3.30 Spirochetes

Microbiology review for the USMLE Step 1 Exam

• Spirochetes are spiral or corkscrew-shaped bacteria that stain gram negative.
• They have a unique endoflagella that distinguishes them from other species of bacteria.
• The endoflagella rotates within the periplasmic space and causes the bacteria to move, acting as its own propeller.
• Borrelia burgdorferi, Treponema pallidum, and Leptospira interrogans are the three important species of spirochetes to know.
• Borrelia burgdorferi causes Lyme disease, which is spread from wildlife to ticks and then to humans.
• The deer tick, also known as ixodes scapularis, is associated with Borrelia burgdorferi, but deer are not the reservoir for the bacteria.
• Lyme disease presents in three stages: erythema migrans (bulls-eye rash), flu-like symptoms, Bell's palsy, myocarditis, transient myalgias, arthritis, and neurological symptoms like encephalopathy and peripheral neuropathy.
• Treponema pallidum causes syphilis, which presents in stages: primary (chancre), secondary (rash), latent, and tertiary (gummas, neurological symptoms).
• Leptospira interrogans causes leptospirosis (Weil's disease), which is spread from infected animal urine to humans through broken skin, mucous membranes, or ingestion.
• Leptospirosis presents with flu-like symptoms, jaundice, renal failure, and meningitis.