Enteric Bactieria 1 (1) Flashcards
(33 cards)
Describe the following for Shigella:
Gram stain Fermenting H2S status Mobility Respiration
Gram (-) rod Non-lactose fermenting H2S (-) Nonmotile Facultative Anaerobe
What lab technique can halp differentiate E. coli and Shigella?
MacConkey Agar
How does MacConkey Agar work?
It selects for lactose fermenters (E. coli)
Describe the infectious dose of Shigella?
Very low (<100 IUs)
What are two possible complications of Shigella?
1- Reiters syndrome
2- HUS
What cells does shigella invade?
Distal ilium and colon epithelium
How does shigella escape macrophages?
It induces apoptosis of macrophages
How does Shigella infect cells once it has escaped macrophages?
T3SS mediated entry into the backside of intestinal epithelial cells and neighboring cells
What is the mechanism of the shiga toxin?
Protein systhesis inhibition
Where is the shiga toxin encoded?
plasmid
What causes HUS?
Shiga toxin escapes into bloodstream
What occurs in the pathogenesis of HUS?
Shiga toxin sets off a immunological/hematological cascade leading to acute hemolysis, renal failure, uremia, and disseminated intravascular coagulation (DIC)
Symptoms of shigella?
Fever, dehydration, severe headache, lethargy, diarrhea progresses from watery to bloody with mucus
Symptoms of HUS?
Fever, dehydration, hemolysis, thrombocytopenia, uremia requiring dialysis
What age group is most effected by Shigella ?
The young (particularly <5yo)
What can host factor can worsen a shigella infection?
Malnourishment
What laboratory results are diagnostic of HUS?
Schistocytes, Decreased platelets, increased PMNs increased lactate dehydrogenase
Treatment for shigella?
Rehyrdrate!
No anti-diarrheals
Antibiotics once r/o E. coli
Describe the following for E. coli:
Gram stain Fermenting H2S status Mobility Respiration
Gram (-) rod Lactose fermenting H2S (-) Motile or non-motile Facultative anaerobe
What GI symptoms/ diarrheal illnesses are caused by the following E. coli strains?
Enterotoxigenic E. coli (ETEC)
Enteropathogenic E. coli (EPEC)
Enteroinvasive E. coli (EIEC)
Enterohemorrhagic E. coli (EHEC)
Enterotoxigenic E. coli (ETEC) is a cause of traveler’s diarrhea.
Enteropathogenic E. coli (EPEC) is a cause of childhood diarrhea
Enteroinvasive E. coli (EIEC) causes a Shigella-like dysentery.
Enterohemorrhagic E. coli (EHEC) is infected by phage STX, produces Shiga toxin, causes hemorrhagic colitis or hemolytic-uremic syndrome (HUS).
Name some virulence factors of E. coli
T3SS
T4SS
Shiga toxin
Enterotoxins
Pili/ fimbrae
What is the mechanism of the enterotoxin of E. coli?
It is an exotoxin that forces host ells to release fluids (and K+)
T/F: HUS is a purely toxigenic process.
True
What are 2 important factors that influence the development of HUS?
1- Capillary occlusion
2- Cytokine dysregulation (increased)
