The causative agent of syphilis is which organism?

• A. Borrelia burgdorferi
• B. Neisseria gonorrhoeae
• C. Chlamydia trachomatis
• D. Treponema pallidum

Answer: (D)

Syphilis is caused by Treponema pallidum, a slender spiral bacterium in the spirochete group. It’s transmitted primarily through sexual contact and presents in stages such as a painless chancre, followed by rashes and potential systemic involvement if untreated. Treponema pallidum is characteristically a spirochete with corkscrew-like motion and is hard to visualize with standard Gram staining, so clinicians rely on dark-field examination of lesions or specific serologic tests for diagnosis. Among the options, this organism is the one responsible for syphilis, while the others cause different diseases: Borrelia burgdorferi causes Lyme disease, Neisseria gonorrhoeae causes gonorrhea, and Chlamydia trachomatis causes chlamydia.