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: Microbiology
Which of the following organism does not satisfy Koch's postulate? 
Select and explain. 
A. M.TB, B. M.Lepra, C. M.Avium, D. Pneumococcus
B: M.Lepra
Answer: B: M.Lepra 
Explanation: 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.