It is a Gram negative rod shaped bacteria, commonly present in intestinal tract.

1. Escherichia coli
PRESENTED BY
SALOMI.V,
I M.SC MICROBIOLOGY,
SACRED HEART COLLEGE,
TIRUPATTUR,
TAMIL NADU,
INDIA.

2. Escherichia coli
GENERALCHARACTERISTICS
• Gram’s classification – Gram negative
• Shape – Rod shape (Bacilli)
• Motility – Motile
• Capsule - Absent
• Endospores – Absent
• Respiration – Aerobic/Facultative anaerobic

3. • Optimum Temperature - 37 °C
• Optimum pH – 6 to 7
• Habitat – The primary habitat of Escherichia coli is in the
gastrointestinal (GI) tract of human and many other warm blooded
animals. It is found in the mucus or the epithelium on the wall of
intestine. Most commonly found in the colon of large intestine.
• Discovered by Theodor Escherich (German Physician) from
human colon in 1885.

4. TYPES OF Escherichia coli
a) Enterotoxigenic Escherichia coli (ETEC)
b) Enteropathogenic Escherichia coli (EPEC)
c) Enteroinvasive Escherichia coli (EIEC)
d) Enterohemorrhagic Escherichia coli (EHEC)
e) Enteroaggregative Escherichia coli (EAEC)
f) Uropathogenic Escherichia coli (UPEC)
g) Verotoxin producing Escherichia coli (VPEC)
h) Shiga toxin producing Escherichia coli (STEC)

5. PATHOGENICITY OF Escherichia coli
DISEASE TRANSMISSION
• Escherichia coli infections are mainly
transmitted by ingestion of contaminated food and
water.
INCUBATION PERIOD
3 to 4 Days

6. VIRULENCE FACTORS OF Escherichia coli
i. Adhesins
a) Colonization Factor Antigens (CFA I, CFA II and CFA III)
b) Type 1 Fimbriae
c) P Fimbriae
d) S Fimbriae
e) Intimin (Non-fimbrial adhesin)
f) EPEC Adherence factor.

7. ii. Invasins
a) Hemolysin
b) Shigella-like "invasins" for intracellular invasion and spread.
iii. Motility/Chemotaxis .
a) Flagella
iv. Toxins
a) Heat labile toxin
b) Heat stable toxin
c) Shiga toxin
d) Cytotoxin
e) Endotoxin (LPS)

8. v. Antiphagocytic surface properties
a) Capsules
b) K – Antigens
c) Lipopolysaccharides (LPS)
vi. Defense against Serum bactericidal reactions
a) K – Antigens
b) Lipopolysaccharides (LPS)
vii. Defense against Immune responses
a) Capsules
b) K – Antigens
c) Lipopolysaccharides (LPS)

9. PATHOGENESIS OF Escherichia coli
• Escherichia coli bacteria normally live in the intestines of
people and animals.
• Most Escherichia coli are harmless and actually are an
important part of a healthy human intestinal tract. However,
some E. coli are pathogenic(they can cause illness), either
diarrhea or illness outside of the intestinal tract.

10. • Pathogenic strains of E. coli are responsible for three types of
infections in humans:
Urinary tract infections (UTI),
Neonatal meningitis, and
Intestinal diseases (Gastroenteritis).
• The diseases caused (or not caused) by a particular strain of
Escherichia coli depend on distribution and expression of an array
of virulence determinants, including Adhesins, Invasins, Toxins and
abilities to withstand host defenses.

11. LABORATORY DIAGNOSIS OF Escherichia coli
MICROSCOPIC EXAMINATION
• Gram staining – Pink coloured Gram negative rods
• Motility test - Motile
COLONY MORPHOLOGY ON CULTURE MEDIUM
• Nutrient agar - Colonies are large, thick, greyish white, moist,
smooth, opaque or translucent.
• MacConkey agar – Pink coloured Lactose fermenting colonies.
• Eosin Methylene Blue (EMB) - Selective medium for Escherichia
coli. In EMB agar, Escherichia coli shows Metallic sheen production.
• Salmonella Shigella Agar (SSA) – Pink colonies are produced

12. BIOCHEMICAL TESTS
a) Catalase test – Positive
b) Oxidase test - Negative
c) Urease test – Negative
d) Indole test - Positive
e) Methyl Red (MR) test – Positive
f) Voges Proskauer (VP) test - Negative
g) Citrate utilization test – Negative
h) TSI Test – Acid butt, Acid slant and Gas production observed

13. TREATMENT AND PREVENTIVE MEASURES
Antibiotic Therapy
• Enteric pathogens are treated symptomatically unless disseminated
disease occurs.
• Antibiotic therapy is guided by invitro susceptibility tests.
• Escherichia coli meningitis requires antibiotics, such as Third - Generation
Cephalosporins (e.g.,Ceftriaxone).
• Escherichia coli sometimes leads to Pneumonia and it requires
a) Respiratory support
b) Adequate oxygenation
c) Antibiotics, such as Third Generation Cephalosporins or
Fluoroquinolones.

14. Vaccination and Preventive measures
• Appropriate infection-control practices are used to reduce the
risk of nosocomial infections (e.g., restricting use of antibiotics, avoiding
unnecessary use of urinary tract catheters).
• Maintenance of high hygienic standards to reduce the risk of
exposure to gastroenteritis strains.
• Proper cooking of beef products to reduce risk of Escherichia coli
infections.

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