Tuberculosis even more drug resistant.

• Author: Stair, Peter
• Position: United States. Centers for Disease Control and Prevention

According to a recent survey by the World Health Organization and the U.S. Centers for Disease Control and Prevention, nearly 1 in 30 human cases of tuberculosis (TB) is now resistant to both primary and secondary antibiotic treatments. The results were published in the March 24 issue of the Centers' Morbidity and Mortality Weekly Report.

The survey reports that the prevalence of "multiple-drug resistant" TB strains, which can survive the first two antibiotics typically used (isoniazid and rifampin), rose from 29 percent to 39 percent between 2000 and 2004. The proportion of strains additionally resistant to three or more or the six classes of second-line drugs increased from 5 percent to 7 percent. This was the first international appraisal of these so-called "extensively-drug-resistant" varieties.

TB, a bacterium that can fatally infect the lungs, was long a leading cause of human death, killing 50 percent of those sickened. The use of streptomycin and other antibiotics starting in the 1940s made the disease highly treatable, but misuse of these drugs in recent decades has allowed resistant strains to flourish.

While a proper treatment regimen extends for six months or more, TB patients are often inclined to curtail this after only a few weeks, once their symptoms disappear. In many poor countries, frail medical systems also prevent access to adequate or regular drug supplies. Such conditions are ideal for encouraging the evolution of resistant strains; since the 1960s, it has become standard for patients to receive two or three antibiotics in tandem to combat the rising ineffectiveness of some drugs.

In the 1990s, strains resistant to even...