This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
Which of the following range shows the generation time for leprosy bacillus? 
Select and explain. 
A. 8-10 days, B. 10-12 days, C. 12-15 days, D. 15-20 days
C: 12-15 days
Answer: C: 12-15 days 
Explanation: 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.