Which of the following is a selective medium for Staphylococcus species?

Mannitol salt agar is a selective medium for Staphylococcus species because it contains a high concentration of salt (7.5% sodium chloride), which inhibits the growth of most other bacteria. This high salt concentration allows for the isolation of salt-tolerant organisms, such as Staphylococcus, which can thrive in this environment.

Additionally, mannitol salt agar contains mannitol as a fermentable carbohydrate and phenol red as a pH indicator. Staphylococcus aureus can ferment mannitol, leading to a drop in pH that turns the media yellow, indicating its presence. Other staphylococci, like Staphylococcus epidermidis, do not ferment mannitol and would not cause this color change, further allowing for differentiation based on mannitol fermentation.

The other media mentioned do not serve as selective media for Staphylococcus species. Bile esculin agar is selective for enterococcus and some gram-positive organisms, nutrient agar supports growth of a wide variety of non-specific bacteria, and blood agar is used for detecting hemolytic activity among various bacteria rather than for selectivity towards Staphylococcus.