5 September 2006

“XDR-TB” (Extensive (Extreme) Drug Resistant-Tuberculosis): WHO describes as “Virtually Untreatable”

On September 5^th the World Health Organization (WHO) posted on their website an article titled “Emergence of XDR-TB”. This form of “extensive (or “extreme”) drug resistant tuberculosis” is “virtually untreatable” and may be associated with a very high mortality (e.g., 52/53 patients with XDR-TB died in a recent study of HIV-positive patients from Kwazulu-Natal, South Africa. The brief summary from the WHO and news of a conference in South Africa this September 7-8, supported by WHO and CDC, can be found online at: www.who.int/mediacentre/news/notes/2006/np23/en/index.html

XDR-TB is defined by WHO as Multidrug–Resistant TB (MDR-TB) “that is also resistant to three or more of the six classes of second line drugs” against TB. MDR-TB is defined as strains of TB that are resistant to at least the two main first-line TB drugs isoniazid and rifampicin. WHO guidelines for “programmatic Management of Drug-Resistant Tuberculosis” are provided in a 186-page document, with four Editor-in-Chiefs, on the WHO website at: www.who.int/tb/dots/dotsplus/en/index.html

Who reports that XDR-TB was first described earlier this year after a WHO-US CDC survey that found this TB strain in all parts of the world. For example, it was most frequent in nations of the former Soviet Union, such as Latvia (19% of MDR-TB cases are also XDR-TB), and Asia. In the USA 4% of MDR-TB patients also had XDR-TB.

A potential link with HIV is noted in the WHO document and also in a September 5^th entry on ProMed mail. As noted by the ProMed commentator (LM) today, the development of XDR-TB, and its apparent very high mortality rate, as cited in the study from South Africa, is likely to be multifactorial.

WHO cites potential contributing factors in TB drug-resistance as “incorrect drug prescribing practices by providers, poor quality drugs, or erratic supply of drugs, and also patient non-adherance”. WHO goes on to state that “Given the underlying HIV epidemic, drug-resistant TB could have a severe impact on mortality in Africa and requires urgent preventative action”.

All in all, this is bad news in the long global war against tuberculosis and the ongoing human pandemic of HIV/AIDS.

Daniel R. Lucey, MD, MPH

Director, Center for Biologic Counterterrorism and Emerging Diseases

EROne Institutes, Washington Hospital Center

Adjunct Professor of Microbiology and Immunology

Georgetown University Medical Center, Washington, DC

Website: www.BePast.org email:Daniel.R.Lucey@Medstar.net