In an editorial accompanying the study, Johns Hopkins infectious disease specialists Richard Chaisson, M.D., and Eric Nuermberger, M.D., call the proliferation of the drug-resistant organisms an "enormous challenge" to eradicating TB, which now kills 1.5 million people each year, mostly in the developing world.
More worrisome among the study findings, says Chaisson, a professor at the Johns Hopkins University School of Medicine and founding director of its Center for Tuberculosis Research, was that the majority of the estimated 110,000 drug-resistant cases occurred among people newly diagnosed with TB, indicating that these drug-resistant bacteria were transmitted from one person to another.
Only 3 percent of all newly detected cases were tested for drug resistance.
This research, Chaisson
says, "upsets the old dogma" that drug-resistant organisms occur mostly in people who fail to respond to therapy or in infected people who relapse after drug treatment.
In sum, he
says, drug resistance appears to be present in new cases on a large scale, and drug-resistance testing should not be limited to previously treated patients.
says the study also highlights the urgent need for faster testing of those newly diagnosed to determine drug resistance.
Current laboratory testing methods, while relatively cheap (at less than $5 per person), take several weeks to show bacterial growth in sputum samples.
Same-day results are available using high-tech, molecular assays, but they dramatically raise the test cost to as much as $40 per person, a cost he
says is worth it, given the "sobering" scope of the problem.
According to Chaisson
, multidrug resistant strains of TB cannot be effectively treated by either of the two most commonly used antibiotics, isoniazid and rifampin.
and Nuermberger point out that individual drug studies are required by U.S. and global regulatory agencies.