

"As more individuals are diagnosed with, and treated for, drug-resistant TB, more resistance to second-line drugs is expected to emerge," says Tracy Dalton, lead author of the study (Kelland, Reuters, 8/30; Kitamura/Narayan, Bloomberg, 8/30; Gever, MedPage Today, 8/30).

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