Primary dapsone-resistant leprosy in San Francisco.

The dapsone sensitivity of strains of Mycobacterium leprae from 54 multibacilliferous untreated leprosy patients presenting to the United States Public Health Service Hospital in San Francisco, California, U.S.A., from 1978 to 1981 was studied by mouse foot pad inoculation. M. leprae from 53 patients were found fully sensitive to dapsone. M. leprae from one patient were resistant to only the lowest dietary level of dapsone, 0.0001%, since growth of the bacilli was inhibited by higher and clinically easily achievable levels. Mouse plasma dapsone levels confirmed the reliability of the drug-containing diets.