MDR / XDR - TB : where do we stand ?

Tuberculosis (TB) is one of the leading causes of death due to an infectious disease, second only to HIV/AIDS worldwide. It is estimated that approximately one third of the world’s population is infected with Mycobacterium tuberculosis, and 10% of infected individuals will develop active TB at some point in their lives. MDR-TB or multidrugresistant tuberculosis is a specific form of drug resistant TB that occurs when bacteria are resistant to at least isoniazid and rifampicin, the two most powerful anti-TB drugs. While XDR-TB or extensively drugresistant tuberculosis is a MDR-TB that is also resistant to any fluoroquinolone and at least one of three injectable second-line anti-TB drugs (capreomycin, kanamycin and amikacin). The concept and term XDR-TB as a distinct nosological entity were first developed by the Centers for Disease Control and Prevention (CDC) in March 2005 and were introduced into public use in October 2005 at the 36 World Conference on Lung Health in Paris, France. For some years, isolated cases of very highly resistant TB have been seen around the world that we would today call XDR-TB. In 2008, an estimated 500,000 individuals throughout the world developed MDRTB with 150,000 deaths. According to World Health Organization (WHO), XDR-TB cases have been detected from at least 58 countries as of March 2010 and 5.4% of MDR-TB cases have XDR-TB with 25,000 new cases of XDR-TB emerging every year. However, the true global prevalence of XDR TB and MDR TB is unknown, because drug susceptibility testing, even for first line drugs, is not routinely performed in most TB endemic countries, and many cases likely are undetected. Incidentally, India and China cover the 50% of world’s burden of MDR-TB and Bangladesh ranks 9 in the list of 25 high priority MDR/XDR-TB countries as prepared by Stop TB partnership.