Morphology Identification Gram-negative non-spore forming rods. When motile, by peritrichous flagella. o Primarily normal flora of gastrointestinal tract. E. coli>klebsiella>proteus>Enterobacter o Free living, also transient colonizers of skin o Facultative anaerobes: mixed acid fermentation o All ferment glucose; all reduce nitrates to nitrites; all oxidase negative o Lactose fermentation: normal flora positive and pathogens negative o Primary isolation media include eosin-methylene-blue (EMB) and mac Conkey agar. o Differential selective media for specific organisms including dyes and bile salts( Salmonella-Shigella(ss)medium, bismuth sulfite media.)Morphology & Identification ⚫ Gram-negative non-spore forming rods. When motile, by peritrichous flagella. ⚫ Primarily normal flora of gastrointestinal tract. E. coli>Klebsiella>Proteus>Enterobacter ⚫ Free living, also transient colonizers of skin. ⚫ Facultative anaerobes: mixed acid fermentation ⚫ All ferment glucose; all reduce nitrates to nitrites; all oxidase negative. ⚫ Lactose fermentation: normal flora positive and pathogens negative. ⚫ Primary isolation media include eosin-methylene-blue (EMB) and MacConkey agar. ⚫ Differential selective media for specific organisms including dyes and bile salts. (Salmonella-Shigella (SS) medium, bismuth sulfite media.)