In vitro resistance test of human leprosy bacilli to anti-leprous drugs.

Sensitivity to anti-leprous drugs of M. leprae isolated from an L-type leprosy patient was tested using M--Y 14b liquid medium by direct and indirect methods. The results revealed that the strain, SR61-L74, was almost completely resistant to DDS, and responded only to the long-term administration of Streptomycin and Isoniazid. However, the strain was completely sensitive to rifampicin which had never been administered previously. The subsequent administration of rifampicin resulted in a rapid improvement of the patient's clinical symptoms. It can be concluded that the in vitro method, both direct and indirect, to test the sensitivity of M. leprae to anti-leprous drugs is economic, and accordingly available practically as one of the routine examinations in the laboratory of ordinary leprosaria. This must be very beneficial to the treatment of leprosy patients.