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*Most strains have low virulence
*Most strains have low virulence
*Found in many non-specific, endogenous infections, eg. wound infections and upper respiratory tract infections and septicaemia
*Found in many non-specific, endogenous infections, eg. wound infections and upper respiratory tract infections and septicaemia
*Also and enteropathogen
*Also an enteropathogen, causing neonatal diarrhoea in young animals and enteric colibacillosis
*Pathogenic strains possess virulence factors allowing colonisation of mucosal surfaces
*Pathogenic strains possess virulence factors allowing colonisation of mucosal surfaces
*Endotoxin is a lipolysaccharide component of the cell wall of Gram-negative bacteria, composed of lipid A, a core polysaccharide and various side chains
*Endotoxin is a lipolysaccharide component of the cell wall of Gram-negative bacteria, composed of lipid A, a core polysaccharide and various side chains
*Endotoxin is realeased when bacteria die, and causes endothelial damage leading to disseminated intravascular coagulation and endotoxic shock; it is also a pyrogen
*Endotoxin is realeased when bacteria die, and causes endothelial damage leading to disseminated intravascular coagulation and endotoxic shock; it is also a pyrogen
*
*Enterotoxins, verotoxins and cytotoxic necrotising factors produced by many pathogenic ''E. coli''; these produce cell damage at their site of action
*Alpha-haemolysin may increase iron availability for invading organisms
*Siderophores are made by certain pathogenic strains, and are responsible for iron aquisition; they include aerobactin and enterobactin
===Extra-intestinal infection===
===Extra-intestinal infection===
*K99 (F5) associated with adhesion in pigs and cattle (these fimbrial adhesins were originally thought to be capsular (K) antigens)
*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
*The fimbrae are encoded by plasmids
*''E. coli'' may cause diarrhoea via attaching and efacing lesions, where bacteria adhere intimately to the enterocyte, and cause localised effacement of the brush border microvilli
*''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'':
*Enterotoxigenic ''E. coli'' (ETEC):
** Contributes to [[Intestines - Catarrhal Enteritis#Undifferentiated Neonatal Calf Diarrhoea|undifferentiated neonatal calf diarrhoea]], a mixed viral enteritis in calves
** Contributes to [[Intestines - Catarrhal Enteritis#Undifferentiated Neonatal Calf Diarrhoea|undifferentiated neonatal calf diarrhoea]], a mixed viral enteritis in calves
**Causes scours in pigs and calves
**Causes scours in pigs and calves
**ST is not immunogenic; it is small, with only 19 amino acids
**ST is not immunogenic; it is small, with only 19 amino acids
**ST activates guanylate cyclase in enteric epithelial cells, stimulating fluid secretion
**ST activates guanylate cyclase in enteric epithelial cells, stimulating fluid secretion
*Enteropathogenic ''E. coli'':
*Enteropathogenic ''E. coli'' (EPEC):
**Possess ''E. coli'' adherencefactor plasmid
**Possess ''E. coli'' adherence factor plasmid
**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''
**Associated with oedema disease toxin-producing strains of ''E. coli''
**Associated with oedema disease toxin-producing strains of ''E. coli''
**Verotoxin released in the small intestine and carried in the bloodstream
**Verotoxin released in the small intestine and carried in the bloodstream
**Haemolysin production
*Haemorrhagic gastroenteritis:
*Haemorrhagic gastroenteritis: