The document discusses six pathotypes of E. coli that cause intestinal disease: enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), Shiga toxin-producing E. coli (STEC)/enterohemorrhagic E. coli (EHEC), enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAEC), and diffusely adherent E. coli (DAEC). It provides details on the characteristics, symptoms, and laboratory diagnosis of each pathotype, including their toxins, infectious dose, and methods of detecting them like culture, ELISA, and animal testing. The document also discusses enterohem

1. Sudan University
Faculty of Medical Laboratory Sciences
Master program of Microbiology
Medical Microbiology course
Dr. Mahadi Hassan Mamoud
PhD Medical Microbiology

2. six distinct "pathotypes" of E. coli (which cause disease in intestine)
• Enteropathogenic E. coli (EPEC).
• Enterotoxigenic E. coli (ETEC).
• Shiga toxin-producing E. coli (STEC)/enterohemorrhagicE. coli (EHEC),
Verocytotoxin-producing E. coli (VTEC).
• Enteroinvasive E. coli (EIEC).
• Enteroaggregative E. coli (EAEC) (EAggEC)
• diffuselyadherentE. coli (DAE)

3. Enteropathogenic E. coli
• EPEC is main cause of infant diarrhea
• Breast-feeding diminishes the incidence of EPEC infection.
• Rapid person-to-person spread may occur.
• After infection with EPEC there is loss of microvilli.
• Symptoms : Fever, Diarrhea (NO Blood), Vomiting, Nausea.
• Confirm with Polyvalent and monovalent sera.

4. Enterotoxigenic E. coli
• ETEC is a major cause of endemic diarrhea in children
during the first 3 years of life.
• ETEC is the most common agent of traveler's diarrhea.
• There is production enterotoxin
• Produce Heat stable /Heat labile toxins.
• Present with Nausea, Vomiting and Lose stool

5. Enterotoxigenic E.coli
•Laboratory Diagnosis
Demonstration of Enterotoxin LT and ST
Tissue culture tests.
ELISA.
Passive agglutination tests.
Animal experiments inRabbit ileal looptest.
Con.

6. Enteroinvasive E. coli EIEC
a relativelyuncommoncauseof diarrhea.
Some are non motile strains.
 EIEC sharesmany genetic andclinical featureswith
Shigella.
The diseaseresembles the shigellosis
 The difference
EIECproduces disease only at a large inoculum(108 to
1010 CFU8), with onset generallyoccurringafter an
incubationperiod of 1 to 3 days.

7. Enteroinvasive E. coli EIEC
Sereny test:
• Instillationof a suspension of freshly isolated EIEC or Shigella
into theeyes of guineapigs leads to mucopurulent
conjunctivitis and severe keratitis.
• Mice can also be used.
CellPenetrationin HeLa or HEP-2 cells.
Plasmid detection:
VMA ELISA: The plasmid codes for outer membraneantigens
called the virulence markerantigens(VMA) which can be
detected by the ELISA (VMA ELISA) test.
Con.

8. Enterohemorrhagic E.coli
Produce Verocytotoxin or shiga like toxin
• Named so because it was first detected by its cytotoxic effecton
Vero cells, a cellline derived from African green monkeykidney
cells.
• It is also known as SLT = shiga liketoxin because it is similar to
the shigella dysenteriae type 1 toxin in its physical, antigenic
and biological properties
Mild diarrhea - can be fatalhemorrhagic colitis. and uremic
syndrome.
Presentin Human and Animal feces.
Hemorrhagic complication withO157 in Japan and USA.

9. Lab. Diagnosis
o Culture
o DNA detection methods
o Cytotoxic effects on Vero cells.
o Detection with monovalent sera O157/H7
Enterohemorrhagic E.coli Con.

10. Dr.T.V.Rao MD 10

11. • Haemolytic anaemia
• Acute renal failure
• Thrombocytopenia
The verotoxin enters the blood stream
EnterohemorrhagicE.colican cause Haemolytic
Uremic Syndrome HUS
Enterohemorrhagic E.coli

12. Enteroaggregative and Diffusely Adherent E.
Coli EAEC and DAEC
 primarily in developing countries and in young children.
 These strains can cause traveler's diarrhea.
 A largeinoculum is required for infection.
 In vitro, the organisms exhibit a diffuse or "stacked-brick"
adherence pattern.
 Can cause Diarrhea Detect by Culture methods
 Brick-like aggregates on cell surfaces
 Mucus biofilm inhibits fluid absorption
 Diarrhea
 Detection of Enterotoxin

13. • Microscopy
• make distinction is between inflammatory and noninflammatory disease
• Culture
• Identification ofserotypes/pathotypes
 Usuallyperformed atreference lab
 TheE.coliisolate treated ,standardized andallowedto react with antisera (knownantibodies) in
antigenantibodyreactions
 anddesignated
 Specialtests to detect LT and ST are notavailablein mostclinicallaboratories
 Serological characters:
 Somatic(O) antigen.
 Flagellar (H) antigen.
 Manystrainshave capsular(K) antigen.

14. Lab Diagnosis
• Grossly bloody or mucoidstool suggests aninflammatory
process.
• A test for fecal leukocytes (preparation of a thin smear of stool
on a glass slide, addition of a drop of methyleneblue,and
examinationof the wet mount)can suggestinflammatory
disease in patientspresentingwithdiarrhea,
• A testfor fecal lactoferrin, whichis a marker of fecal leukocytes,
is more sensitive and is available in latex agglutinationand
enzyme-linkedimmunosorbentassay formats.

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(Gram stained film of E. coli)

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(E. coli on MacConkey’s agar)

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(Lactose fermenters and non lactose fermenters on
MacConkey’s agar)

19. Reasons E. coli is used for Gene Cloning
• The microorganism Escherichia coli has a long
history of use in the biotechnology industry
and is still the microorganism of choice for
most gene cloning experiments. Although E.
coli is known to the general population for
the infectious nature of one particular strain
(0157:H7) few people are aware of how
versatile and useful E. coli is to genetic
research. There are several reasons E. coli
became so widely used and is still a common
host for recombinant DNA.

20.  Safety
• E. coli is naturally found in the intestinal tracts of humans
and animals where it helps provide nutrients (vitamins K
and B12) to its host. There are many different strains of E.
coli that may produce toxins or cause varying levels of
infection if ingested or allowed to invade other parts of
the body. Despite the bad reputation of one particularly
toxic strain (O157:H7), E. coli are generally relatively
inocuous if handled with reasonable hygiene.