XDR-TB: Extremely Drug Resistant, Extremely Scary

Tuberculosis has likely plagued humanity since the origin of our species. In 460 B.C., Hippocrates identified Phthisis (Greek for wasting) as a fatal disease that was most prevalent in the population at that time. Throughout human history, tuberculosis has killed millions, more than any other pathogenic organism. Tuberculosis flourishes wherever poor living conditions exist - poor ventilation, crowding as in densely populated urban areas and prisons. During the Industrial Revolution, tuberculosis decimated the urban poor and in 19th century England, it was the cause of one in four deaths. The unknown and the famous: poet John Keats, Frederick Chopin, Dr. Anton Checkov, George Orwell, Emily Bronte, Robert Louis Stevenson were all victims of the disease. Dr. Robert Koch stunned audiences in 1882, identifying Mycobacterium tuberculosis (Mtb) as the bacterium causing TB. He won a Nobel Prize in Physiology or Medicine in 1905 for his discoveries about TB. A vaccine was developed in 1908, but by the 1940's, antibiotics like streptomycin were the drug of choice. The big three; isoniazid, rifampin and ethambutol were soon introduced and by the 1960's, it seemed the epidemic was controlled.

Today, one hundred and twenty five years after Dr. Koch identified the organism, public health officials believe that one third of humans, or 2 billion people, are infected with TB. 1.6 million people died of TB each year in 2004 and 2005 and 85% of the victims resided in Africa and Asia. Of the 1.6 million who died of TB, 195,00 were co-infected with HIV. Public health officials describe a "deadly synergy" between HIV/AIDS and TB which has contributed to the spread of the disease and resistance to drug treatment. TB is now the leading cause of death for people with HIV/AIDS. The ICRC (International Red Cross) reports that TB is 100 times more prevalent in prisons than in the general public, and prisons in Central Asia, Africa and the Caucasus are seeing an increase in drug-resistant cases. TB is an airborne illness that is treatable, but if not diagnosed early, it can mutate into drug-resistant strains. Africa's large AIDS population has been hit by a virulent strain: XDR-TB. This strain is now found in the US and Canada, in all 35 countries world-wide. What is frightening about the outbreaks is that they are not transmitted person to person but seem to be a progression of mutation independent of geographic barriers.

MDR-TB (Multi-drug Resistant TB) is a strain of the disease that is resistant to isoniazid and rifampicin. XDR-TB is resistant to 3 or more of the 6 classes of second line drugs. XDR-TB was first found in South Africa in the HIV/AIDS population. It is thought that resistance to drugs is the result of poorly managed care--incorrect prescribing practices, non-compliance with prescription therapy, and poor quality drugs with erratic supply. When people are given enough medication to allay symptoms but not kill the organism, the organism mutates to resist the drug. Additionally, there are significant problems with drug interactions between anti-tuberculosis and anti-HIV medications that may make compliance difficult for patients. There is no known cure.

Clinicians may want to participate in the on-line eForum, One-in-Ten Campaign.
The Tuberculosis Coalition for Technical Assistance (TBCTA), a partnership of WHO, CDC, USAID and others has published an on-line resource: International Standards for Tuberculosis Care.

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