By Cheryl Pellerin
USINFO Staff Writer

Washington - International incidents have focused recent attention on deadly forms of drug-resistant tuberculosis (TB), and the World Health Organization (WHO) and the Stop TB Partnership are launching a two-year plan to help patients and communities most at risk.

The Global MDR-TB and XDR-TB Response Plan 2007-2008 set out measures needed over the next two years to prevent, treat and control extensively drug-resistant TB (XDR-TB) and multidrug-resistant TB (MDR-TB). The plan lays out steps to give access to drugs and diagnostic tests to all MDR- and XDR-TB patients by 2015, potentially saving up to 1.2 million lives.

The Stop TB Partnership, formed in 2000 to eliminate TB as a public health problem, is a network of more than 500 international organizations, countries, public-sector and private donors, and nongovernmental and governmental organizations.

The plan emphasizes an urgent need to boost basic TB control and to target investment in strengthening programs for treating drug-resistant TB, building capacity in diagnostic laboratories, expanding infection control and surveillance, and supporting research in diagnostics, drugs and vaccines.

"The persistence of the TB epidemic underscores the importance of continuing fundamental research," said Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, in a recent statement, "to better understand how [MDR-TB] interacts with the host and to translate these findings into new health care interventions to improve the diagnosis, treatment and prevention of TB infection and disease."

NIAID is the lead agency of the National Institutes of Health for TB research.

DEADLY STRAINS

TB microbes spread from person to person through the air. Globally, nearly 9 million people get TB each year, and 1.6 million die as a result.

One-third of the world population is infected with latent (inactive) TB. The disease usually does not become active unless something reduces a person's immunity - a disease like AIDS, advancing age or some medical conditions.

TB is treated with a six- to nine-month course of "first-line" (most effective) drugs. If patients do not complete the drug course or are not treated properly, they can develop MDR-TB, which is resistant to at least two of the best anti-TB drugs, isoniazid and rifampicin. Those with MDR-TB must be treated with more expensive, less effective second-line drugs for 18 to 24 months.

If they do not complete this course or are treated with the wrong drugs, they can develop XDR-TB, a relatively rare type of MDR-TB that is resistant to first- and second-line drugs. There could be 50,000 cases of XDR-TB worldwide.

INTERNATIONAL INCIDENTS

Worldwide attention focused on XDR-TB in March 2006, when researchers reported on an emerging global threat of highly resistant TB strains.

Six months later, a cluster of virtually untreatable XDR-TB cases arose in an area of South Africa that has a high prevalence of HIV. All but one of 53 patients died within 25 days after samples were taken for drug-resistance tests.

In May, scientists at the U.S. Centers for Disease Control and Prevention (CDC) diagnosed an international air traveler from the United States with XDR-TB. (See related article.)

After Andrew Speaker - a 31-year-old lawyer from Atlanta - returned to the United States and was served with a federal order of isolation, he traveled to the National Jewish Medical and Research Center in Colorado, a leader in treating lung diseases.

There, on July 3, officials from CDC and National Jewish announced that tests from National Jewish and a second test from CDC showed that Speaker actually had MDR-TB.

"There's not a lot of difference between XDR- and MDR-TB in the sense that the public health response is the same," said Dr. Charles Daley, head of the Infectious Disease Division at National Jewish, during a July 3 press briefing.

"It makes a big difference to me, as a clinician, however," he added, "because I can pick another couple of drugs up and add them to the treatment regimen and improve the chance of cure."

Even though CDC and National Jewish are both TB reference laboratories (regional or national resources with specific technical capabilities), and CDC is an international reference lab, CDC officials are not yet sure why their initial lab results indicated XDR-TB.

"Any time there is a concern or conflict with a test result," said Dr. Mitchell Cohen, director of CDC's Coordinating Center for Infectious Diseases, "we automatically review those results and see whether there are clear explanations as for the differences."

A significant problem, Cohen added, is "not having the types of diagnostic tests we truly need to be able to address the challenge from TB. Different or discordant test results in different laboratories are an important issue. If we could, working together, develop a gold-standard test that could give us a definite answer, that would be a tremendous step in the right direction."

TB test results of passengers and crew who traveled on the trans-Atlantic flights with Speaker will be completed over the next few weeks.

Additional information about MDR- and XDR-TB is available on the CDC Web site.

More information about TB and the Global MDR-TB and XDR-TB Response Plan 2007-2008 is available on the WHO Web site.

For additional information about U.S. and international efforts to combat TB, see Health.