Which of the following range shows the generation time for leprosy bacillus?

M. leprae cell division is by transverse fission. In mice, and presumably in man, it divides every 12-13 days (growth rate, mean generation or doubling time). This is a uniquely slow rate of multiplication even for slow-growing mycobacteria (M. tuberculosis, which also belongs to the slow-growing group, divides in about 20 hours), and is consistent with the long incubation period of the disease and its chronicity.