Lyme disease is caused by which type of organism?

• A. Virus
• B. Bacterium
• C. Fungi
• D. Spirochete

Answer: (D)

Lyme disease is caused by a bacterium in the spirochete group, specifically Borrelia burgdorferi. Spirochetes are slender, corkscrew-shaped bacteria that move with axial flagella between their membranes, giving them a distinctive twisting motion that helps them invade tissues and spread. This makes the spirochete designation the most precise way to describe the organism. It is not a virus, which lacks cellular structure and replicates only inside host cells, and it is not a fungus. Describing it as spirochete communicates both its bacterial nature and its characteristic shape, aligning with how this pathogen is understood in medical microbiology.