Shigella spp.

Question 1

What are the four species of Shigella?

Answer 1

S. dysenteriae
S. flexneri
S. boydii
S. sonnei

Question 2

Which Shigella species causes the most severe disease?

Answer 2

S. dysenteriae - it produces the Shiga toxin

Question 3

Innculum size of Shigellas

Answer 3

Small - which means they are also acid resistant (acid resistance is induced upon anaerobic growth conditions)

Question 4

Shigella invasion

Answer 4

Invades basolateral surface of epithelial cells.
Invades the M cells and is released into the lamina propria, where it is ingested by macrophages. Proteins then lyse the phagosomal vesicle, and it spreads intracellularly, facilitated by IcsA (an ATPase that causes actin polymerization)

Question 5

M cells

Answer 5

Naturally phagocytic epithelial cells. Uptake shigella and put them in lower cell levels where other immunity cells are. The M cells give the body a place to put stuff before they decide what to do with them

Question 6

Shigella damage

Answer 6

The epithelial cells that ingest Shigella die and sluff off - causing an ulcer. Neutrophils enter the colonic tissue and can be seen in stool. The end result is an inflammatory diarrhea with leukcytes in the stool.

Question 7

What species of Shigella produce Shiga toxin?

Answer 7

Shigella dysenteria. The shiga toxin kills epithelial and endothelial cells, disrupting Na absorption, causing more water loss and diarrhea.