Growing presence of drug-resistant tuberculosis fuels need for faster development of new combination therapies

Growing presence of drug-resistant tuberculosis fuels need for faster development of new combination therapiesJune 6, 2012 in Diseases, Conditions, SyndromesJohns Hopkins experts in the prevention and treatment of multidrug-resistant tuberculosis are calling for increased screening and more rapid testing of the 9 million people worldwide estimated to be infected each year with TB and now at risk for this form of the highly contagious lung disease.The call follows results of a survey showing that the harder-to-treat TB variants are much more widespread than previously thought. Details of the survey, to be published in The New England Journal of Medicine online June 7, provide the first-ever, nationwide estimate of the size of the problem in China, where over a million new infections occur each year. The 2007 survey of more than 4,000 Chinese newly diagnosed or recently treated for TB showed that one in 10 was infected with drug-resistant strains of TB, more formally known as Mycobacterium tuberculosis. Among this group, some 0.5 percent (or more than 5,000, annually) were diagnosed with extensively drug- resistant TB, which the experts say is nearly incurable. TB is spread when uninfected people inhale small numbers of TB bacteria coughed up and spewed into the air by people already infected. Antibiotics can cure the disease, but compliance with the lengthy course of treatment is uncertain and the drugs available in the developing world to treat the disease are limited to fewer than a dozen, mostly older medications. 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.