Hardest-to-treat form of TB rare in U.S. -study

• Infections • Nov 13, 08

The hardest-to-treat form of drug-resistant tuberculosis is a growing threat in many parts of the world, but remains quite rare in the United States, U.S. government health researchers said on Tuesday.

From 1993 through 2007, there were 83 cases of extensively drug-resistant TB, or XDR-TB, reported in the United States, U.S. Centers for Disease Control and Prevention researchers wrote in the Journal of the American Medical Association.

XDR-TB defies nearly all drugs used to treat tuberculosis, the top cause of infectious disease death among adults worldwide. It is more difficult to treat than the more common multidrug resistant TB, or MDR-TB, which does not respond to the treatment by two or more of the primary drugs used for TB.

Last year, there were two cases of XDR-TB reported in the United States, the researchers said. There were 18 XDR-TB cases detected in 1993 but no more than nine in any year since.

Thirty-five percent of the people with XDR-TB died during treatment. The death rate for XDR-TB was nearly double the rate among MDR-TB cases and more than six times greater than among people with TB that responds to typical drug treatment.

Tuberculosis is an infectious bacterial disease typically attacking the lungs. The emergence and spread of drug-resistant germs makes treating it much harder and more expensive and makes the disease more likely to kill.

Among people with XDR-TB with HIV test results, 53 percent were HIV-positive, the researchers said. Of the XDR-TB cases, 45 percent were foreign born and 40 percent were Hispanic.

CDC epidemiologist Dr. Peter Cegielski, who led the most comprehensive study ever conducted of drug-resistant TB in the United States, warned against complacency.

“As long as there is XDR TB anywhere in the world, there is a risk in the United States, and we have to address the threat. TB doesn’t respect international borders. The TB germs don’t carry passports,” Cegielski said in a telephone interview.

There were 212,896 TB cases from 1993 through 2007, of which 3,379 were classified as MDR-TB and 83 as XDR-TB.

Tuberculosis in the United States was in the spotlight in 2007 when Atlanta lawyer Andrew Speaker triggered an international health scare by flying to and from Europe for his wedding and honeymoon with a drug-resistant form of TB.

He initially was thought to have XDR-TB but it was later determined to be lesser MDR-TB. He was successfully treated.

Globally, cases of drug-resistant tuberculosis are being recorded at the highest rates ever seen, according to the World Health Organization. They account for 5 percent of the 9 million new TB cases annually and are a particular threat in Russia and other former Soviet republics, India, China and South Africa.

The WHO said about 489,000 MDR-TB cases emerged worldwide in 2006, of which about 40,000 were XDR-TB.

By Will Dunham
WASHINGTON (Reuters)