Drug Resistance in Tuberculosis

Abstract

Tuberculosis (TB) kills about 2 million adults and around 100 000 children every year. One-third of the worlds population are currently infected with Mycobacterium tuberculosis and many have active disease. In Europe TB emerged as a major disease in the latter part of the 14th century. The industrial revolution saw rapid growth of urban centres where overcrowding with poor living conditions provided ideal circumstances for the spread of the disease. Great impact was made by streptomycin and isoniazid so that by the 1970s TB was no longer being considered a problem in the developed world. But beginning in the 1980s the number of new cases of TB in USA and across Europe rose sharply. The pattern was repeated in many countries and worldwide throughout the 1990s and into the new millennium. The incidence of TB climbed to over 9 million cases every year. In 1993 the World Health Organization (WHO) declared TB as a global emergency. During the 1990s multidrug resistant tuberculosis (MDR-TB) defined as resistance to at least isoniazid and rifampicin emerged as a threat to TB control. MDR-TB requires the use of second line drugs that are less effective more toxic and costlier. In a global survey of 17 690 TB isolates during 2000-04 20% were MDR and 2% were extremely drug resistant (XDR). XDR-TB is defined as MDR plus resistance to any fluoroquinolones and at least one of three injectable second line drugs kanamycin and amikacin or capreomycin or both. Currently one in ten new infections is resistant to at least one antituberculosis drug. (excerpt)