Escherichia coli (E. coli) is a common bacterium that lives in the intestines of humans and animals. Certain strains of E. coli can cause illness. E. coli is characterized as a gram-negative, rod-shaped, facultative anaerobe that ferments glucose and lactose. Different pathogenic strains include enterotoxigenic E. coli (ETEC) which produces heat-labile and heat-stable enterotoxins causing travelers' diarrhea; enteroaggregative E. coli (EAEC) associated with acute and chronic diarrhea producing a heat-stable toxin; and enterohemorrhagic E. coli (EHEC) which causes bloody diarrhea and potentially hem

1. Overview on Escherichia Coli
Prepared by
Ripu chandra das
Noakhali science & technology university.

2. Here we will discuss about
Escherichia coli and it’s….
1.Characteristics.
2.Toxin.
3.Virulence factor.
4.Mechanism.
5.Food intoxication.
6.Disease and Symptoms.
7.Prevention.
8.Treatment.

3. Characteristics of Escherichia coli.
 Gram negative bacteria.
 Motile or non-motile, rod shaped.
 Non-spore forming.
 Facultative anaerobic.
 Oxidase (-ve), Indole test (+ve).
 Ferment glucose & lactose.
 Normal flora of intestine.
 Opportunistic pathogens.
 Grows in MacConkey agar.

4. Different strains of E.coli
HEAT labile enterotoxin
• LT is large (84’000Da), immunogenic
oligotoxin, related to cholera toxin in
sequence.
• AB toxin; two common proteins.
• Adenylate cyclase activation.
Heat stable enterotoxin
• A small polypeptide (2000 Da)’ non
immunogenic in it’s natural form.
• Encoded on transmissible plasmid.
• Activation of guanylate cyclase.
1.Enterotoxigenic E . coli (ETEC)
o Found in raw meat products’ vegetables and water.
o ETEC is most common pathogen causing traveler’s diarrhea.
o Produce Heat labile and Heat stable enterotoxins.

5. 2.Enteroaggregative E. coli (EAEC)
o Associated with acute and chronic watery diarrhea.
o It releases a Heat-stable Enterotoxin 1 (EAST1).
o This EAST1 induce diarrhea in human.
o Also play important role in the pathogenicity of EAEC.
3.Enterohemorrhagic E. coli (EHEC)
o EHEC is a strain of E. coli that produce a toxin called Shiga toxin.
o It cause bloody diarrhea.
o Normally found in the intestine of healthy cattle.

6. Virulence Factor
ETEC strain:
1.Adhesins: 2 types.
I. type 1 pili .
II. & CFA (Colonization Factor Antigen) : CFA1, CFA2(flexible fimbriae associated with CS antigen
CS3), CFA3(bundle forming pilus), CFA4(maturation of different type of fimbriae).
2. Enterotoxin:
I. Heat-labile ( LT): LT1 and LT2
II. Heat-stable (ST): STa and STb
EAggEC strain:
1. Adhesin :
I. Fimbriae like structure.
II. Aggregative.
III. GVVPQ fimbriae
2. Enterotoxin: ST like toxin called “ EAST”.
EHEC strain:
1. Adhesins .
2. Toxin: Shiga toxin.

7. Mechanism
• For ETEC LT toxin-
LT1 has same structure and
the same mechanism of action
as cholera toxin. 5 B subunit
and 1 A subunit.
B subunits of LT bind to host cell
antigen GM & the A subunit is
internalized
Inside the cell, the A subunit of
the toxin ADP-ribosylates Gs.
Thus, CFTR activated by the
rising of cAMP concentration.
Thus, CFTR activated by the
rising of cAMP concentration.
Increasing Cl secretion inhibit
the uptake of NaCl.
The ion imbalance causes
intestinal cells to lose control of
the flow of water, resulting in loss
of water from tissues & diarrhea
occur.

9. Mechanism
• ETEC STa toxin-
STb toxin-
oIt has different amino acid sequence that Sta. It has been found only in porcine ETEC strain &
is uncertain whether it contributes to human intestinal disease.
The receptor for Sta is host cell guanylate cyclase that
regulates the levels of intracellular cGMP.
It causes an increase in the cGMP level in the host
cytoplasm that leads to fluid loss same as cAMP.

