Activity of amikacin against Mycobacteria in vitro and in murine tuberculosis

Amikacin was found to be a potent inhibitor of clinical isolates of Mycobacterium tuberculosis in vitro. The drug was also active against some, but not all, strains of M. intracellulare, M. kansasii and rapidly growing mycobacteria in concentrations that may be attained clinically. Activity was independent of susceptibility or resistance of the isolates to commonly used antituberculosis agents. Groups of mice were infected intravenously with M. tuberculosis H37Rv and then treated daily with amikacin, streptomycin, isoniazid or kanamycin. One third of the mice in each group were killed 30, 60 and 90 days after infection. Extent of pulmonary disease was recorded and tubercle bacilli were enumerated in lungs. Isoniazid eradicated tubercle bacilli from the lungs within 90 days. The remaining drugs were suppressive. Amikacin was more efficacious than streptomycin or kanamycin given in equivalent or greater dosages. Because of its potent activity in vitro, efficacy in experimental tuberculosis and activity against drug resistant mycobacteria, amikacin merits further study as a potential therapeutic agent for tuberculosis and other mycobacterial infections.