Shigella

Question 1

Shigella is closely related to ______

Answer 1

E. coli

Question 2

Shigella is an important cause of _______

Answer 2

Dysentery

• common in monkeys
• dogs may secrete organism after being infected by people, but they are resistant to disease

Question 3

Pathogenesis of shigella

Answer 3

Invades and multiplies in intestinal cells (similar to EIEC)

• no ST or LT produced
• enters thru M cells, transcytosis occurs to basal membrane and is released
• shigella is phagocytosed by resident macrophages, type 3 secretion system induces apoptosis
• released shigella invades colonic epithelial cells thru basal membrane using type 3 secretion system and multiply in cytoplasm

Question 4

Shigella mobilizes ____ to invade directly into adjacent colonic epithelial cells

Answer 4

Actin

Question 5

Virulence factors of Shigella

Answer 5

• type 3 secretion system
• secreted effectors
• all encoded on a large virulence plasmid

Question 6

S. dysenteriae

Answer 6

Produce Shiga toxin

• targets local endothelial cells
• inactivates 60S ribosomes and leads to inhibition of protein synthesis

Question 7

Disease

Answer 7

Early signs of fever, abdominal discomfort, watery diarrhea

• some monkeys develop dysentery (bloody mucoid diarrhea, severe cramps)
• all animals have reduced colonic absorption or net colonic secretion and severe colitis and microabscesses

Question 8

Edwardsiella ictaluri

Answer 8

Enteric septicemia of channel catfish

• only one major serotype that affects channel catfist
• occurs in 22-28 C (spring/fall)
• treat with antimicrobial medicated feed
• bacterin has limited effectiveness, CMI needed

Question 9

Acute versus chronic ESC

Answer 9

• acute: rapid mortalities, enteric septicemia, ascites

- chronic: decreased production, neurologic signs, erosion or ulcer on dorsal frontal bone

Question 10

Edwardsiella tarda

Answer 10

Opportunist in fish and mammals

- catfish: emphysematous putrefactive disease

Question 11

Edwardsiella piscicida

Answer 11

Enteric septicemia similar to ESC in channel catfish and in hybrids
- occurs in summer months

Question 12

Edwardsiella anguillarum

Answer 12

Causes disease in eels in Japan/China