Multi-drug-resistant tuberculosis is generally defined as infection with M. tuberculosis strains that are resistant to isoniazid and rifampin, the first-line antibiotics for treating tuberculosis. Drug-resistant tuberculosis has reached new levels of concern because of the recent identification of strains that are resistant not only to rifampin and isoniazid but also to any fluoroquinolone and at least 1 of the second-line injectable agents (amikacin, kanamycin, and capreomycin); this type of drug-resistant tuberculosis has been designated extensively drug-resistant tuberculosis.
Multidrug-resistant tuberculosis (TB) resistant to fluoroquinolones and streptomycin but susceptible to second-line injection therapy has a better prognosis than extensively drug-resistant TB.
