How would you determine whether a colorless colony on MacConkey agar is Salmonella or Shigella? Why...

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Biology

How would you determine whether a colorless colony on MacConkeyagar is Salmonella or Shigella? Why would you want to identify acolorless colony? Briefly explain

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Salmonella has Lysine DeCarboxylase whereas Shigella does not Shigella is a gram negative rod found in natural habitat of intestinal tract of humans and other primates The major pathogen is Shigella dysenteriae but Shigella sonnei is more common in the US It causes dysentery which is an invasive bloody diarrhea Shigella is facultative anaerobe but grows best aerobically and is a nonlactose fermenter so will have colorless colonies on MacConkey agar Hektoen enteric agar green colonies Hektoen enteric agar Selective medium selective growth of SalmonellaShigella contains deoxycholate which suppresses other Enterobacteriaceae and Gram positive bacteria Differential medium distinguishes Shigella green colonies since no H2S production from Salmonella black colonies since have H2S production Shigella is nonmotile and Produces heatlabile exotoxin called Shiga toxin whereas salmonella is motile Shigella acts as enterotoxin and See Answer

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