ABSTRACT
The observation that live Mycobacterium leprae on entry into macrophages from lepromatous leprosy patients reduced the number of EA rosetting macrophages, was extended to macrophages from Swiss white mice also. Further, the fact that dead Mycobacterium leprae do not bring about such a change in macrophages from mice, allowed us to develop this into a bacterial viability testing system. Thus drug treated macrophages in the presence of Mycobacterium leprae showed normal rosetting ability if Mycobacterium leprae are inactivated by the drug, but showed reduced level of rosetting when bacteria were not susceptible to the drug. It was shown that a drug like dapsone, does act on Mycobacterium leprae based on its permeability, quantity available inside the macrophages and inhibition of its action by Para amino benzoic acid. The inactivation of Mycobacterium leprae by sulphone and rifampicin was also proved by the flourescence diacetate method, which showed poorly viable bacteria after exposure to drugs. Thus it has been possible to develop a rapid drug screening method for testing the activity of unknown compound against Mycobacterium leprae.