Question

Urinary tract infections are commonly caused by Staphylococcus saprophyticus and Escherichia coli, less commonly caused by Proteus mirabilis. You have a mixed culture of these pathogens, which you inoculate onto both MacConkey agar and nutrient agar, and then you incubate the plates at optimal growth conditions. On the MacConkey agar, E. coli appears pink, P. mirabilis appears colorless, and S. saprophyticus does not grow. All three microorganisms appear cream on the nutrient agar plate. What is the best explanation for this data?

Answer 1

It tells that Macconkey agar is both selective as well as differential media.

Step-by-step explanation:

Macconkey media can differentiate both particular species as well as group of closely related species too, which makes it both differential as in case of growth of both E.coli & P.mirabillis. And colored growth of E.coli shows that it is a gram negative and could ferment lactose.