Drug Resistant TB: o Multidrug Resistance TB (MDR): It is TB that does not respond to at least isoniazid and rifampicin (2 of the most powerful first line drugs). o Extensively drug-resistant tuberculosis (XDR-TB): It is resistant to at least four of the core anti-TB drugs. It involves multidrug-resistance (MDR-TB), in addition to resistance to any of the fluoroquinolones (such as levofloxacin or moxifloxacin) and to at least one of the three injectable second-line drugs (amikacin, capreomycin or kanamycin). o Totally drug-resistant tuberculosis (TDR-TB): TB which is resistant to all the first- and second-line TB drugs.