Primary dapsone resistance in China.

Ninety-seven strains of Mycobacterium leprae recovered from patients with previously untreated multibacillary leprosy were tested for dapsone susceptibility. The specimens originated from Shanghai Municipality, Jiang-su Province and Fu-jian Province. Approximately 28% of the strains either did not infect the mice or the results of susceptibility were inconclusive due to the low proportion of viable organisms in the bacterial populations. Among the 70 strains in which dapsone susceptibility could be tested in mice, 31 (44%) strains were found with primary dapsone resistance. Although the majority of the primary dapsone resistant strains were shown to be of a low- or intermediate-degree, one-sixth of them were of high-degree resistance.