Acute gastrointestinal tract infections caused by E. coli. Differential diagnosis of acute diarrhea.

Question 1

what are the STRAINS OF ECOLI ?

Answer 1

enteropathogenic E. coli

enterotoxin E. coli

enteroinvasive E. coli

enteroaggregative E. coli

enterohemorrhagic E. coli
-MOST COMMON SEROTYPE: O157:H7

Question 2

mode of TRANSMISSION FOR THE DIFFERENT eCOLI STRAINS

Answer 2

reservoir of this pathogen appears to be mainly cattle. In addition, other ruminants such as sheep, goats, deer

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enteropathogenic E. coli
Natural gut flora
 fecal–oral transmission
person to person- so
the infectious dose is likely to be low

enterotoxin E. coli
Fecal contaminated food and water

enteroinvasive E. coli
Natural gut flora
Fecal-oral route; fecal contamination of water, fo

enteroaggregative E. coli
Fecal - oral
contaminated food and water

enterohemorrhagic E. coli
consumption of Undercooked meat, raw leafy vegetables
person-to-person
fecal oral 
contaminated food

Question 3

what are the DIFFERENT CHARACTERISTICS OF DIFFERENT STRAINS OF ECOLI?

Answer 3

all are gram (–) and anaerobes (don`t need Oxygen):
family - enterobacteriacae

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enteropathogenic E. coli
- Usually in children
In contrast with ETEC
disease,
WATERY DIARRHEA
No toxin is produced

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enterotoxin E. coli
- Common cause of traveler's diarrhea
-in young children and developing countries 
-small intestine - SECRETORY DIARRHEA 
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enteroinvasive E. coli
-Sporadic cause of diarrhea
Direct invasion of the intestinal epithelium and formation of enterotoxins → BLOODY DIARRHEA
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enteroaggregative E. coli
-Usually causes persistent diarrhea 
associated with chronic diarrhea and growth
retardation in children
- SECRETORY DIARRHEA 
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enterohemorrhagic E. coli
most common strain producing
 in developed countries.
-MOST COMMON SEROTYPE: O157:H7
BLOODY DIARRHEA

Question 4

what are the IMPORTANT VIRULENCE FACTORS OF DIFFERENT STRAINS OF ECOLI? ///

Answer 4

enteropathogenic E. coli
(Baby diarrhea)\
goes to SI epithelium
aggregation of the bacteria, leads to formation of microcolonies on the epithelial cell surface
mediated by the plasmid- encoded bundle-forming pili
they then inject proteins which destroy microvilli → decrease absorption → ↑osmotic pressure in lumen → watery diarrhea
No toxin is produced

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ENTEROTOXIN E. COLI
-HEAT-LABILE TOXIN
- HEAT-STABLE TOXIN
Heat-labile enterotoxin (AB toxin; two-component protein, similar to cholera toxin): activation of adenylate cyclase → ↑ cAMP levels → ↑ chloride secretion → water efflux into the intestinal lumen → SECRETORY DIARRHEA
Heat-stable enterotoxin: activation of guanylate cyclase → ↑ cGMP levels → ↓ NaCl reabsorption → water efflux into the intestinal lumen → SECRETORY DIARRHEA
NO INVASION OF THE INTESTINAL MUCOSA AND NO INFLAMMATION
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enteroinvasive E. coli

• Direct invasion of the intestinal epithelium and formation of enterotoxins → bloody diarrhea
  (similar to shigella )

osely related by phenotypic and pathogenic properties to
Shigella

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enteroaggregative E. coli
(Persistent diarrhea)
associated with chronic diarrhea and growth
retardation in children

goes to enterocytes of SI
Aggregation (“stacked-brick” pattern) with one another and adherence to intestinal mucosa

mucus secretion is stimulated

leading to formation of thick biofilm which covers the mucosa
→ decrease H2O absorption→ inflammation → watery (possibly bloody) diarrhea

!!!!!!!!TWO GROUPS OF TOXINS!!!!!!!!!! are associated with EAEC:
enteroaggregative heat stable toxin that is antigenically related to the heat-stable
toxin of ETEC and

plasmidencoded toxin.

