Syphilis is caused by what type of microorganism?

• A. Virus
• B. Bacterium
• C. Fungus
• D. Protozoan

Answer: (B)

Syphilis is caused by a bacterium. The specific organism is Treponema pallidum, a slender spiral-shaped bacterium known as a spirochete. This means the infection is bacterial, not viral, fungal, or protozoan. Because it’s a bacterial infection, antibiotics such as penicillin are effective treatments. In contrast, viruses require host cells to replicate, fungi are a different group of eukaryotic organisms, and protozoa are single-celled eukaryotes as well, but none of them are the cause of syphilis. Understanding that it’s a bacterial infection helps explain both the appropriate treatment and how it spreads.