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The most direct way to diagnose syphilis in the early stages is by dark-field examination or immunofluorescence staining of mucocutaneous lesions. The highest yield comes from examining serous transudate from moist lesions such as the primary chancre, condylomata latum, or mucous patches, which have the largest number of organisms. Darkfield examination may not be able to distinguish nonpathogenic treponemes that reside in the mouth from T. pallidum, so specific direct fluorescent antibody staining should be done on oral specimens.

For darkfield examination, lesions should be rinsed with nonbactericidal saline and lightly abraded with dry gauze so as not to induce bleeding. The resulting serous exudates can be squeezed onto a glass slide and covered with a cover slip to be examined. Under darkfield examination, a characteristic corkscrew appearance and spiraling movement with flexion about the center establishes the presence of T. pallidum. Dark-field examination must be done immediately after specimen collection so that the organisms remain viable; however, motility is not required for diagnosis by the direct fluorescent antibody test. In addition, because numerous organisms are required for visualization, a negative test finding does not rule out the diagnosis.

Biopsy specimens are sometimes useful to diagnose syphilis. Specific immunofluorescence or immunoperoxidase staining is preferred over silver staining for ease of diagnosis.

Polymerase chain reaction assays can detect T. pallidum in clinical specimens, but this is currently not available for routine use.


Men's Health