Which of the following organism does not satisfy Koch's postulate?

It is not possible to culture M.Lepra in culture medium, so it doesnt follow Koch's postulate. Koch's postulate defines the criteria for establishing a causal relationship between a suspect pathogen and disease. According to the postulate a suspected bacterium must be found in all organisms suffering from the disease but not healthy ones, suspected bacterium must be isolated from a diseased organism, isolated bacterium should cause disease when introduced into a healthy organism and bacterium must be reisolated from the diseased organism. Ref: Textbook of Microbiology By Ananthanarayan And Paniker, 7th edition page 370.