Shigella Flashcards
Shigella is closely related to ______
E. coli
Shigella is an important cause of _______
Dysentery
- common in monkeys
- dogs may secrete organism after being infected by people, but they are resistant to disease
Pathogenesis of shigella
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
Shigella mobilizes ____ to invade directly into adjacent colonic epithelial cells
Actin
Virulence factors of Shigella
- type 3 secretion system
- secreted effectors
- all encoded on a large virulence plasmid
S. dysenteriae
Produce Shiga toxin
- targets local endothelial cells
- inactivates 60S ribosomes and leads to inhibition of protein synthesis
Disease
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
Edwardsiella ictaluri
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
Acute versus chronic ESC
- acute: rapid mortalities, enteric septicemia, ascites
- chronic: decreased production, neurologic signs, erosion or ulcer on dorsal frontal bone
Edwardsiella tarda
Opportunist in fish and mammals
- catfish: emphysematous putrefactive disease
Edwardsiella piscicida
Enteric septicemia similar to ESC in channel catfish and in hybrids
- occurs in summer months
Edwardsiella anguillarum
Causes disease in eels in Japan/China
