Question

If you wanted to isolate S. aureus from a pus specimen containing mixed flora, what medium would you choose to get results more rapidly? Why?

A) Blood Agar, for its differential properties.
B) Nutrient Agar, for general microbial growth.
C) Mannitol Salt Agar, for selective isolation.
D) MAC Agar, for lactose fermentation.

Answer 1

To isolate S. aureus from a pus specimen containing mixed flora, Mannitol Salt Agar (MSA) should be chosen as it is a selective medium for staphylococci and other halotolerant bacteria, inhibiting the growth of unwanted bacteria and allowing differentiation based on mannitol fermentation.

Step-by-step explanation:

If you wanted to isolate S. aureus from a pus specimen containing mixed flora, the medium you should choose to get results more rapidly would be Mannitol Salt Agar (MSA) because it is a selective medium for staphylococci and other halotolerant bacteria. The high concentration of salt (7.5%) inhibits the growth of bacteria susceptible to osmotic stress, while the presence of mannitol and phenol red allows for the differentiation of bacteria based on their ability to ferment mannitol.