Shigella

Question 1

Describe shigella

Answer 1

Ferments glucose, strict human pathogen, causes dysentery.

Question 2

What is shigellas resevoir? Transmission? Prevention?

Answer 2

Human intestinal tract and contaminate food/water; Transmitted by oral-fecal. Can be prevented by hand washing.

Question 3

Describe shigellas pathogenesis.

Answer 3

Passes through small intestine and large intestine; Acid resistant.

1. Enters cell via ‘Trigger mechanism’
2. Escapes phagosome into cytoplasm
3. Spreads from cell to cell on polymerized actin tails.

Question 4

What are shigellas virulence factors?

Answer 4

Ipa proteins and IcsA, IcsP, and VirA

Question 5

What role does Ipa proteins play?

Answer 5

IpaA, IpaB, Ipac, IpaD; Adherence, invasion and escape from endocytic vesicle. Secreted by Type 3 secretion system

Question 6

What role does IcsA, IcsP, and VirA play?

Answer 6

Responsible for INTRACELLULAR SPREAD on polymerized actin tails.

Question 7

Describ the pathogenesis of shigella

Answer 7

IpaB inserts into phospholipid bilayer, IpaC forms a translocon pore; IpaA causes trigger uptake and endosomal membrane lysis. Cell multiplies in cytoplasm.

Question 8

What happens once shigella enters the cytoplasm?

Answer 8

It spreads laterally to other epithelial cells; Host cell actin polymerizes and propelles bacteria into adjacent cells. VirA degrades tubulin, creating a tunnel in the microtubule network. Enters new cell, repeat.

Question 9

What causes the initial watery diarrhea in a shigella infection?

Answer 9

Enterotoxins Shet 1 and 2

Question 10

What causes the bloody dysentery?

Answer 10

Macrophage apoptosis causing neutrophil chemotaxis; Formation of surface erosions or ulcers in gut wall; Also causes Acute inflammatory colitis.

Question 11

What are the cardinal signs of shigellosis?

Answer 11

Lower abdominal cramps, bloody stool with abundant neutrophils.

Question 12

Whats the treatment plan of shigella infection?

Answer 12

Antibiotics and rehydration.

Question 13

What does shigella dysenteriae type 1 produce?

Answer 13

Produces shigatoxin; AB subunit toxin. Blocks protein synthesis by degrading 28S RNA

Question 14

What does shigatoxin do to cells?

Answer 14

Decreases sodium absorptin, causes necrosis of epithelium and Hemolytic uremic syndrome.

Question 15

How does shigella evade the host immune system?

Answer 15

Trigger mechanism into non-professional phagocytes and escape into cytoplasm; Actin tails allows bacteria to avoid exposure to immune system.