<prompt> A man who has a penile chancre appears in a hospitals emergency service. The VDRL test is negative. The most appropriate course of action for the physician in charge would be toSend the patient home untreatedRepeat the VDRL test in 10 daysPerform dark-field microscopy for treponemesSwab the chancre and culture on Thayer-Martin agar  <response>: In men, the appearance of a hard chancre on the penis characteristically indicates syphilis. Even though the chancre does not appear until the infection is 2 or more weeks old, the VDRL test for syphilis still can be negative despite the presence of a chancre the VDRL test may not become positive for 2 or 3 weeks after initial infection. However, a lesion suspected of being a primary syphilitic ulcer should be examined by dark-field microscopy, which can reveal motile treponemes. 