Properties of E. coli

Important Properties of E. coli

1. Gram staining test: Gram Negative short rods
2. Most abundant facultative anaerobe in colon and feces
3. Lactose fermenter (This property distinguishes it from Salmonella and Shigella-two most common intestinal pathogen)
4. Antigenic properties: There are more than 1000 antigenic types of Escherichia coli. 
   a. O-Cell wall antigens (>150 types)
   b. H- Flagellar antigen (>50 types)
   c. K- capsular antigen (>90 types)

Features of E.coli which helps for Laboratory diagnosis

1. E.coli, ferments lactose and produces pink colonies in MacConkey Agar.  (E.coli O157:H7) does not ferment sorbitol, which serves as an important criterion that distinguishes it from other strains of E.coli
2. On EMB agar, E coli produces characteristics green sheen
3. Indole positive: produces indole from tryptophan
4. It decarboxylates lysine
5. it uses acetate as only source of carbon
6. It is motile

 

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