The multidrug-resistant tuberculosis (MDR-TB) epidemic in the Irkutsk oblast of Eastern Siberia is arguably the most severe in the world. The investigators have found that in the Irkutsk TB Dispensary, the referral hospital for the oblast (state), patients with HIV and primary MDR-TB (no prior history of TB treatment) suffered poor outcome during the inpatient phase of treatment. It was also found that genotypic drug-resistance mutations only partially explain the extent of phenotypic resistance that is so widespread in Irkutsk. Suboptimal serum anti-TB drug concentrations amplify such phenotypic resistance and work in other settings has demonstrated the importance of optimizing pharmacokinetics to improve TB outcome. Such foundational work in anti-TB/antiretroviral drug concentrations is lacking for drugs used in the treatment of MDR-TB, and absent in the HIV-infected population. Furthermore, the investigators have found that HIV infection in Irkutsk was associated with the Beijing TB genotype similar to other high burden settings, and that overall mortality was more frequent in those with the M. tuberculosis sublineage Beijing MIT17. Thus taken together the investigators hypothesize that the high early TB mortality in Irkutsk is due to a combination of complex MDR and extensively drug resistant (XDR)-TB that is incompletely diagnosed and incompletely treated, poor anti-TB/antiretroviral pharmacokinetics that lead to low efficacy and increased circulation of hyper-transmissible and virulent M. tuberculosis sublineages.