1-19 Spirochetes and Vibrios

Question 1

What are some exapmles of spirochetes?

Answer 1

• Treponema: Syphilis, yaws, pinta
• Leptospira: Leptospirosis
• Borrelia: Lyme Disease, relapsing fever

Question 2

What are some recurring themes for spirochete infections?

Answer 2

• Wide variety of transmission methods
• Cross easily into bloodstream; some also cross blood-brain barrier
• Primary virulence factors are for immune evasion, which can decrease the host’s immune response, meaning . . .
• . . . no vaccines

Question 3

What is the pathogenesis of T. pallidum?

Answer 3

• Congenital syphilis: Treponemes readily cross placenta and infect fetus, resulting in a 40-50% chance of miscarriage/stillbirth/neonatal death
• T. pallidum penetrates mucous membranes/small abrasions, grows in blood vessel endothelium, and enters the lymphatics and bloodstream
• The CNS is invaded relatively early, though symptoms take years to develop
• Though the host raises specific anti-treponemal antibodies, immunity is incomplete; the surface of spirochetes is nonimmunogenic, and spirochetes down-regulate TH1 cells

Question 4

How are spirochete infections diagnosed?

Answer 4

• Diagnosis is challenging because of a wide variety of symptoms and several “phases” as spirochetes invade new organs
• T. pallidum (syphilis) is too small for standard microscopy; B. burgdorfi (Lyme Disease) has no reliable laboratory diagnostic
• Eye exam can be very useful (Argyll-Robertson pupil = hallmark of neurosyphilis, conjunctival suffusion and uveitis in leptospirosis)

Question 5

How are spirochete infections treated?

Answer 5

• If caught early, curable by standard antibiotics: little resistance
• If caught late, infection can still be cured easily, but recovery of nerves and immune system can take months to years, if ever
• Jarisch-Herxheimer reaction to treatment: flu-like symptoms occur 24h after antibiotic treatment, last 24-48h

Question 6

What are the stages of syphilis?

Answer 6

1. Primary syphilis: painless chancre at site of transmission 3-6wks later, heals 3-12 wks; highly infectious
2. Secondary syphilis: 4-10wks, systemic symptoms, mucocutaneous lesions of variable types, condylomata lata, patchy alopecia
3. Tertiary syphilis: 1/3 untreated, fatalities possible; gummatous syphilis; cardiovascular syphilis (>10yrs); neurosyphilis

Question 7

What is Lyme disease? What is its mode of transmission, pathogenesis, process, and treatment?

Answer 7

• Tick-borne infection common in the Northeast US in the summer; reservoirs are small rodents and deer
• Lyme requires 24h to transmit; prompt removal of ticks can prevent disease
• 3 phases: skin infection (rash common) → immune/neurological issues → Chronic Lyme with more severe immune/neuro issues, fibromyalgia
• Antibiotic treatment: doxycycline for up to a month (contraindicated w/ pregnancy), Jarisch-Herxheimer reaction may help confirm diagnosis

Question 8

What are vibrios?

Answer 8

• Curved, Gram(-) rods
• Most vibrio pathogens are ocean-dwelling; several are halophiles
• Primarily cause fecal-oral gastroenteritis
• May also infect wounds contaminated by seawater or ocean debris
• H. pylori causes peptic ulcers

Question 9

How are vibrios transmitted?

Answer 9

• Fecal-oral route. Ugh
• Can also infect wounds contaminated by seawater or ocean debris
• Peptic ulcers

Question 10

What is V. cholerae?

Answer 10

• Curved, comma-shaped, motile Gram(-) rod
• Epidemic in London in 1854: John Snow and the Broad Street pump
• Transmitted by fecal-oral route; travels to untreated water or undercooked shellfish
• High infectious dose, usu. killed by stomach acid
• Surviving bacteria reach the small intestine, secrete mucinase to clear the path to the brush border, attach, and colonize
• After colonizing, bacteria secrete choleragen (A-B subunit enterotoxin that interferes with signal transduction), causing massive watery diarrhea
• Dehydration and electrolyte imbalance
• Infection is self-limited in a previously-healthy host