10. Mechanism
• for (EHEC)
The attachment of bacterial
fimbriae to enterocyte.
Then, bacterialTir translocated to
enterocyte. (Tir=Translocated
intimin receptor)
Then the binding ofTir to intimin
is occurred
Then Shiga toxin enter
enterocytes and stop protein
synthesis.
Then it release the Shiga toxins
Then the Shiga toxins bind to
Gb3/GB4 receptors of
enterocyte.
This leads to damage and
death of enterocyte which can
lead to bloody diarrhea
Shiga toxins can enter the
blood circulations.
Toxins to damage RBC’s
platelets, kidneys, brain and
possible death.

12. Mechanism
• Enterotoxins of EAgg EC-
Produce ST like toxin ‘EAST’ similar to ETEC which forms pores in
host cell membrane.
Binding of this to HEP-2 cells causes increase calcium level in the
host cell, through the pore.
Changes in calcium levels have a number of effects on cellular
function.

13. Diseases and Symtoms
1. Diarrheal diseases:
Enteropathogenic E.coli
(EPEC) causes diarrhea of
infants. Enterotoxigenic E.
coli (ETEC) causes traveler’s
diarrhea. Enteroaggregative
E. coli (EAEC) causes acute
and chronic diarrhea.
Symptoms:
I. Weight loose, watery stool.
II. Abdominal cramps and
abdominal pain.
III. Bloating.
IV. Nausea.
V. Urgent need to have bowel
moment.
• 2. Hemorrhagic colitis and Hemolytic uremic
syndrome: Enterohemorrhagic E. coli (EHEC)
causes hemorrhagic colitis (HC) or bloody
diarrhea that can progress to the potentially
hemolytic uremic syndrom (HUS).
• Symptoms:
I. Bloody diarrhea
II. Decreased urination or blood in the urin.
III. Abdominal pain, vomiting and occasionally fever.
IV. Pallor.
V. Small, unexplained bruises or bleeding from the
nose and mouth.
VI. Fatigue and irritability.
VII. Confusion and seizures.
VIII. High blood pressure.

14. Diseases and symptoms
3. Shiga toxin producing E.coli infection: STEC produces a toxin that damages the
lining of the small intestine often leading like symptoms. Like…….
I. Watery diarrhea.
II. Nausea.
III. Dehydration.
IV. Severe stomach cramp.
V. Fatigue.
VI. Potentially feeling an unge to defecate beat being unable to.

15. Foodborne intoxication
 A minority of the strains cause illness in human. Certain strain of E. coli are
responsible for infant diarrhea and gastroenteritis. E. coli that are responsible for the
numerous reports of contaminated foods and beverages are those that produce
SHIGA toxin.
SHIGATOXIGENIC Escherichia coli (STEC) and virotoxigenic E. coli (VTEC), are strains
of E. coli that produce either SHIGA toxin or Shiga like toxin (Virotoxin). These toxin
produced in food cause foodborne illness.
Another strain of E. coli EHEC are major causes of foodborne illness. When infecting
humans, they often cause gastroenteritis, enterocolitis and bloody diarrhea and
sometimes cause a severe complication called hemolytic-uremic syndrome (HUS).

16. Prevention
Washing hand properly before preparing foods , touching any
materials of baby. Also after used bathroom, change diaper,
contact with animals and handling raw materials.
Also prevent infection by being careful about the foods that have
very chance of contamination.
Always drink pasteurized milk, juice and cider. Wash all of food
products before preparing and eat.
Raw products always cooked at proper temperature to prevent E.
coli infection.
During swimming in pool, lake or ocean try not to sallow the
water.

17. Treatment
There is no exact cure for E. coli infection. Patients loss a lot of
water through vomiting, diarrhea, so required to drink a lot of
water to prevent dehydration.
In E. coli treatment fluid replacement therapy used where 0.9%
NaCl solution are used. By this fluid replacement body has to
resolve itself.
Antibiotics are not recommended for E. coli Infection because it
causes some serious risk of complication Hemolytic uremic
syndrome . (HUS)
Over the counter (OTC) drugs should not be taken during
diarrhea, because it slows down patients digestive system that
delay to eliminate E. coli infection.

18. THANK YOU