Abstract
Summary
One hundred twenty-three viable isolates of M. leprae from skin biopsies of leprosy patients have been tested for sulfone resistance in the mouse foot pad since 1970. In 33 strains, growth occurred in animals fed 0.0001% (w/w) dapsone, but not at higher concentrations; in 22, growth occurred at 0.001 and 0.0001% (w/ w) dapsone, but not at the higher concentration; and in 20 isolates, growth occurred at all three concentrations, 0.01, 0.001, and 0.0001% (w/w) dapsone. In each group, in animals fed the highest concentration of dapsone at which growth occurred, the number of bacilli harvested was significantly less than that in controls. Thus 75 strains of M. leprae had some degree of sulfone resistance, and with each degree of sulfone resistance, there was a threshold above which dapsone could still inhibit multiplication of the resistant strain in the mouse foot pad. This finding, in light of the probable mechanism of action of sulfones and mechanism of bacterial resistance to sulfones, strongly implies that maximal subtoxic dosages of dapsone are indicated in all leprosy patients with multibacillary disease treated with this drug.
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