There have been discussions on the role of a novel species of Mycobacterium, M. lepromatosis, in the causation of Leprosy for a long time now. In 2008, Han and colleagues (1) found the novel bacterium as the causative organism behind diffuse lepromatous leprosy. A new paper (2) published in the Proceedings of the National Academy of Sciences (PNAS) has further strengthened the premise of a novel species causing leprosy by conducting a whole genome study.
1. Han XY, Seo YH, Sizer KC, Schoberle T, May GS, Spencer JS, Li W, Nair RG. A new _Mycobacterium_ species causing diffuse lepromatous leprosy. Am J Clin Pathol. 2008 Dec;130(6):856-64. doi: 10.1309/AJCPP72FJZZRRVMM.
2. Singha P, Benjaka A, Schuenemannb VJ, Herbigb A, et al. Insight into the evolution and origin of leprosy bacilli from the genome sequence of Mycobacterium lepromatosis. PNAS. March 18, 2015. doi: 10.1073/pnas.1421504112.