Enterobacteriacae is classfied based on?

Ans. is 'd' i.e., Lactose fermentation Initially Enterobacteriacea was classifed on the bases of their lactose fermenting ability on MacConkey's medium, the most popular medium for the isolation of fecal bacilli. Lactose fermenters produce pink/bright red colonies on MacConkey's agar , while lactose non-fermenters produce pale colonies : i) Lactose fermenters (rapid) : These are Coliforms, e.g. Escherichia, Klebsiella and Enterobacter aerogenes. ii) Late lactose fermenters (slow) : These are Shigella Sonnei, Serratia, Citrobacter, Arizona, Providencia and Ervinia. iii) Non-lactose fermenters : Shigella except Shigella Sonnei, Salmonella, Proteus.