The Sensitivity to Dapsone (DDS) of Mycobacterium Leprae from Patients with and without Previous Treatment

Abstract

Thirty-two isolates of Mycobacterium leprae from 27 patients with leprosy were tested in mice for sensitivity to 0.0001% DDS in the diet. All 11 isolates from previously untreated patients and six from patients with some treatment were sensitive to 0.0001% DDS. This dosage in mice is estimated to produce blood and tissue concentrations of about 0.02 µg per milliliter, or 1/100th the concentrations produced in man by standard dosages of DDS. Since 0.00001% DDS was usually not effective, the usual minimum inhibitory concentration of DDS for M. leprae in untreated patients appears to lie between 0.02 and 0.002 µg per milliliter. Fifteen isolates from 10 other patients with previous treatment were found resistant to 0.0001% or more DDS in the diet of mice. These patients had begun treatment 11 to 20 years previously. Seven had begun with glucosulfone and two with sulfoxone. It seems possible that the irregularity of the DDS supplied by these drugs contributed to the appearance of DDS-resistant M. leprae.