A young butcher cuts his forearm with a knife. Over the next week, he notices swelling, redness, and warmth at the site. Four days later, he presents to the emergency depament with fever, shaking chills and severe lower back pain. Physical examination reveals a temperature of 39.4 C (102.9 F), swelling in his forearm with an area of central softness, and tenderness to pressure over his lower spine. Laboratory data show a leukocyte count of 14,000/mm3 with 81% polymorphonuclear leukocytes. Blood cultures grew a gram positive cocci in clusters on blood agar; colonies show a yellow pigment, and the organism is positive on mannitol/salt agar. The organism is catalase and coagulase positive. Which of the following is the most likely pathogen?