IN-VITRO SUSCEPTIBILITY OF MYCOBACTERIUM-LEPRAE TO OXYGEN-MEDIATED DAMAGE

In order to evaluate factors responsible for the failure of Mycobacter ium leprae to multiply in cell-free cultures in vitro studies were und ertaken to determine the possible poisoning of the organism by hydroxi de and superoxide radicals produced in the growth medium. The superoxi de dismutase activity was very low, 10% of the levels found in armadil lo cells, while measured activity of catalase and glutathione peroxida se was negligible. Susceptibility of M. leprae to hydrogen peroxide wa s enhanced by potassium iodide but not by lactoperoxidase. The additio n of high amounts of catalase completely prevented hydrogen peroxide-m ediated killing of M. leprae. Superoxide generated by the action of xa nthine oxidase on xanthine was lethal to M. leprae, but superoxide dis mutase added to the reaction mixture gave significant protection. Thus superoxide radicals may be a major cause for the sudden termination o f growth of M. leprae in primary cultures and also for failure of subc ultures.