A man who has a penile chancre appears in a hospital's emergency service. The VDRL test is negative. The most appropriate course of action for the physician in charge would be to
Send the patient home untreated
Repeat the VDRL test in 10 days
Perform dark-field microscopy for treponemes
Swab the chancre and culture on Thayer-Martin agar
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.
Bacteria