Instituto Lauro de Souza Lima (ILSL) 1 article published in JoVE Immunology and Infection Optimized Protocols for Mycobacterium leprae Strain Management: Frozen Stock Preservation and Maintenance in Athymic Nude Mice Ana Paula Fávaro Trombone1, Sílvia Cristina Barbosa Pedrini2, Suzana Madeira Diório3, Andréa de Faria Fernandes Belone1, Luciana Raquel Vicenzi Fachin1, Dejair Caitano do Nascimento4, Patricia Sammarco Rosa2 1Department of Pathology, Instituto Lauro de Souza Lima (ILSL), 2Laboratory Animal House, Instituto Lauro de Souza Lima (ILSL), 3Department of Microbiology, Instituto Lauro de Souza Lima (ILSL), 4Department of Pharmacology, Instituto Lauro de Souza Lima (ILSL) Mycobacterium leprae, the causative agent of leprosy, does not grow in vitro. We describe an easy to follow protocol to prepare a bacillary suspension to ensure the maintenance of large quantities of M. leprae for a variety of applications. Protocols for propagation by mouse footpad inoculation, evaluation of viability, freezing and thawing bacillary stock are described in detail.