Question

The medium used for detecting Staphylococci in dairy products

• A. MacConkey agar
• B. McClung Toabe agar
• C. Malt Extract agar
• D. Baird Parker agar

Hint:

For Staphylococci, think "Black colonies on Baird Parker." It's the gold standard selective medium that uses egg yolk and potassium tellurite.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Staphylococcus aureus is a significant foodborne pathogen in dairy products, often linked to mastitis in cows or unhygienic handling.
Selective and differential media are required to distinguish S. aureus from other microflora.

Step 2: Detailed Explanation:
1.Baird Parker Agar: This is the internationally recognized selective and differential medium for the isolation and enumeration of coagulase-positive staphylococci (S. aureus).
It contains lithium chloride and tellurite to inhibit other bacteria, and egg yolk emulsion to detect lecithinase and lipase activity.
On this medium, S. aureus produces characteristic black, shiny colonies surrounded by a clear zone (halo).
2.Comparison with other media:
-MacConkey Agar: Used for the isolation of Enterobacteriaceae and coliforms.
-McClung Toabe Agar: Used for the detection of Clostridium species based on lecithinase production.
-Malt Extract Agar: A general-purpose medium for the cultivation of yeasts and molds.
Therefore, Baird Parker agar is the specific medium for Staphylococci.

Step 3: Final Answer:
The medium used for detecting Staphylococci is Baird Parker agar.