To achieve these objectives the investigators propose an innovative variation on early bactericidal activity (EBA) study methodology. Patients at risk for MDR TB will be screened for RMP resistance and INH resistance using molecular assays. In those with RMP-resistant or INH-resistant TB, the investigators will quickly perform phenotypic DSTs using the direct method in the Bactec Mycobacterium Growth Indicator Tube (MGIT) 960 system, so results will be available within 14-21 days. If the DST results show, for example, RMP resistance but susceptibility to RBT, consenting patients will be treated with RBT by itself for 10 days. The investigators will assess its effect with serial quantitative sputum cultures. If the concentration of viable bacteria decreases significantly, the investigators will interpret this to mean the drug is having an effect. If not, the drug is ineffective. After 10 days, the patients will resume individualized multidrug treatment based on the full set of DST results.