<prompt> Which of the following is late lactose fermenter ?E coliKlebsiellaSalmonellaShigella sonnei  <response>: Ans. is d i.e., Shigella sonnei Lactose fermenters produce pinkbright red colonies on MacConkeys agar , while lactose non-fermenters produce pale colonies :Lactose fermenters rapid : These are Coliforms, e.g. Escherichia, Klebsiella and Enterobacter aerogenes.Late lactose fermenters slow: These are Shigella Sonnei, Serratia, Citrobacter, Arizona, Providencia and Ervinia.Non-lactose fermenters : Shigella except Shigella Sonnei, Salmonella, Proteus 