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31 Cards in this Set

  • Front
  • Back
What is E. coli?
Lactose-fermenting
Oxidase-negative
G-
Enteric rod
Where is E. coli found?
Part of the normal flora of the human gut.
What are three metabolic characteristics of E. coli?
1) Facultative anaerobes
2) Ferment glucose and lactose
3) Reduce nitrates to nitrites.
How is E. coli transmitted?
Fecal-oral and food-borne transmission.
What enables E. coli to adhere to the epithelium of the GI tract?
Pili or fimbriae
How are E. coli strains typed?
O antigen
H antigen
K antigen
What is teh most common clinical manifestation of E. coli infection?
Diarrhea
What extraintestinal diseases does E. coli commonly cause?
1) UTI
2) Cystitis
3) Pyelonephritis
4) Sepsis
5) Neonatal meningitis
6) hemolytic uremic syndrome
7) Endotoxic shock
8) Pneumonia
How is E. coli infection diagnosed?
Culture
biochemical tests
serological tests
Which antibiotics are commonly used to treat E. coli?
Ampicillin
Cefotaxime
ciprofloxacin
Trimethoprim-sulfamethoxazole (Bactrim)
What are five common pathogenic species of E. coli?
1) Enterotoxigenic E. coli (ETEC)
2) Enteropathogenic E. coli (EPEC)
3) Enterohemorrhagic E. coli (EHEC)
4) Enteroinvasive E. coli (EIEC)
5) Enteroadherent E. coli (EAEC)
Which strains cause bloody diarrhea?
EHEC
EIEC
What does ETEC commonly cause?
Traveler's diarrhea
What are two enterotoxins released by ETEC?
1) Heat-labile toxin (LT)
2) Heat-stable toxin (ST)
How many subunits does heat-labile toxin have?
2 subunits
A & B
What is the pathogenesis of heat-labile toxin?
1) Subunit A: activates adenylate cyclase, increases cyclic adenosine monophosphate, increases secretion of water adn chloride ions, and inhibits sodium reabsorption leading to elecrolyte imbalance, hypermotility, and diarrhea (similar to cholera toxin)
2) Subunit B: binds Gm1 ganglioside at the brush border of the small intestine, facilitating entry of Subunit A
3) Heat-Labile toxin is essentially the same as the cholera toxin produced by Vibrio cholerae.
What is the pahtogenesis of heat-stable toxin?
Activates guanylate cyclase in epithelial cells of the small intestine, increasing cyclic guanosine monophosphate and causing fluid seretion.
How does ETEC cause disease?
Attaches to the small intestinal epithelium via pili and produces enterotoxins that cause hypersecretion of chloride ions and block absorption of sodium, resulting in massive amounts of water in the lumen of the gut
What does EPEC commonly cause?
Watery diarrhea in infants.
When does EPEC infection usually take place?
During parturition (birth) or in utero.
How does EPEC caues disease?
Bacteria in the gastrointestinal tract attach to mucosal cells in the small intestine and destroy microvilli with attaching and effacing lesions, also resulting in an inflammatory response.
What is the primary reservoir for EHEC?
Cattle
How does cattle as a reservoir relate to outbreaks of EHEC?
Eating undercooked beef.
What does EHEC commonl cause?
Hemorrhagic colitis and bloody diarrhea?
How does EHEC cause disease?
Attaches to and detroys mucosal cells with attaching and effacing lesions and also produces verotoxin, a Shiga-like toxin that enters the bloodstream causing endothelial damage and platelet aggregation, resulting in throbus formation.
Does EHEC invade the bloodstream?
NO
Only the shiga-like toxin and LPS enter the blood.
What life-threatening condition is associated with EHEC?
Hemolytic uremic syndrome (HUS)
What strain of EHEC has resulted in recent outbreaks and hemolytic uremic syndrome?
E. coli O157:H7
What sugar is not fermented by this strain that is fermented by other strains of E. coli?
Sorbitol
What disease does EIEC cause?
Dysentery (bloody diarrhea and fever) similar to shigellosis.
What disease does EAEC cause?
Traveler's diarrhea and persistent diarrhea in children.