Health officials said Thursday they are seeing what appears to be a disturbing increase around the world in tuberculosis infections resistant to both the first- and second-line antibiotics used against TB.
"It's basically a death sentence. If people are failing first- and second-line drugs and we don't have in the pipeline a new drug for immediate use, that's a crisis," said Dr. Marcos Espinale, executive secretary of the World Health Organization's Stop TB Partnership.
The CDC and WHO surveyed a network of 25 tuberculosis laboratories on six continents from 2000 to 2004 and found that one in 50 TB cases around the world is resistant not only to the usual first-choice TB treatments, but also to many medications that represent the second line of defense.
The survey represents the first international data on what is being called "extensively drug-resistant" TB.
But the survey also found many cases of a more difficult form of TB — one that does not respond to at least three of six classes of second-line drugs. That is especially worrisome, because second-line drugs are generally considered more toxic and less effective.
"These are individuals who are virtually untreatable with available drugs," said Dr. Kenneth Castro of the CDC.
The survey looked at 17,690 TB cases that were analyzed for drug susceptibility. Of those, 20 percent were multidrug-resistant and 2 percent were extensively drug-resistant.
The problem was worst in Latvia, where public health care deteriorated after the Soviet Union collapsed. Doctors believe TB develops resistance to drugs because some patients fail to complete a full course of medication.
In the United States, health officials looked at 169,654 TB cases from 1993 to 2004 that were analyzed for their drug response and found that 1.6 percent were multidrug-resistant and 0.04 percent extensively drug-resistant.
U.S. multidrug-resistant cases rose from 2003 to 2004, from 113 to 128. Though the number was small, it represented the largest single-year increase in more than 10 years. Ninety-seven of those 128 cases were in people born in other countries, mostly Mexico, the Philippines and Vietnam.
Overall, the TB rate in the United States has never been lower. In 2005, about 14,100 cases were reported, or 4.8 cases per 100,000 people. That is a 4 percent decline in the rate from 2004. However, the TB rate in foreign-born people in the United States was 8.7 times that of U.S. natives.
"Worsening resistance around the world poses a problem in the U.S.," Castro said.
Dr. Henry Blumberg, an Emory University medical school professor, said the figures are preliminary and the problem may be bigger than the numbers indicate.
Some drugs under development might become effective treatments for these difficult forms of TB. But CDC funding for TB control and research has not kept up with inflation in the past decade, Blumberg said.
