Question

Which is not a selective medium but is a differential medium?

• A. Blood agar
• B. Mannitol salt agar
• C. Mac Conkey agar
• D. Eosin methylene blue agar

Hint:

Blood agar is used to differentiate organisms based on hemolysis patterns but does not inhibit other bacteria.

Answer 1

The Correct Option is A

Step 1: Understanding Selective and Differential Media 
Selective media inhibit the growth of some organisms while allowing others to grow. Differential media allow different organisms to be distinguished based on their appearance. 
Step 2: Evaluating the Options 
- Blood agar: It is a differential medium but not selective. It distinguishes bacteria based on their hemolytic properties. 
- Mannitol salt agar: Selective for Staphylococcus species and differential for mannitol fermentation. 
- Mac Conkey agar: Selective for Gram-negative bacteria and differential for lactose fermentation. 
- Eosin methylene blue agar: Selective for Gram-negative bacteria and differential for lactose fermentation. 
Step 3: Conclusion 
Blood agar is a differential medium but not selective, as it does not inhibit the growth of specific organisms.