[Sensitivity to dapsone, sulfamethoxypyridazine and ethionamide of mycobacterium leprae taken from patients treated by the drugs].

Suspensions of M. leprae from skin biopsies of patients treated with dapsone (DDS) (four cases), sulfamethoxypyridazine (SMP) (six cases), and ethionamide (ETH) (seven cases), were inoculated into mouse foot pads and their sensitivity for the different drugs determined. Two strains were DDS resistant. Resistance appeared after 13 and 14 years respectively after the start of treatment. Five strains were isolated from patients treated with SMP. Relapses during sulfonamide treatment are considered to be due to the low effective serum concentrations reached by SMP, a situation which is aggravated by irregularities in drug intake. Fortunately all strains were sensitive to SMP and DDS as well. Four strains were ETH resistant. ETH resistance at the present moment reaches 4% and appeared in two cases six years after the start of treatment. It is concluded that SMP is not indicated for the treatment of multibacillary leprosy and that ETH can be used only in association with other drugs during the introductory phase of treatment of multibacillary forms of leprosy.