Both toxins induce fluid secretion diarrhea

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enterohemorrhagic E. coli
GOES TO LARGE INTESTINE EPITHELIUM & SECRETE SHIGA LIKE TOXIN
Shiga-like toxin: bloody diarrhea / hemorrhagic
colitis
HUS in children

fewer than 100 bacteria can produce disease - HIGHLY INFECTIOUS

Question 5

incubation period for different strains of ecoli

Answer 5

ENTEROHEMORRHAGIC

2-10 days

Question 6

clinical features of different strains of ecoli ?

Answer 6

enteropathogenic E. coli
In infants for 2 weeks; 
adults asymptomatic
watery diarrhea  about 2 weeks
Vomiting
Low-grade fever

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enterotoxin E. coli
Symptoms last 3–4 days.
Watery diarrhea
Abdominal cramping
Nausea, possibly vomiting
Fever
Decreased appetite

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enteroinvasive E. coli

rare

Watery first then to bloody diarrhea, possibly with mucus (dysentery) with Fever, chills, malaise
Abdominal cramps

Possibly vomiting

Symptoms similar to shigellosis

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enteroaggregative E. coli
chronic diarreha and growth retardation

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enterohemorrhagic E. coli
1) vomitng 
2)  Bloody diarrhea 
and abdominal tenderness

dehydration,

LITTLE TO NO FEVER

HUS - acute renal failure - thrombocytopenia , microangiopathic anemia complication in those younger than 10 years
- hypertension

Question 7

DIAGNOSIS of different STRAINS OF ECOLI?

Answer 7

enteropathogenic E. coli
enterotoxin E. coli
enteroinvasive E. coli
enteroaggregative E. coli
enterohemorrhagic E. coli

Culture and/or PCR from stool samples

sorbitol - MacConkey agar: pink colonies
Eosin-methylene blue agar: colonies with a metallic green sheen
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Rapid stool immunoassay for Shiga toxin

Check for non-O157 EHEC by detection of Shiga toxins (via enzyme immunoassay) or Shiga toxin-encoding genes (via PCR)

Question 8

TREATMENT FOR ECOLI?

Answer 8

Supportive therapy :
Rehydration and electrolyte replenishment (e.g., oral rehydration salts or solutions; IV fluids)
Clear liquids, easy-to-digest foods
The patient should return to a normal diet as soon as tolerated

antibiotic therapy is generally not recommended

Considered only in cases of severe and/or persistent diarrhea

First-line agents in adults: fluoroquinolones (e.g., ciprofloxacin,

Alternative (drug of choice in children and pregnant women): azithromycin

ANTIBIOTIC THERAPY IS CONTRAINDICATED.!!! - enterohemorrhagic E. coli

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enteropathogenic E. coli
In cases of persistent diarrhea (e.g., loose stools for > 2 weeks) antibiotics may be used.

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enterotoxin E. coli

ANTIBIOTICS MAY SHORTEN THE DURATION OF SYMPTOMS.
Bismuth subsalicylate compounds may decrease the frequency of bowel movements.

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enteroinvasive E. coli
Antimotility agents are contraindicated
in children and in persons with enteroinvasive E coli

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enteroaggregative E. coli

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enterohemorrhagic E. coli

ANTIBIOTIC THERAPY IS CONTRAINDICATED.!!!
Avoid antiperistaltic agents (e.g., diphenoxylate/atropine) since they increase the risk of systemic complications.

Question 9

DD OF ECOLI?

Answer 9

Food poisoning

Bacterial gastroenteritis - Campylobacter, Salmonella, Shigella, Yersinia, Vibrio cholerae, Staphylococcus aureus , clostridium difficile

Norovirus infection
Rotavirus infection

Question 10

PREVENTION OF ECOLI?

Answer 10

Infection can be prevented by avoiding or safely preparing foods
washing hands with soap frequently

Question 11

ECOLI ALSO is the CAUSE fo what kind of DISEASES ?

Answer 11

cholecystitis
UTI - responsible for all community acquired ecoli
neonatal meningitis
sepsis

Question 12

what is the pathogenesis of ecoli ?

Answer 12

UTI
ecoli that causes UTI are found first n the colon and ass through the stool or migrate to contaminate the urethera
specific sergroups causes this because of the virulence factors such as adhesions - they are not eliminated through urination
also have hemolysin - lysis of erythrocyte and other cells - leading to cytokine response and inflammation