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*Member of ''Enterobacteriacae'' family of Gram-negative bacilli
*Member of ''Enterobacteriacae'' family of Gram-negative bacilli
*Facultative anaerobe
*'''Facultative anaerobe'''
*One of predominant bacterial species in colonic flora
*One of predominant bacterial species in colonic flora
*Colonisation of intestinal tract from environmental sources shortly after birth
*Colonisation of intestinal tract from environmental sources shortly after birth
*Usually motile with flagella and fimbriae
*Usually motile with flagella and fimbriae
*Oxidase negative (do not possess cytochrome C oxidase)
*'''Oxidase negative''' (do not possess cytochrome C oxidase)
*Grow on MacConkey agar (in presence of bile salts), producing pink colonies
*Grow on '''MacConkey agar''' (in presence of bile salts), producing pink colonies
*Haemolytic activity on blood agar characteristic of certain strains
*'''Haemolytic activity'' on blood agar characteristic of certain strains
*Lactose fermenter
*'''Lactose fermenter'''
*Reduce nitrates to nitrites and ferment glucose to produce acid and gas
*Reduce nitrates to nitrites and ferment glucose to produce acid and gas
*Possess a lipopolysaccharide (O) antigen, a flagellate (H) antigen, polysaccharide capsule (K) antigens and fimbrial (F) antigens
*Possess a lipopolysaccharide ('''O''') antigen, a flagellate ('''H''') antigen, polysaccharide capsule ('''K''') antigens and fimbrial ('''F''') antigens
*Epidemiological typing of ''E. coli'' uses antigen combinations, eg. O125:K12:H42
*Epidemiological typing of ''E. coli'' uses antigen combinations, eg. O125:K12:H42
===Pathogenesis===
===Pathogenesis===
*Virulence factors include capsules, endotoxin, enterotoxins and colonisation factors
*<u>Virulence factors</u> include capsules, endotoxin, enterotoxins and colonisation factors
*Capsular polysaccharides produced by some strains prevent phagocytosis and interfere with complement
*Capsular polysaccharides produced by some strains prevent phagocytosis and interfere with complement
*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 e'''ndotoxic 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
*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
*'''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
*'''Siderophores''' are made by certain pathogenic strains, and are responsible for iron aquisition; they include aerobactin and enterobactin