Which organism is associated with syphilis?

• A. Treponema pallidum
• B. Borrelia burgdorferi
• C. Bacillus subtilis
• D. Staphylococcus aureus

Answer: (A)

Treponema pallidum, a slender, corkscrew-shaped spirochete, is the organism associated with syphilis. It’s a fastidious bacterium that is not easily cultured in ordinary media, so it’s often identified in lesions by dark-field microscopy or special staining techniques. Transmission is primarily through sexual contact, and infection progresses through stages (such as a chancre, rashes, and sometimes later complications) caused by this organism. The other organisms listed are linked to different diseases—Borrelia burgdorferi causes Lyme disease; Bacillus subtilis is mainly a nonpathogenic environmental bacterium (used in labs); Staphylococcus aureus causes a range of skin, soft tissue, and systemic infections but not syphilis.