Emergence of fluoroquinolone-resistant tuberculosis in New York City

22 patients infected with fluoroquinolone-resistant Mycobacterium tuberculosis in New York City were identified between January, 1991, and November, 1993. In 16 patients resistance arose as a result of inadequate or inappropriate treatment. 6 patients had primary infection with fluoroquinolone-resistant organisms; 5 acquired the organisms nosocomially. Seven distinct patterns of restriction-fragment length polymorphism were identified in isolates from 21 patients. Fluoroquinolones should be restricted to patients with multidrug-resistant disease or intolerance to other antituberculosis drugs. All patients with multidrug-resistant tuberculosis should be on directly observed therapy.