What is often used as a selective medium to identify lactose-fermenting Enterobacteriaceae?

What is often used as a selective medium to identify lactose-fermenting Enterobacteriaceae?

• A. Chocolate agar
• B. MacConkey agar
• C. Minimal media
• D. Bile-Esculin agar

Answer: (B)

MacConkey agar is a selective medium specifically designed to isolate and differentiate lactose-fermenting Enterobacteriaceae from non-lactose fermenters. The medium contains bile salts and crystal violet, which inhibit the growth of Gram-positive organisms, allowing Gram-negative bacteria like Enterobacteriaceae to thrive. Lactose is one of the primary components of MacConkey agar; when lactose is fermented, acidic byproducts are produced that cause a color change in the pH indicator incorporated in the medium. Lactose fermenters, such as Escherichia coli, produce pink colonies due to this pH change, while non-lactose fermenters will remain colorless or result in pale colonies. This distinct visual difference makes MacConkey agar a valuable tool for microbiologists in identifying and characterizing members of the Enterobacteriaceae family, based on their ability to ferment lactose. In contrast, the other options listed are not selective for lactose fermentation in the same way.

MacConkey agar is a selective medium specifically designed to isolate and differentiate lactose-fermenting Enterobacteriaceae from non-lactose fermenters. The medium contains bile salts and crystal violet, which inhibit the growth of Gram-positive organisms, allowing Gram-negative bacteria like Enterobacteriaceae to thrive.

Lactose is one of the primary components of MacConkey agar; when lactose is fermented, acidic byproducts are produced that cause a color change in the pH indicator incorporated in the medium. Lactose fermenters, such as Escherichia coli, produce pink colonies due to this pH change, while non-lactose fermenters will remain colorless or result in pale colonies. This distinct visual difference makes MacConkey agar a valuable tool for microbiologists in identifying and characterizing members of the Enterobacteriaceae family, based on their ability to ferment lactose. In contrast, the other options listed are not selective for lactose fermentation in the same way.