Question

multiple choice question this medium, macconkey agar, has colonies that appear either red or white based on their ______. ability to ferment lactose antibiotic susceptibility reaction in the gram stain ability to lyse blood cells copyright © mcgraw hill llc. permission required for reproduction or display. 30 of 80 concepts completed

Explanation:

MacConkey agar is a differential medium used to distinguish between lactose - fermenting and non - lactose - fermenting bacteria. Lactose - fermenting bacteria produce acid during lactose fermentation, which causes the colonies to appear red (due to the pH - indicator in the medium), while non - lactose - fermenting bacteria form white colonies. Antibiotic susceptibility is tested using methods like the Kirby - Bauer disk diffusion test, not MacConkey agar. The Gram stain reaction is determined by the Gram staining procedure, not by colony appearance on MacConkey agar. The ability to lyse blood cells is tested on blood agar, not MacConkey agar. So the correct factor is the ability to ferment lactose.

Answer:

A. ability to ferment lactose