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In the industrialized world, many people believe that tuberculosis (TB) is a disease of the past, yet it represents a leading infectious cause of deaths worldwide. In 2008 there were an estimated 9.4 million new cases of TB and 1.8 million deaths. More than 2 billion people globally are believed to be infected with Mycobacterium tuberculosis, the bacterium that causes TB (these individuals are said to have 'latent TB infection' [LTBI]), and approximately 10% of those infected will become actively sick with TB at some point in their life.[1] The risks of developing active TB are much higher for individuals infected with HIV or who have an otherwise compromised immune system. An estimated 10 million people are currently co-infected with HIV and M. tuberculosis,[2] and present anti-TB drugs, particularly the rifamycins, interact with key antiretroviral agents, rendering coadministration difficult, especially in resource-limited environments.[3] Currently recommended first-line TB treatment regimens require a minimum of 6 months of multidrug therapy, resulting in challenges with patient adherence. The result of inadequate therapy, whether due to misprescribing or poor compliance, is often outgrowth (and transmission) of drug-resistant strains. Five percent of all TB cases are now estimated to be multidrug-resistant TB (MDR-TB; resistant to at least isoniazid and rifampicin, considered by many to be the two most important drugs in first-line treatment) and there were approximately 440 000 new cases of MDR-TB in 2008.[4] In some regions of the world where public health systems have been inadequate to promptly detect and treat TB, more than 20% of new TB cases are now MDR-TB, indicating that primary transmission of drug-resistant strains is becoming a major issue.[1] In 2006, M. tuberculosis strains resistant to all of the most effective first- and second-line drugs were identified for the first time (initially in an outbreak in HIV-positive TB patients in South Africa) and termed extensively drug-resistant TB (XDR-TB).[5] Such strains have now been identified in 58 countries, virtually every country in which they have been looked for.[4] MDR-TB and XDR-TB are much more difficult and costly to treat than drug-sensitive TB (DS-TB), and in most cases are never treated with appropriate regimens, leading both to ongoing transmission and high fatality rates. In 2009, the WHO estimated that less than 2% of global MDR-TB...