Escherichia coli
Morphology
Belongs to Enterobacteriaceae - A complex family of organisms
Gram-negative
Facultative anaerobe
Commonly present in large intestine
Named after Theodor Escherich a German physician
There are more than 700 different serotypes of E. coli
Rod shaped
Usually motile - peritrichous flagella
Some produce polysaccharide capsules
Non sporing , Non acid fast
1-3 X 0.4 -0.7 microns
Appear in singles or in pairs
Escherichia coli
Some are non pathogenic
A few are highly Pathogenic
Some commensals turn out to be pathogenic
Detection of E.coli in water indicates pollution and contamination.
Grow well on non- selective media
Form smooth, colourless colonies 2-3 mm in diameter in 18h on nutrient agar
Temperature: 15-45℃
Normal flora of the mouth and intestine
Colonizes newborns GIT within hours after birth
Lives in the intestines of people and animals
Mostly harmless bacteria - Assists in digestion
Produces vitamins B12 and K (Non pathogenic)
Protects the intestinal tract from bacterial infection
Biochemical Characteristics
Glucose, Lactose, Mannitol, Maltose fermented with A/G
Indole +
Methyl Red +
Voges Proskauer – ve
Citrate –ve
Urease not produced
Esherichia coli
, Raw produce, wildlife, livestock, and humans are particularly susceptible to E.
Coli
Different types of E. coli contaminate different types of foods
Ingesting food or water contaminated with E. Coli cause mild to severe GI
illness
Some pathogenic E. Coli --- Shiga toxin-producing E.Coli (STEC) can be life-
threatening
Foods Linked to outbreaks of E. coli
Leafy greens
Sprouts
Raw milk
Cheeses
Raw beef and poultry
Transmission
Food sources:
Raw fruits and vegetables, sprouts, leafy vegetables
Undercooked meat
Unpasteurized milk and juices
Fermented dried meat products
Environmental sources:
Fecal-contaminated lakes
Non-chlorinated municipal water supply – drinking and swimming
Pet and farm animals
Unhygienic person to person contact- Diaper changing
Improper sanitation - Day care and chronic adult care facilities
Pathogenic Strains
Enterohaemorrhagic E. coli (EHEC)
Enterotoxigenic E. coli (ETEC)
Enteroinvasive E. coli (EIEC)
Enteropathogenic E. coli (EPEC)
Enterohaemorrhagic E.coli
Pathogenic to humans
Infection occurs via faecal-oral route
Produce cytotoxins that disrupt protein synthesis in host cells
The toxins are also called verocytotoxins or Shiga like toxins – attach to the
epithelial cells producing lesions
Morphology
Belongs to Enterobacteriaceae - A complex family of organisms
Gram-negative
Facultative anaerobe
Commonly present in large intestine
Named after Theodor Escherich a German physician
There are more than 700 different serotypes of E. coli
Rod shaped
Usually motile - peritrichous flagella
Some produce polysaccharide capsules
Non sporing , Non acid fast
1-3 X 0.4 -0.7 microns
Appear in singles or in pairs
Escherichia coli
Some are non pathogenic
A few are highly Pathogenic
Some commensals turn out to be pathogenic
Detection of E.coli in water indicates pollution and contamination.
Grow well on non- selective media
Form smooth, colourless colonies 2-3 mm in diameter in 18h on nutrient agar
Temperature: 15-45℃
Normal flora of the mouth and intestine
Colonizes newborns GIT within hours after birth
Lives in the intestines of people and animals
Mostly harmless bacteria - Assists in digestion
Produces vitamins B12 and K (Non pathogenic)
Protects the intestinal tract from bacterial infection
Biochemical Characteristics
Glucose, Lactose, Mannitol, Maltose fermented with A/G
Indole +
Methyl Red +
Voges Proskauer – ve
Citrate –ve
Urease not produced
Esherichia coli
, Raw produce, wildlife, livestock, and humans are particularly susceptible to E.
Coli
Different types of E. coli contaminate different types of foods
Ingesting food or water contaminated with E. Coli cause mild to severe GI
illness
Some pathogenic E. Coli --- Shiga toxin-producing E.Coli (STEC) can be life-
threatening
Foods Linked to outbreaks of E. coli
Leafy greens
Sprouts
Raw milk
Cheeses
Raw beef and poultry
Transmission
Food sources:
Raw fruits and vegetables, sprouts, leafy vegetables
Undercooked meat
Unpasteurized milk and juices
Fermented dried meat products
Environmental sources:
Fecal-contaminated lakes
Non-chlorinated municipal water supply – drinking and swimming
Pet and farm animals
Unhygienic person to person contact- Diaper changing
Improper sanitation - Day care and chronic adult care facilities
Pathogenic Strains
Enterohaemorrhagic E. coli (EHEC)
Enterotoxigenic E. coli (ETEC)
Enteroinvasive E. coli (EIEC)
Enteropathogenic E. coli (EPEC)
Enterohaemorrhagic E.coli
Pathogenic to humans
Infection occurs via faecal-oral route
Produce cytotoxins that disrupt protein synthesis in host cells
The toxins are also called verocytotoxins or Shiga like toxins – attach to the
epithelial cells producing lesions
