Pathology of typhoid fever

Question 1

Discuss the pathogenesis of non-typhi infections

Answer 1

1. Large inoculum swallowed
2. Passage through gastric acid barrier
3. Multiplication in bowel (enterotoxin)
4. Penetration of epithelial cells
5. Bacteria exit distal cell -> lamina proprietary -> PMN response (prevents spread)
6. Prostaglandin release -> incr cAMP
7. Diarrhea from secretion excretion overcoming absorptive capacity
8. Small, shallow ulcers w/ erythema

Question 2

What are the differences in the pathogenesis of typhi infections from non-typhi

Answer 2

1. Mononuclear inflammatory response
2. Inhibition of O2 burst after phagocytosis -> bacteria not killed -> enter bloodstream -> disseminate via RES
3. Different immune systems (circulating immune complexes and increased suppressor T cells)
4. Inflammation is maximal in Peyer’s patches -> endotoxin release
5. Intracelluar location

Question 3

What is the difference in toxins in typhi vs non-typhi?

Answer 3

Typhi - endotoxin
Non-typhi - enterotoxin

Question 4

Discuss the stages of typhi infection

Answer 4

1. Incubation
   - 10-14d
   - mild enteritis
   - lymphoid hyperplasia
2. Invasion
   - 1w
   - continuous bacteremia with increasing fever
   - mallory cells
   - emperipolesis (cell phagocytosis)
3. Fastigium
   - 1w
   - constant fever
   - endotoxin release
   - lymphoid tissue necrosis
   - toxaemic changes
4. Decline
   - decreasing temperature
   - lymphoid tissue sloughing
   - oval ulcers
5. Convalescence
   - minimal scarring
   - splenic capsule fibrosis
   - complications

Question 5

Which typhi totemic change in the fastigial phase mimics acute abdomen?

Answer 5

Zencker’s degeneration of the rectus abdominis

Question 6

The absorption of which molecules is not altered during cholera?

Answer 6

Glucose
Sodium