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*''E. coli'' is part of the flora of the large intestine, but is not usually found in the small intestine
*''E. coli'' is part of the flora of the large intestine, but is not usually found in the small intestine
*Some strains possess fimbrae which attach the bacteria to the small intestinal epithelium of particular animal species
*Some strains possess fimbrae which attach the bacteria to the small intestinal epithelium of particular animal species
*''E. coli'' may cause diarrhoea via attaching and effacing lesions, where bacteria adhere intimately to the enterocyte, and cause localised effacement of the brush border microvilli; the epithelial erosion causes dysentery
*''E. coli'' may cause diarrhoea via attaching and effacing lesions, where bacteria adhere intimately to the enterocyte, and cause localised effacement of the brush border microvilli; the epithelial erosion causes dysentery
*Enterotoxigenic ''E. coli'' (ETEC):
*Enterotoxigenic ''E. coli'' (ETEC):
**'Traveller's diarrhoea' in humans
**'Traveller's diarrhoea' in humans
**Oral infection, intestinal colonisation and toxin production
**Oral infection, intestinal colonisation and toxin production
**Fimbrial adhesins allow bacteria to attach to mucosal surfacesin the small intestine and lower urinary tract; this prevents expulsion by peristalsis and flushing of urine
*K88 (F4) is associated with adhesion to the small intestinal mucosa of pigs
*K99 (F5) associated with adhesion in pigs and cattle (these fimbrial adhesins were originally thought to be capsular (K) antigens)
*The fimbrae are encoded by plasmids
**These strains carry a plasmid which encodes an enterotoxin
**These strains carry a plasmid which encodes an enterotoxin
**Two types of enterotoxin: heat-labile (LT) and heat-stable (ST) toxins
**Two types of enterotoxin: heat-labile (LT) and heat-stable (ST) toxins
**The plasmids which produce these toxins are responsible for the pathogenicity of these strains
**The plasmids which produce these toxins are responsible for the pathogenicity of these strains
**Fimbrial antigen or colonisation factor antigens (CFAs)determine species specificity
**Fimbrial antigen or colonisation factor antigens (CFAs)determine species specificity
**LT is an oligometric toxin composed of an enzymatically-active A subunit (30KDa; 2 fragments - A1 and A2) and 5 identical B subunits (12KDa) forming the binding portion (B oligomer)
**LT is an oligometric toxin composed of an enzymatically-active A subunit (30KDa; 2 fragments - A1 and A2) and 5 identical B subunits (12KDa) forming the binding portion (B oligomer)
**It attaches to the brush border of the epithelial cells of the small intestine
**It attaches to the brush border of the epithelial cells of the small intestine
**An adhesin, intimin is required for attchment to enterocytes
**An adhesin, intimin is required for attchment to enterocytes
**Cause attching and effacing lesions in the gut
**Cause attching and effacing lesions in the gut
*Enteroinvasive ''E. coli''
*Enteroinvasive ''E. coli'':
**Dysentry-like strains
**Dysentry-like strains
**Invade epithelial cells by inducing endocytosis
**Invade epithelial cells by inducing endocytosis
**Disseminated intravascular coagulation and thrombus formation
**Disseminated intravascular coagulation and thrombus formation
**''E. coli'' O157:H7 causes haemorrhagic collitis-haemolytic uraemic syndrome in humans
**''E. coli'' O157:H7 causes haemorrhagic collitis-haemolytic uraemic syndrome in humans
*Oedema disease of pigs:
*Oedema disease of pigs: