<prompt> MDR tuberculosis is defined when M. tuberculosis shows resistance to -Isoniazid RifampicinIsoniazid PyrazinamideRifampicin PyrazinamideRifampicin Ethambutol  <response>: Ans. is a i.e., Isoniazid Rifampicin Multidrug-resistant TB MDR-TB are by definition infected with strains of Mycobacterium tuberculosis resistant to isoniazid and rifampin. Extremely drug resistant TB XDR-TB due to MDR strains that are resistant to all fluoroquinolones and to at least one of three second-line injectable agents amikacin, kanamycin, and capreomycin. Following are definitions of drug resistant tuberculosis :Definitions of drug-resistant tuberculosis51 Drug-resistant tuberculosis: tuberculosis caused by an isolate of mycobacterium tuberculosis that is resistant to least 1 of the first-line antituberculosis drugs: isoniazid, rifampin, ethambutol, pyrazinamide, or streptomycin Monoresistance: resistance to 1 antituberculosis medication. Multidrug-resistant tuberculosis: tuberculosis caused by an isolate of M tuberculosis that is resistant to the 2 most effective first-line drugs-isoniazid and rifampin-and possibly other antituberculosis drugs. Extensively drug- resistant tuberculosis: multidrug-resistant tuberculosis that is also resistant to the most effective second-line drugs, fluoro-quinolones, and at least 1 of the 3 injectable second-line drugs used to treat tuberculosis amikacin, kanamycin, or capreomycin and, possibly, to other antituberculosis drugs. 