Which organism is primarily associated with syphilis?

• A. Mycobacteria
• B. Treponema pallidum
• C. Haemophilus influenzae
• D. Pseudomonas aeruginosa

Answer: (B)

Treponema pallidum is the organism most associated with syphilis. It’s a slender spirochete transmitted mainly by sexual contact and, if untreated, can progress through multiple stages affecting many body systems. In the lab, this organism isn’t reliably cultured on ordinary media, so diagnosis often relies on dark-field examination of lesion material or on serologic testing (screening non-treponemal tests like VDRL or RPR followed by a confirmatory treponemal test). The other organisms listed cause different infections—Mycobacteria lead to TB and leprosy, Haemophilus influenzae to meningitis and other infections, and Pseudomonas aeruginosa to opportunistic hospital-acquired infections—so they’re not linked with syphilis.