Evidence for the generation of active oxygen by isoniazid treatment of extracts of Mycobacterium tuberculosis H37Ra.

Crude extracts of Mycobacterium tuberculosis H37Ra, an isonicotinic acid hydrazide (isoniazid) (INH)-susceptible strain which has peroxidase activity, catalyzed the production of catechol from phenol in the presence of INH and H2O2 as shown by the development of the 444-nm absorption peak of oxidized catechol product. Extracts of the INH-resistant strain of M. tuberculosis H37Ra, which has no peroxidase, did not catalyze the reaction. The rate of development of the 444-nm peak increased proportionately with increased superoxide dismutase concentrations. The hydroxyl radical (. OH) scavengers dimethylsulfoxide and mannitol inhibited the reaction. Isonicotinamide, isonicotinic acid, and nicotinic acid could not replace INH.