Lepra bacilli are best cultured in

Footpad of mouse: lepra bacilli multiply in the footpad of mice kept at a low temperature (20 deg). This has become the standard procedure for experimental work with the bacillus. Following intradermal injection into the footpad of mice, a granuloma develops at the site in 1-6 months. If cell-mediated immunity is suppressed by thymectomy or the administration of an anti-lymphocyte serum, generalised infection is produced, simulating lepromatous leprosy. Ref: Textbook of microbiology; Ananthanarayan and paniker's; 10th edition; Pg: 372