Crohn's disease may be caused by which one of the following infectious agents?

A possible infectious etiology for IBD includes clostridium difficile, maparatuberculosis, paramyxovirus and helicobacter species, salmonella shigella, campylobacter species. M.para tuberculosis does not have a confirmed disease association and antimycobacterial agents are not effective in treating Crohn's disease. Ref: Harrison's Principles of Internal Medicine, 16th Edition, Pages 1176-78; Davidson's Principles and Practice of Medicine, 19th Edition, Page 808