GI Infections - E. coli Flashcards
How many groups of pathogenic E. coli cause intestinal infection?
6
What are the 6 distinct groups of pathogenic E. coli that cause intestinal infection?
1) ETEC: enterotoxigenic E.coli
2) EHEC: Enterohemorrhagic E.coli
3) EAEC Enteroaggregative E.coli
4) DAEC Diffuse-aggregative E.coli
5) EPEC Enteropathogenic E.coli
6) EIEC Enteroinvasive E.coli
What are the features of E. coli?
Gram-negative rod
Family: Enterobacteriaceae
Motile: multiple peritrichous flagella
Facultatively anaerobic
What are the sources of E. coli?
Environment: bovine faeces: community farms, water. human carriers, etc
Food: Undercooked or raw burgers (ground beef) Unpasteurised fruit juices Dry-cured salami Brussel sprouts Lettuce Game meat Cheese curds Raw milk
Describe the pathogenesis of E. coli infection
Intimate attachment to intestinal epithelial cells and effacement of the brush border
These enterocytes exhibit dramatic loss of microvilli & rearrangement of cytoskeleton elements with proliferation of filamentous actin beneath areas of bacterial attachment
Produce one or more phage encoded (shiga) toxins –
cytotoxic to colonic and renal endothelial cells
- Stx-1 and Stx-2 similar in structure to classic Stx produced by Shigella dysenteriae type 1
- destroy ribosomes by the removal of a single adenine residue from the 28S rRNA: results in the death of the cell.
Haemolysins – disrupt RBC membrane
Local and systemic spread of toxins from the GI tract cause endothelial damage leading to blood loss and most severe symptoms
What is the infectious dose for E. coli?
Very low, less than 100 organisms
What is the incubation period for E. coli infection?
3-4 days
What are the symptoms for E. coli infection?
Mild diarrhoea to bloody diarrhoea (haemorrhagic colitis), abdominal cramps,
Lasts 1 week
Loss of fluid from circulatory system and toxins can cause:
- haemolytic uraemic syndrome (HUS) in 10% of patients after 5-13 days after diarrhoea onset
- acute renal failure, haemolytic anaemia and thrombocytopaenia (lowered platelets)
- usually occurs in young children or elderly
Who is susceptible to E. coli infection?
All ages
• elderly, children younger than 5, immunocompromised, pregnant women are more likely to develop serious complications
How is E. coli infection treated?
Most cases no antimicrobial therapy – controversial as one hypothesis states some antibiotics can increase Shiga toxin expression and thus kidney damage
Fluid and electrolyte replacement
HUS may require dialysis
How is E. coli infection confirmed?
Lab diagnosis: • Stool culture - VTEC O157 antiserum - Commercial biochemical tests - Send to ref lab: RT-PCR
