A 23-year-old male had unprotected sexual intercourse with a commercial sex worker. Two weeks later, he developed a painless, indurated ulcer on the glans which exuded clear serum on pressure. Inguinal lymph nodes in both groins were enlarged and not tender. The most appropriate diagnostic test is:: (A) Gram's stain of ulcer discharge, (B) Darkfield microscopy of ulcer discharge, (C) Giemsa stain of lymph node aspirate, (D) ELISA for HIV infection
Answer is B. B i.e. Dark field microscopy of ulcer discharge