Examination

of a patient with pustular skin lesions led to the isolation of a causative

agent that forms round, yellow, medium-sized colonies on blood agar, surrounded

by a hemolysis zone. Smears from the colonies contain irregular clusters of

Gram-positive cocci. The culture is oxidase- and catalase-positive, ferments

mannitol, and synthesizes plasmocoagulase. Which causative agent was isolated?