<prompt> Most common cause of Non-gonococcal urethritis isMeningococciEscherichia coliChlamydia trachomatisMycoplasma  <response>: The most common cause of non-gonococcal urethritis is C.trachomatis. Other common organisms are ureaplasma ureolyticum and Mycoplasma hominis. Ref: Ananthanarayan and Paniker;s Textbook of Microbiology, 9th edition; pg no: 234 