A man presents to a STD clinic with urethritis and urethral discharge. Gram stain shows numerous pus cells but no microorganism. The culture is negative on the routine laboratory media. The most likely agent is -

Ans. is 'a' i.e., Chlamydia trachomatis . STD in man presenting with urethritis is usually caused by following organisms :- . Neisseria Gonorrhoeae . Ureaplasma urealyticum . HSV . Chlamydia trachomatis . Trichomonas vaginalis . So, from the options given in the question our choice comes to Neisseria gonorrhoeae and Chlamydia trachomatis. . Two points our the diagnosis of chlamydia i.e. a) Presence of pus cells with absence of any microorganisms on gram stain. Chlamydia can't be stained by ordinary stains,it needs to be stained by specialised stains. b.)Chlamydia does not grows on Ordinary Culture and medium but can only be cultivated by cell lines(Mc.Coy) or Embryonated egg.