Novel Mutations in ndh in Isoniazid-Resistant Mycobacterium tuberculosis Isolates

Novel mutations in NADH dehydrogenase (ndh) were detected in 8 of 84 (9.5%) isoniazid (INH)-resistant isolates (T110A [n = 1], R268H [n = 7]), but not in 22 INH-susceptible isolates of Mycobacterium tuberculosis. Significantly, all eight isolates with mutations at ndh did not have mutations at katG, kasA, or the promoter regions of inhA or ahpC, except for one isolate. Mutations in ndh appear to be an additional molecular mechanism for isoniazid resistance in M. tuberculosis.