Which of the following is a characteristic of Staphylococcus aureus?

• A. DNase negative
• B. Coagulase negative
• C. Mannitol fermentation positive
• D. Growth inhibition in presence of increased salt

Answer: (C)

Staphylococcus aureus is known for fermenting mannitol, which is what this characteristic tests on mannitol salt agar. When it ferments mannitol, acid is produced and the medium becomes yellow, helping to distinguish S. aureus from other staphylococci. This organism is coagulase-positive and DNase-positive, and it tolerates high salt, so it grows in salty conditions rather than being inhibited by them. Therefore, a positive mannitol fermentation is the best match. The other traits described don’t fit: it is not DNase negative, not coagulase negative, and it does not have growth inhibition in high salt.